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Video: Is silodosin your best option when selecting the right α-blocker?

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A significant proportion of aging men will have bothersome LUTS and will eventually seek help for this problem. Various medical therapies are available to help aleviate these symptoms. Amongst the various treatments, α-blockers are some of the most widely used drugs. Novara et al. [1] recently published a report on the efficacy and safety of silodosin in a pooled analysis of individual patient data from three registrational randomized controlled trials comparing silodosin and placebo in patients with LUTS. Their study contributes pertinent information to aid the clinician in determining which α-blocker is best suited for specific patients with LUTS.

In the current study, patients were subdivided into groups in order to better understand which patient would benefit most from the use of silodosin [2]. In addition, the article examines the safety of silodosin in these same distinct patient groups. With regard to efficacy, silodosin was significantly more effective than placebo in improving all IPSS-related variables and maximum urinary flow rate, regardless of the patient’s age. When comparing the efficacy of silodosin in different age groups, no difference was observed for any of the IPSS variables, whereas patients aged <65 years had a statistically significantly greater maximum urinary flow rate.

With regard to safety, silodosin was associated with a significantly higher adverse event (AE) rate compared with placebo. When comparing the safety of silodosin in patients aged <65 years and >65 years, the overall AE rate, ejaculatory dysfunction and discontinuation rate attributable to AEs were all higher in the younger age group. Interestingly, in patients with concomitant use of antihypertensive drugs, the use of silodosin was not associated with a higher risk of either dizziness or orthostatic hypotension.

In a previous study by the same authors, no clinically relevant or statistically significant differences with regard to diastolic blood pressure, systolic blood pressure or heart rate in patients taking silodosin as compared to placebo were found [3]; however, a minor statistically significant difference vs placebo was observed with tamsulosin. The present study by Novara et al. [2] further supports the belief that silodosin is a safe drug from a cardiovascular standpoint.

From a sexual standpoint, silodosin does not seem to perform as well. In the present study, patients in the silodosin group had significantly more adverse events as compared with the placebo group. Retrograde ejaculation was by far the most common side effect affecting 32.8% of patients aged <65 years vs 0.9% in the placebo group. Similarly, in a study by Chapple et al. [3], as many as 14.2% of patients in the silodosin treatment group had ejaculatory dysfunction, compared with 2.1 and 1.1% of patients in the tamsulosin and placebo treatment groups, respectively. Although the percentage of patients who discontinued treatment because of treatment-emergent AEs in the present study was small and not significantly different among all treatment groups, one might hypothesize that over a longer follow-up period, such a prevalent side effect could be responsible for a higher discontinuation rate. Consequently, it should be kept in mind that for patients desiring to maintain antegrade ejaculation, or who are bothered by treatment-onset ejaculatory dysfunction, especially younger patients, silodosin might not be the best treatment option. Furthermore, it should be recognized that some patients would potentially accept a reduction in treatment efficacy to preserve ejaculation [4].

With regard to clinical outcomes, few published papers comparing tamsulosin with silodosin are available [5, 6]. One article found no clinically significant difference between the two α-blockers [5] whereas the other, which was a post hoc analysis, found a marginal clinical benefit for silodosin over tamsulosin [4]. Unfortunately, head-to-head trials are not forthcoming, so it will not be possible to determine if one α-blocker is clinically better than the other. Furthermore, the present study, because it lacked an active control arm, did not compare silodosin with tamsulosin, which leaves something to be desired.

In conclusion, careful consideration should be given to specific patient characteristics such as age and comorbidities, along with personal preferences towards sexual function when offering patients α-blockers for treatment of LUTS.

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Hugo Lavigueur-Blouin and Naeem Bhojani

 

Department of Urology, Centre Hospitalier de l’Universite de Montreal, Montreal, QC, Canada

 

References

 

1 Novara G, Chapple CR, Montorsi F. A pooled analysis of individual patient data from registrational trials of silodosin in the treatment of non-neurogenic male lower urinary tract symptoms (LUTS) suggestive of benign prostatic hyperplasia (BPH). BJU Int 2014; 114: 427–33

 

2 Novara G, Chapple CR, Montorsi F. Individual patient data from registrational trials of silodosin in the treatment of non-neurogenic male lower urinary tract symptoms (LUTS) associated with benign prostatic hyperplasia (BPH): subgroup analyses of efficacy and safety data. BJU Int 2015; 115: 802–4

 

3 Chapple CR, Montorsi F, Tammela TL et al. Silodosin therapy for lower urinary tract symptoms in men with suspected benign prostatic hyperplasia: results of an international, randomized, double-blind, placebo- and active-controlled clinical trial performed in Europe. Eur Urol 2011; 59: 342–52

 

4 Sturch P, Woo HH, McNicholas T, Muir G. Ejaculatory dysfunction after treatment for lower urinary tract symptoms: retrograde ejaculation or retrograde thinking? BJU Int 2014. doi: 10.1111/bju.12868

 

5 Montorsi F. Profile of Silodosin. Eur Urol Suppl 2010; 9: 491–5

 

6 Novara G, Tubaro A, Sanseverino R et al. Systematic review and meta-analysis of randomized controlled trials evaluating silodosin in the treatment of non-neurogenic male lower urinary tract symptoms suggestive of benign prostatic enlargement. World J Urol 2013; 31: 997–1008

 

Article of the Month: Have TRP channels fulfilled their promise in LUTS?

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Every Month the Editor-in-Chief selects the Article of the Month from the current issue of BJUI. The abstract is reproduced below and you can click on the button to read the full article, which is freely available to all readers for at least 30 days from the time of this post.

In addition to the article itself, there is an accompanying editorial written by a prominent member of the urological community. This blog is intended to provoke comment and discussion and we invite you to use the comment tools at the bottom of each post to join the conversation.

Finally, the third post under the Article of the Month heading on the homepage will consist of additional material or media. This week we feature a video from Dr. Wouter Everaerts, discussing his paper. 

If you only have time to read one article this week, it should be this one.

Transient receptor potential channel modulators as pharmacological treatments for lower urinary tract symptoms (LUTS): myth or reality?

Yves Deruyver*‡¶, Thomas Voets†¶, Dirk De Ridder*‡¶ and Wouter Everaerts*§¶

 

*Laboratory of Experimental Urology, Department of Development and Regeneration,† Laboratory for Ion Channel Research, Department of Molecular Cell Biology, KU Leuven, ‡University Hospitals Leuven, TRP Research Platform Leuven (TRPLe), Leuven, Belgium, and §Royal Melbourne Hospital, Melbourne, Australia

 

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Transient receptor potential (TRP) channels belong to the most intensely pursued drug targets of the last decade. These ion channels are considered promising targets for the treatment of pain, hypersensitivity disorders and lower urinary tract symptoms (LUTS). The aim of the present review is to discuss to what extent TRP channels have adhered to their promise as new pharmacological targets in the lower urinary tract (LUT) and to outline the challenges that lie ahead.

  • TRP vanilloid 1 (TRPV1) agonists have proven their efficacy in the treatment of neurogenic detrusor overactivity (DO), albeit at the expense of prolonged adverse effects as pelvic ‘burning’ pain, sensory urgency and haematuria.
  • TRPV1 antagonists have been very successful in preclinical studies to treat pain and DO. However, clinical trials with the first generation TRPV1 antagonists were terminated early due to hyperthermia, a serious, on-target, side-effect.
  • TRP vanilloid 4 (TRPV4), TRP ankyrin 1 (TRPA1) and TRP melastatin 8 (TRPM8) have important sensory functions in the LUT. Antagonists of these channels have shown their potential in pre-clinical studies of LUT dysfunction and are awaiting clinical validation.
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Editorial: TRP channel – a reality that still requires many years of scientific efforts

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Seventeen years have elapsed since the capsaicin receptor was first cloned by Caterina et al. [1] and the excellent review with an unusual provocative title by Deruyver et al. [2] was written. The capsaicin channel, re-named transient receptor potential (TRP) vanilloid receptor subtype 1 (TRPV1), is now commonly referred to as the founding member of the TRP family, as it currently includes 28 related channels, a number difficult to foresee in those early years [3].

TRP channels have been extensively studied in the lower urinary tract (LUT) with the aim of clarifying their role in micturition control and in the generation of LUTS. It is well accepted that TRP receptors have neuronal and non-neuronal expression [3, 4]. TRPV1 is fundamental to bladder hyperactivity and pain associated with LUT inflammation [3], while TRPV4 may participate in the generation of the normal sensation to void [5]. Another group of TRP receptors may even participate in bladder oncogenesis, which seems to be a role of TRPV2 [3]. The main substance of all this information is not a myth; rather it represents a large body of very solid scientific data.

There are certainly still many obscure areas. The distribution of TRP receptors in the bladder is certainly one of them. However, I disagree that a substantial part of available technical and financial resources have been allocated to study this matter. One should not forget that other matters, like the role of many TRP channels for bladder function, remain elusive. Broadly speaking, in my opinion, future key studies should tackle three very relevant but still unclear points. The importance of most TRP channels for bladder function is difficult to predict at the moment [3]. Just as an example, TRPA1 and TRPM8, which are sensitive to cold temperatures, are expressed in the bladder. However, the bladder, as all internal organs, is conserved at very constant physiological temperatures, making it difficult to understand the relevance of cold receptors to its function. Then, we need to find what the endogenous agonists for TRP receptors are in the LUT. Anandamide has been largely explored as an endogenous agonist for TRPV1 in the bladder [6], a fruitful observation as drugs able to manipulate endogenous levels of anandamide are currently being explored in clinical trials. The same holds true for the other members of the TRP family. TRPA1 may respond to infections due to its capacity to react to hydrogen sulphide [3]. But for the large majority of the TRP family endogenous agonists remain unknown. Finally, TRP antagonists that are simultaneously effective and safe must be generated. Most available TRPV1 antagonists, produced to date, although able to control bladder dysfunction in models of cystitis and spinal cord injury [3], cause hyperthermia and have been associated with an enlargement of ischaemic areas of the heart after coronary artery obstruction [3]. TRPV4 antagonists look very promising for controlling frequency but a compound safe for human use is still eagerly awaited [2]. Eventually the combination of antagonists for more than one of these receptors may prove effective at very low doses, so low that they do not generate serious adverse effects [7].

In conclusion, TRP receptors are a reality that still needs an enormous amount of work and dedication before becoming therapeutically useful. And that may take more time than we anticipate at the moment.

 

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Francisco Cruz
Department of Urology, Al. Hernani Monteiro, Porto, Portugal

 

References

 

1 Caterina MJ, Schumacher MA, Tominaga M, Rosen TA, Levine JD, Julius D. The capsaicin receptor: a heat-activated ion channel in the pain pathway. Nature 1997; 389: 816–24

 

2 Deruyver Y, Voets T, De Ridder D, Everaerts W. Transient receptor potential channel modulators as pharmacological treatments for lower urinary tract symptoms: myth or reality? BJU Int 2015; 115: 686–97

 

3 Avelino A, Charrua A, Frias B et al. Transient receptor potential channels in bladder function. Acta Physiol (Oxf) 2013; 207: 110–122

 

4 Birder LA, Kanai AJ, de Groat WC et al. Vanilloid receptor expression suggests a sensory role for urinary bladder epithelial cells. Proc Natl Acad Sci U S A 2001; 98: 13396–401

 

5 Gevaert T, Vriens J, Segal A et al. Deletion of the transient receptor potential cation channel TRPV4 impairs murine bladder voiding. J Clin Invest 2007; 117: 3453–62

 

6 Dinis P, Charrua A, Avelino A et al. Anandamide-evoked activation of vanilloid receptor 1 contributes to the development of bladder hyperreflexia and nociceptive transmission to spinal dorsal horn neurons in cystitis. J Neurosci 2004; 24: 11253–63

 

7 Charrua A, Cruz C, Jansen K, Rozenberg B, Heesakkers J, Cruz F. Co- administration of transient receptor potential vanilloid 4 (TRPV4) and TRPV1 antagonists potentiates the effect of each drug in a rat model of cystitis. BJU Int 2014; [Epub ahead of print] doi: 10.1111/bju.12861

 

Video: TRP channel modulators as pharmacological treatments for LUTS – myth or reality?

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Transient receptor potential channel modulators as pharmacological treatments for lower urinary tract symptoms (LUTS): myth or reality?

Yves Deruyver*‡¶, Thomas Voets†¶, Dirk De Ridder*‡¶and Wouter Everaerts*§¶

 

*Laboratory of Experimental Urology, Department of Development and Regeneration,† Laboratory for Ion Channel Research, Department of Molecular Cell Biology, KU Leuven, ‡University Hospitals Leuven, TRP Research Platform Leuven (TRPLe), Leuven, Belgium, and §Royal Melbourne Hospital, Melbourne, Australia

 

Read the full article

Transient receptor potential (TRP) channels belong to the most intensely pursued drug targets of the last decade. These ion channels are considered promising targets for the treatment of pain, hypersensitivity disorders and lower urinary tract symptoms (LUTS). The aim of the present review is to discuss to what extent TRP channels have adhered to their promise as new pharmacological targets in the lower urinary tract (LUT) and to outline the challenges that lie ahead.

  • TRP vanilloid 1 (TRPV1) agonists have proven their efficacy in the treatment of neurogenic detrusor overactivity (DO), albeit at the expense of prolonged adverse effects as pelvic ‘burning’ pain, sensory urgency and haematuria.
  • TRPV1 antagonists have been very successful in preclinical studies to treat pain and DO. However, clinical trials with the first generation TRPV1 antagonists were terminated early due to hyperthermia, a serious, on-target, side-effect.
  • TRP vanilloid 4 (TRPV4), TRP ankyrin 1 (TRPA1) and TRP melastatin 8 (TRPM8) have important sensory functions in the LUT. Antagonists of these channels have shown their potential in pre-clinical studies of LUT dysfunction and are awaiting clinical validation.
Read more articles of the week

Article of the Week: Using cardiopulmonary reserve to predict complications following radical cystectomy

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Every week the Editor-in-Chief selects the Article of the Week from the current issue of BJUI. The abstract is reproduced below and you can click on the button to read the full article, which is freely available to all readers for at least 30 days from the time of this post.

In addition to the article itself, there is an accompanying editorial written by a prominent member of the urological community. This blog is intended to provoke comment and discussion and we invite you to use the comment tools at the bottom of each post to join the conversation.

If you only have time to read one article this week, it should be this one.

 

Cardiopulmonary Reserve as Determined by Cardiopulmonary Exercise Testing Correlates with Length of Stay and Predicts Complications following Radical Cystectomy

 

Stephen Tolchard, Johanna Angell, Mark Pyke, Simon Lewis, Nicholas Dodds, Alia Darweish, Paul White* and David Gillatt†

 

Departments of Anaesthesia and† Surgery, North Bristol NHS Trust, and *Applied Statistics Group, Department of Mathematics and Statistics, University of the West of England, Bristol, UK

 

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OBJECTIVES

To investigate whether poor preoperative cardiopulmonary reserve and comorbid state dictate high-risk status and can predict complications in patients undergoing radical cystectomy (RC).

PATIENTS AND METHODS

In all, 105 consecutive patients with transitional cell carcinoma (TCC; stage T1–T3) undergoing robot-assisted (38 patients) or open (67) RC in a single UK centre underwent preoperative cardiopulmonary exercise testing (CPET). Prospective primary outcome variables were all-cause complications and postoperative length of stay (LOS). Binary logistic regression analysis identified potential predictive factor(s) and the predictive accuracy of CPET for all-cause complications was examined using receiver operator characteristic (ROC) curve analysis. Correlations analysis employed Spearman’s rank correlation and group comparison, the Mann–Whitney U-test and Fisher’s exact test. Any relationships were confirmed using the Mantel–Haenszel common odds ratio estimate, Kaplan–Meier analysis and the chi-squared test.

RESULTS

The anaerobic threshold (AT) was negatively (r = −206, P = 0.035), and the ventilatory equivalent for carbon dioxide (VE/VCO2) positively (r = 0.324, P = 0.001) correlated with complications and LOS. Logistic regression analysis identified low AT (<11 mL/kg/min), high VE/VC02 (≥33) and hypertension as significant factors, such that, in their presence patients were 5.55-times more likely to have complications at 90 days postoperatively [P = 0.001, 95% confidence interval (CI) 2.2–13.9]. ROC analysis showed a high significance (area under the curve 0.78, 95% CI 0.69–0.87; P < 0.001). In addition, based on CPET criteria >50% of patients presenting for RC had significant heart failure, whereas preoperatively only very few (2%) had this diagnosis. Analysis using the Mann–Whitney test showed that a VE/VCO2 ≥33 was the most significant determinant of LOS (P = 0.004). Kaplan–Meier analysis showed that patients in this group had an additional median LOS of 4 days (P = 0.008). Finally, patients with an American Society of Anesthesiologists grade of 3 (ASA 3) and those on long-term β-blocker therapy were found to be at particular risk of myocardial infarction (MI) and death after RC with odds ratios of 4.0 (95% CI 1.05–15.2; P = 0.042) and 6.3 (95% CI 1.60–24.8; P = 0.008).

CONCLUSION

Patients with poor cardiopulmonary reserve and hypertension are at higher risk of postoperative complications and have increased LOS after RC. Heart failure is known to be a significant determinant of perioperative death and is significantly under diagnosed in this patient group.

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Editorial: Cardiopulmonary exercise testing: fortune-teller or guardian angel?

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In this month’s issue of BJUI, Tolchard et al. [1] describe their experience with the use of cardiopulmonary exercise testing (CPET) in patients undergoing radical cystectomy. In particular, they assess the value of cardiopulmonary reserve in predicting complications and the length of stay in hospital after surgery.

The origin of CPET is in non-surgical specialties for the further investigation of patients with cardiac failure or unexplained breathlessness [2], but it subsequently gained utility in surgical fields, including the preoperative assessment of patients undergoing cardiac surgery [3].

In more recent times, it has been increasingly adopted within ‘high-risk’ preoperative assessment clinics for those patients undergoing a wide range of major elective, non-cardiac surgery; however, this enthusiastic uptake has often preceded more formal validation of the test’s ability to perform reliably in these new patient groups and their associated surgical procedures. The Bristol group [1] has therefore prospectively studied the role of CPET in 105 patients undergoing either robot-assisted or open radical cystectomy for TCC, using all-cause complications and length of stay as the primary outcome variables.

The researchers found that anaerobic threshold (AT), ventilatory equivalent for carbon dioxide (VE/VCO2) and hypertension were independent predictors of postoperative complications. Using the criteria chosen by Older et al. [4] of an AT ≤ 11 mL/kg/min and or VE/VECO2 ≥ 33, it was possible to define a high- and low-risk group. The high-risk group were 5.5 times more likely to experience a complication at 90 days compared with the low-risk group and, notably, all deaths and myocardial infarctions occurred in the high-risk group. As expected, they found that complications prolonged length of stay. Additionally, falling AT and or rising VE/VECO2 also correlated with increasing length of stay. Their study therefore suggests that CPET may have a role in the preoperative risk stratification of patients undergoing radical cystectomy by an open or robot-assisted approach.

The authors acknowledge that the cohort size is small and from a single institution, thereby necessitating further validation work across multiple centres, as well as subgroup analysis of differing surgical approaches. Interestingly, their study excluded patients who had received neoadjuvant chemotherapy; for many UK cancer centres, this would exclude ∼70% of patients undergoing radical cystectomy. It would clearly be important in future studies to understand how CPET metrics perform in this wider cohort, where anaemia and impaired performance status are known to be more common.

On the assumption that further studies may validate the use of CPET as a preoperative risk-stratifying tool, the pertinent question is how do we translate this research finding into patient benefit? Interventions such as preoperative patient optimization, pre-habilitation exercise regimes or the planned escalation of postoperative care may confer benefits but, as yet, we do not know if they attenuate the increased risk of complications or the prolonged inpatient stay.

As further evaluation of CPET takes place, we should remain cautious about its use as a ‘rule-out’ investigation in those patients otherwise considered eligible for radical surgical treatment. To date, there have been no formal evaluations of patients’ quality of life or end-of-life care in ‘non-operated’ cases. Poor local control of pelvic malignancy remains one of the most challenging aspects of care for uro-oncologists and, at times, it may even outweigh the impact of postoperative surgical complications. Due consideration must be given to this aspect when advising individual patients about the predicted risks and benefits of therapeutic treatment options. The decision to operate should clearly be informed by the preoperative assessment, but it is imperative that it continues to involve the patient’s wider multidisciplinary team, whose responsibility it will be to provide lifelong care.

In conclusion, CPET offers an interesting opportunity to identify those patients at greatest risk of adverse outcomes after radical cystectomy; however, the full benefits will not be realized if it is simply the ‘bearer of bad news’. The key to its success will be the identification of modifiable behaviours, by both the patient and the clinical team, that lead to improved patient-related outcomes. These outcomes should not be restricted to overall or cancer-specific survival but also measures of return to good health and prior performance status. Such longer-term outcome data may then help us to more accurately delineate the point at which the risks of a surgical treatment can be confidently predicted to outweigh the alternative of non-operative care for individual patients.

Read the full article
John S. McGrath
Royal Devon and Exeter NHS Trust, Exeter, UK

 

References

 

1 Tolchard S, Angell J, Pyke M et al. Cardiopulmonary reserve as determined by cardiopulmonary exercise testing correlates with length of stay and predicts complications following radical cystectomy. BJU Int 2014; [Epub ahead of print]. doi: 10.1111/bju.12895

 

2 Szlachcic J, Massie BM, Kramer BL, Topic N, Tubau J. Correlates and prognostic implication of exercise capacity in chronic congestive heart failure. Am J Cardiol 1985; 55: 1037–42

 

3 Mancini DM, Eisen H, Kussmaul W, Mull R, Edmunds LH Jr, Wilson JR. Value of peak exercise oxygen consumption for optimal timing of cardiac transplantation in ambulatory patients with heart failure. Circulation 1991;83: 778–86

 

4 Older P, Hall A, Hader R. Cardiopulmonary exercise testing as a screening test for perioperative management of major surgery in the elderly. Chest 1999; 116: 355–62

 

Article of the Week: 3D percutaneous navigation, integrating position-tracking with a tablet display

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Every week the Editor-in-Chief selects the Article of the Week from the current issue of BJUI. The abstract is reproduced below and you can click on the button to read the full article, which is freely available to all readers for at least 30 days from the time of this post.

In addition to the article itself, there is an accompanying editorial written by a prominent member of the urological community. This blog is intended to provoke comment and discussion and we invite you to use the comment tools at the bottom of each post to join the conversation.

Finally, the third post under the Article of the Week heading on the homepage will consist of additional material or media. This week we feature a video from Dr. Osamu Ukimura, discussing his paper. 

If you only have time to read one article this week, it should be this one.

Three-dimensional navigation system integrating position-tracking technology with a movable tablet display for percutaneous targeting

Arnaud Marien, Andre Castro de Luis Abreu, Mihir Desai, Raed A. Azhar, Sameer Chopra, Sunao Shoji, Toru Matsugasumi, Masahiko Nakamoto, Inderbir S. Gill and Osamu Ukimura

 

USC Institute of Urology, Center for Focal Therapy of Prostate and Kidney Cancer, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA

 

Read the full article

 

OBJECTIVES

To assess the feasibility of a novel percutaneous navigation system (Translucent Medical, Inc., Santa Cruz, CA, USA) that integrates position-tracking technology with a movable tablet display.

MATERIALS AND METHODS

A total of 18 fiducial markers, which served as the target centres for the virtual tumours (target fiducials), were implanted in the prostate and kidney of a fresh cadaver, and preoperative computed tomography (CT) was performed to allow three-dimensional model reconstruction of the surgical regions, which were registered on the body intra-operatively. The position of the movable tablet’s display could be selected to obtain the best recognition of the interior anatomy. The system was used to navigate the puncture needle (with position-tracking sensor attached) using a colour-coded, predictive puncture-line. When the operator punctured the target fiducial, another fiducial, serving as the centre of the ablative treatment (treatment fiducial), was placed. Postoperative CT was performed to assess the digitized distance (representing the real distance) between the target and treatment fiducials to evaluate the accuracy of the procedure.

RESULTS

The movable tablet display, with position-tracking sensor attached, enabled the surgeon to visualize the three-dimensional anatomy of the internal organs with the help of an overlaid puncture line for the puncture needle, which also had a position-tracking sensor attached. The mean (virtual) distance from the needle tip to the target (calculated using the computer workstation), was 2.5 mm. In an analysis of each digitalized axial component, the errors were significantly greater along the z-axis (P < 0.01), suggesting that the errors were caused by organ shift or deformation.

CONCLUSION

This virtual navigation system, integrating a position-tracking sensor with a movable tablet display, is a promising advancement for facilitating percutaneous interventions. The movable display over the patient shows a preoperative three-dimensional image that is aligned to the patient. Moving the display moves the image, creating the feeling of looking through a window into the patient, resulting in instant perception and a direct, intuitive connection between the physician and the anatomy.

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Editorial: A 3D window into the body?

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If real-time tracking is accurate enough to tell you that Roger Federer’s serve was on the line or that David Beckham’s free kick was indeed over the goal line, then surely tracking systems could help us guide needles and wires into different parts of the body? In this month’s BJUI, Marien et al. give us an insight into the future of access for percutaneous procedures [1]. Currently, percutaneous access to the body for biopsy, renal access or treatment of malignancy is usually based on two-dimensional imaging, with the expertise of the operator compensating for the lack of real-time three-dimensional (3D) visualization of the surgical field. In this paper, the authors hypothesized that integrating virtual reality visualization with real-time position tracking of the needle/instrument would improve navigation. This improvement remains unproven and the study is a first step on that road.

The authors assess the feasibility of a novel method of percutaneous access (TranslucentTM Medical Inc.) using a freely movable tablet display to help guide the percutaneous puncture to its target (see Fig. 1). The success of such a system would rely on a high degree of accuracy and the authors set out to test this in a cadaveric model. Fiducial markers were placed in the kidneys and prostates of cadavers to mimic tumours. A CT scan was then performed to allow 3D model reconstruction. An electromagnetic field was generated around the body and magnetic sensors (fixed to the skin and in the urethral catheter) were used for localization. The software then allows real-time demonstration of the needle trajectory with a predicted line beyond the needle tip overlaid on the 3D model. The authors were able to quickly reach the target (mean time 43 s) with apparent good accuracy, which was calculated to be within 2.5 mm; however, further fiducial markers were deployed at the centre of the target to allow the accurate measurement of accuracy. The distance between the ‘target’ fiducial and the ‘treatment’ fiducial was 16.6 mm in the prostate and 12.0 mm in the kidney. This difference was probably attributable to either movement of the organ or deformation of it from the needle puncture itself. These errors were predominantly in the z-axis (i.e. depth), suggesting that they were caused by movement and deformation by the needle itself, which therefore poses the challenge of how the errors might be reduced, especially when a living human model may have more compliant tissues and of course be moving with respiration.

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Figure 1. Tablet screen displaying real-time ‘three-dimensional window into the body’ with real and projected trajectory of needle

The present paper by Marien et al. is not the first report of using tracking for percutaneous access in urology. Using different technology, Rassweiler et al. [2] reported on the percutaneous puncture of the kidney for nephrolithotomy using an iPad with surface skin markers, which were visualized by the rear-facing camera of the iPad, and this information was processed to calculate the location of the tissues beneath based on a preoperative CT. This system, and I suspect all others, will rely on a CT being performed in the exact position of the surgery, which is another limiting step until this can be performed at the same time as the surgery.

There are of course concerns regarding use of this technology. The accuracy was limited when analysing the actual position of the ‘treatment’ fiducial because of movement of the tissues. This is likely to be worse in living tissue. There was no respiratory movement which would probably make accurate tracking difficult, although placement of markers to allow movement tracking may help overcome this. Rodrigues et al. [3] reported high accuracy of percutaneous nephrolithotomy puncture after deployment of an electromagnetic sensor in the target calyx with ureterorenoscopy in a porcine model but without a 3D model.

My major concern is that of false reassurance. A nice image is portrayed on the screen which is believed by the surgeon, while in fact there is a significant mismatch caused by patient/tissue movement, either since the preoperative planning CT scan or intra-operatively. The falsely reassured surgeon then inadvertently damages surrounding organs.

It is clear that this technology is work in progress, but it does offer promise that real-time tracking of a percutaneous needle is possible, with accurate representation on a 3D model reconstruction helping to guide the surgeon to the target.

Read the full article
Matthew Bultitude

 

Department of Urology, Guy’s and St. Thomas’ Hospital, London, UK

 

 

References

 

1 Marien A, De Castro Abreu AL, Desai M et al. Three-dimensional navigation system integrating position-tracking technology with movable tablet display for percutaneous targeting. BJU Int 2015; 115: 659–65

 

2 Rassweiler JJ, Muller M, Fangerau M et al. iPad-assisted percutaneous access to the kidney using marker-based navigation: initial clinical experience. Eur Urol 2012; 61: 628–31

 

3 Rodrigues PL, Vilaca JL, Oliveira C et al. Collecting system percutaneous access using real-time tracking sensors: first pig model in vivo experience. J Urol 2013; 190: 1932–7

 

Video: Percutaneous targeting using 3D navigation that integrates position-tracking technology with a tablet display

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Three-dimensional navigation system integrating position-tracking technology with a movable tablet display for percutaneous targeting

Arnaud Marien, Andre Castro de Luis Abreu, Mihir Desai, Raed A. Azhar, Sameer Chopra, Sunao Shoji, Toru Matsugasumi, Masahiko Nakamoto, Inderbir S. Gill and Osamu Ukimura

 

USC Institute of Urology, Center for Focal Therapy of Prostate and Kidney Cancer, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA

 

Read the full article
OBJECTIVES

To assess the feasibility of a novel percutaneous navigation system (Translucent Medical, Inc., Santa Cruz, CA, USA) that integrates position-tracking technology with a movable tablet display.

MATERIALS AND METHODS

A total of 18 fiducial markers, which served as the target centres for the virtual tumours (target fiducials), were implanted in the prostate and kidney of a fresh cadaver, and preoperative computed tomography (CT) was performed to allow three-dimensional model reconstruction of the surgical regions, which were registered on the body intra-operatively. The position of the movable tablet’s display could be selected to obtain the best recognition of the interior anatomy. The system was used to navigate the puncture needle (with position-tracking sensor attached) using a colour-coded, predictive puncture-line. When the operator punctured the target fiducial, another fiducial, serving as the centre of the ablative treatment (treatment fiducial), was placed. Postoperative CT was performed to assess the digitized distance (representing the real distance) between the target and treatment fiducials to evaluate the accuracy of the procedure.

RESULTS

The movable tablet display, with position-tracking sensor attached, enabled the surgeon to visualize the three-dimensional anatomy of the internal organs with the help of an overlaid puncture line for the puncture needle, which also had a position-tracking sensor attached. The mean (virtual) distance from the needle tip to the target (calculated using the computer workstation), was 2.5 mm. In an analysis of each digitalized axial component, the errors were significantly greater along the z-axis (P < 0.01), suggesting that the errors were caused by organ shift or deformation.

CONCLUSION

This virtual navigation system, integrating a position-tracking sensor with a movable tablet display, is a promising advancement for facilitating percutaneous interventions. The movable display over the patient shows a preoperative three-dimensional image that is aligned to the patient. Moving the display moves the image, creating the feeling of looking through a window into the patient, resulting in instant perception and a direct, intuitive connection between the physician and the anatomy.

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Article of the Week: With a previous negative prostate biopsy and a suspicious lesion on MRI, is a 12-core biopsy still necessary in addition to a targeted biopsy?

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Every week the Editor-in-Chief selects the Article of the Week from the current issue of BJUI. The abstract is reproduced below and you can click on the button to read the full article, which is freely available to all readers for at least 30 days from the time of this post.

In addition to the article itself, there is an accompanying editorial written by a prominent member of the urological community. This blog is intended to provoke comment and discussion and we invite you to use the comment tools at the bottom of each post to join the conversation.

Finally, the third post under the Article of the Week heading on the homepage will consist of additional material or media. This week we feature a video from Dr. Art R. Rastinehad , discussing his paper. 

If you only have time to read one article this week, it should be this one.

In patients with a previous negative prostate biopsy and a suspicious lesion on magnetic resonance imaging, is a 12-core biopsy still necessary in addition to a targeted biopsy?

Simpa S. Salami*, Eran Ben-Levi†, Oksana Yaskiv‡, Laura Ryniker*, Baris Turkbey§, Louis R. Kavoussi*, Robert Villani† and Ardeshir R. Rastinehad*†

 

*The Arthur Smith Institute for Urology, †Department of Diagnostic and Interventional Radiology, and ‡Department of Pathology, Hofstra North Shore-LIJ School of Medicine, New Hyde Park, NY, and § Molecular Imaging Program, National Institutes of Health, Bethesda, MD, USA

 

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OBJECTIVES

To evaluate the performance of multiparametric magnetic resonance imaging (mpMRI) in predicting prostate cancer on repeat biopsy; and to compare the cancer detection rates (CDRs) of MRI/transrectal ultrasonography (TRUS) fusion-guided biopsy with standard 12-core biopsy in men with at least one previous negative biopsy.

PATIENTS AND METHODS

We prospectively enrolled men with elevated or rising PSA levels and/or abnormal digital rectal examination into our MRI/TRUS fusion-guided prostate biopsy trial. Participants underwent a 3 T mpMRI with an endorectal coil. Three radiologists graded all suspicious lesions on a 5-point Likert scale. MRI/TRUS fusion-guided biopsies of suspicious prostate lesions and standard TRUS-guided 12-core biopsies were performed. Analysis of 140 eligible men with at least one previous negative biopsy was performed. We calculated CDRs and estimated area under the receiver operating characteristic curves (AUCs) of mpMRI in predicting any cancer and clinically significant prostate cancer.

RESULTS

The overall CDR was 65.0% (91/140). Higher level of suspicion on mpMRI was significantly associated with prostate cancer detection (P < 0.001) with an AUC of 0.744 compared with 0.653 and 0.680 for PSA level and PSA density, respectively. The CDRs of MRI/TRUS fusion-guided and standard 12-core biopsy were 52.1% (73/140) and 48.6% (68/140), respectively (P = 0.435). However, fusion biopsy was more likely to detect clinically significant prostate cancer when compared with the 12-core biopsy (47.9% vs 30.7%; P < 0.001). Of the cancers missed by 12-core biopsy, 20.9% (19/91) were clinically significant. Most cancers missed by 12-core biopsy (69.6%) were located in the anterior fibromuscular stroma and transition zone. Using a fusion-biopsy-only approach in men with an MRI suspicion score of ≥4 would have missed only 3.5% of clinically significant prostate cancers.

CONCLUSIONS

Using mpMRI and subsequent MRI/TRUS fusion-guided biopsy platform may improve detection of clinically significant prostate cancer in men with previous negative biopsies. Addition of a 12-core biopsy may be needed to avoid missing some clinically significant prostate cancers.

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