Editorial: Current Gleason score 3 + 4 = 7: has it lost its significance compared with its historical counterpart?
Berg et al. [1] report that patients classified as Gleason score 7 (3 + 4) according to the revised grading system published in 2005 are to some extent similar to patients with pre-2005 Gleason score 6, at least in terms of risk of biochemical recurrence. The logical but not necessarily correct conclusion is that current patients with Gleason score 7 on biopsy are appropriate candidates for active surveillance.
What must be kept in mind is that, using the post-2005 revised grading system, approximately 25% of men with Gleason score 3 + 4 = 7 on biopsy have either 3 + 4 = 7 with tertiary pattern 5 or >4 + 3 = 7 in the corresponding radical prostatectomy [1]. With the exception of men with a limited life expectancy, these men need definitive therapy for their potentially life-threatening cancer. Numerous studies have shown that extended biopsies, whether they are >10- or 12-core, are associated with less upgrading than sextant biopsies [2]. In the report by Berg et al. [1], the median number of cores sampled before 2005 was 6 with an interquartile range (IQR) of 6–6 compared with a median (IQR) of 10 (10–12) cores after 2005. Consequently, in their cohorts, the pre-2005 group of men with Gleason score 3 + 3 = 6 were more likely to have unsampled higher grade cancer and a correspondingly worse prognosis more closely approximating post-2005 better-sampled Gleason score 3 + 4 = 7 cancers.
Berg et al. [1] further claim that the prognostic and clinical value of Gleason score 7 has been weakened since the 2005 modifications. In fact, the revised grading system more accurately reflects prostate cancer biology than the pre-2005 Gleason system. The major consequence of the modification, as Berg et al. [3] illustrate, has been the better prognosis associated with post-2005 Gleason score 6 cancer because patterns associated with more aggressive behaviour have been shifted to Gleason score 7. Historically, a diagnosis of Gleason score 6 cancer, even at radical prostatectomy, was not as predictive of ‘good’ behaviour, and had a higher rate of progression with some men even dying from prostate cancer [4]. Currently, Gleason score 6 cancer at radical prostatectomy has a 96% cure rate at 5 years, even including cases with extraprostatic extension and positive margins [3]. Several studies have shown that post-2005 pure Gleason score 6 cancers at radical prostatectomy are incapable of metastasizing to lymph nodes [4]. Berg et al. are correct, however, that men with a post-2005 grade of Gleason Score 3 + 4 = 7 have a better prognosis than those graded prior to 2005. As a consequence, it has been recommended that pathologists should record the percent pattern 4 in cases with Gleason score 7 on biopsy for men being considered for active surveillance [5]. For the appropriate patient, depending on age, comorbidity, extent of cancer, MRI findings, patient desire, etc., could be a candidate for active surveillance with Gleason score 3 + 4 = 7 if the pattern 4 is limited. Currently, this information is not transparent in most pathology reports.
A new grading system, first proposed in BJUI by this author, and verified in a large multi-institutional study, resulted in a simplified five-grade group system that more accurately reflects the biology of prostate cancer than the pre-2005 grading system [3, 6]. Men with Gleason score 6 cancers need to be reassured that their cancer is the lowest grade that is currently assigned, despite Gleason scores ranging from 2 to 10. In addition, I have talked to some patients with Gleason score 3 + 4 = 7 who think that they are going to die in the near future because their score of 7 was closer to highest grade of 10 than the lowest grade of 2. With the new grading system, patients can be reassured that they have a Grade group 1 (3 + 3 = 6) out of 5, which is the lowest grade, or a Grade group 2 (Gleason score 3 + 4 = 7) out of 5, which is still a relatively low grade.
