In the 1960s, a pathologist named Donald Gleason and his colleagues at the Minneapolis VA Hospital developed a numerical system for ranking prostate cancer (PCa) aggressiveness on a scale from 1 to 5. The Gleason grade (or Gleason score) system named after him have been in use ever since as a way to understand how aggressive a patient’s PCa disease is, and planning treatment accordingly.
Now, 17 experts from Johns Hopkins, Memorial Sloan Kettering, U Pittsburgh, Cleveland Clinic, and Sweden’s Karolinska Institute propose a simplified 5-point system.[i] Their thinking is based on analyzing the records of more than 26,000 patients (20,845 had prostatectomy, 5501 had radiation).
When is a 7 not a 7?
The alternate system would have the advantage of simplicity. Today’s Gleason grade is not a true 5-point scale because it involves summing up two values. Which number comes first is based on the largest per cent of PCa seen in each positive needle sample. Thus, Gleason 3 + 4 = 7 is different from Gleason 4 + 3 = 7; the second sum is more dangerous because there is more Gleason 4 than 3. Even though the Gleason system is based on numbers 1 through 5, the actual scale used is this:
3 + 3 = 6 (lowest grade PCa)
3 + 4 = 7
4 + 3 = 7
4 + 4 = 8
4 + 5 = 9
5 + 4 = 9
5 + 5 = 10
It’s really a 7-point scale. The authors state, “The lowest score, assigned 6, may be misunderstood as a cancer in the middle of the grading scale, and 3+4=7 and 4+3=7 are often considered the same prognostic group.” (Note that any sum less than 6 is not used for planning treatment.) Confusing, right?
Why would a new system be better?
A true 5-point scale can offer the smallest number of grades with “more accurate grade stratification.” This simplifies treatment planning. According to the authors, if the lowest grade is 1 instead of 6 (3 + 3), the current tendency to overtreat low-risk PCa can be greatly reduced.
I like the 5-point scale, an idea similar to the PI-RADS scoring system radiologists use to interpret multiparametric MRI prostate scans. (See my blog at https://sperlingprostatecenter.com/pi-rads-score/ to learn more.) Given the tendency of the medical profession to change slowly and cautiously, I don’t foresee rapid wide-spread adoption of a new system. However, the authoritative institutions and experts behind this study should help their proposal gain the consideration it well deserves. I expect that there will be quite a buzz about it at next year’s annual American Urological Association meeting.
[i] Epstein JI, Zelefsky MJ, Sjoberg DD, Nelson JB et al. A Contemporary Prostate Cancer Grading System: A Validated Alternative to the Gleason Score. Eur Urol. 2015 Jul 9. pii: S0302-2838(15)00557-6. doi: 10.1016/j.eururo.2015.06.046. [Epub ahead of print]