In 2013, Zumsteg et al. proposed a refinement in the NCCN "intermediate risk" classification into two subcategories, "favorable intermediate-risk (FIR)" and "unfavorable intermediate-risk (UIR)." Based on retrospective studies with short follow-up, they discerned that the two subgroups had divergent prognoses when treated with external beam radiation and adjuvant androgen deprivation therapy (ADT). Since then, others have found that it is also a useful division for deciding whether brachy boost therapy is beneficial (see this link), or whether it is beneficial to add ADT to brachytherapy (see this link). Some FIR patients may be suitable candidates for active surveillance.
It has also been found to be a useful division in terms of prognosis following surgery, brachytherapy, and SBRT (see this link). Some clinical trials use the definition to distinguish "favorable risk" (low risk or FIR) from "unfavorable risk" (UIR or high risk). Since 2016, NCCN has incorporated the distinction in its risk stratification system.
The NCCN definitions are as follows:
Now, it has been found to be a useful distinction in an unplanned secondary analysis of a randomized clinical trial, with 17.8 years of median follow-up. Such a long follow-up is unusual for a clinical trial and gives us the ability to see significant numbers of mortality and metastases even in intermediate-risk patients. The trial, RTOG 9408, was originally conducted among 1,068 intermediate-risk patients who received 66.6 Gy to the prostate (low by today's standards) and 46.8 Gy to the pelvic lymphatics. Half the patients received 4 months of adjuvant ADT, and half received none. They lacked biopsy core information on 16%, who are excluded from their analysis. Zumsteg et al. found that adding 4 months of ADT:
- more than doubled 15-year metastasis-free survival and prostate cancer-specific survival among UIR patients. Mean overall survival was 0.7 years longer with ADT.
- had no statistically significant effect on 15-year metastasis-free survival, prostate cancer-specific survival, or overall survival among FIR patients
- it took about 6 years for the differences to start to be noticeable.
Given all the retrospective studies we've seen before that all point to FIR vs UIR as a useful and significant distinction, this is not surprising. It did take a lot of work to review pathology reports on almost a thousand patients, and the authors are to be commended for doing so. If it spares some FIR men from being overtreated, it was a worthwhile effort.