How do you define "low-volume" intermediate risk prostate cancer that is appropriate for brachytherapy alone?

For prostate cancer the use of PSA, T-stage, and Gleason score have been used to create multiple different risk stratification schemes. That of @Dr. First Last, the NCCN, and the AJCC are all very similar. In addition, other methods such as the Memorial Sloan Kettering nomograms and the CAPRA score have added additional features (usually the difference between primary and secondary Gleason grade as well as the use of percentage of biopsy cores involved). Although not assessed in randomized trials the AJCC also now recognizes a distinction between Gleason 3+4 vs. 4+3 in their intermediate risk staging.

For prostate brachytherapy a number of publications have suggested that "low intermediate risk" or "low volume intermediate risk" are appropri...

@Dr. First Last has summed up the most relevant empiric evidence available to date. This provides the assurance that favorable-interm risk prostate cancers with good urinary function are generally good candidates for brachytherapy monotherapy. Yet, with regards to patients with more aggressive GS 7 disease, he has left out considerations that can be made when patients have access to a high-quality brachytherapy program.

Consider a scenario where >98% of prostate is actually covered by the 100% IDL. Conventional post-implant CT based dosimetry can estimate whether this has happened. But, it really takes a post-implant MRI to know for sure if any cold spots were left behind at the base or apex (we're seeing V100 and d90 differences of over 10...

I would just say that probably any increase in risk factors increases risk. Perhaps even "secondary" gleason score, meaning if you had only a small core of G3+4 but the rest G3+3 your secondary score is 6 or if G4+3 but you had another G3+4 then your secondary is 3+4.

Also number of cores + is a moving target. CAPRA uses 1/3 vs D'Amico uses 1/2 of cores +.

MRI is not unreasonable to use to risk stratifying, though this is without prospective data. Low volume, lower grade prostate cancer should either be not visible on a MRI or minimally visible. If the MRI is not commensurate with low volume disease then de-escalation of therapy or surveillance is likely not appropriate.

If you are =/< 1/3 of cores +, Gleason 3+4, minimal disease on MRI, PS...