When it is not obvious that there are cancerous pelvic lymph nodes, it may nonetheless improve outcomes to treat the whole pelvic area with radiation. The decision of whether to treat it or not is often made based on the "Roach formula":
% pelvic LN risk = PSA * 2/3 + ((Gleason score – 6) * 10) ≥ 15%
Based on that formula, all men with Gleason scores of 8-10 should have whole pelvic radiation (WPRT). But even men newly diagnosed with Gleason 9 or 10 may not have any metastases in pelvic lymph nodes. WPRT may be over-treatment for some. This article discusses the evidence that patients and their radiation oncologists should consider.