PSMA‐PET‐guided dose‐escalated volumetric arc therapy for newly diagnosed lymph node‐positive prostate cancer: 5 Year outcomes following the FROGG and EviQ node‐positive guidelines

Abstract

Introduction The Royal Australian and New Zealand College of Radiologists (RANZCR) Faculty of Radiation Oncology Genitourinary Group (FROGG) guidelines and online EviQ protocols incorporate prostate‐specific membrane antigen (PSMA) positron emission tomography (PET)‐guided dose‐escalated intensity‐modulated radiation therapy (DE‐IMRT) for newly diagnosed lymph node (LN) positive prostate cancer. We evaluated late toxicity and efficacy outcomes following the FROGG and EviQ approach. Methods Patients with LN‐positive‐only metastases on PSMA‐PET imaging were offered curative therapy with 3 months neoadjuvant androgen deprivation therapy (ADT) followed by DE‐IMRT and 3 years adjuvant ADT. IMRT was delivered via volumetric arc therapy (VMAT). We aimed to deliver 81 Gy in 45 fractions (Fx) to the prostate and PET‐positive LNs, and 60 Gy in 45 Fx to elective pelvic nodes, contoured using the PIVOTAL guidelines. Results Forty‐five patients were included. The median number of PET‐positive nodes boosted was 2 (range 1–6) and median boost volume 1.16 cc (range 0.15–4.14). Seventeen (38%) patients had PET‐positive nodes outside of PIVOTAL contouring guidelines. With 60 months median follow‐up, disease‐free, metastasis‐free, prostate cancer‐specific and overall survival were 88.1%, 95.3%, 100% and 91.5%. There were no in‐field nodal failures. Late grade 1, 2 and 3 gastrointestinal toxicities occurred in 4%, 2% and 0% of patients, and genitourinary toxicity in 18%, 18% and 4%. Lower limb grade 2 lymphoedema occurred in three patients (7%). Conclusion Outcomes following FROGG guidelines and EviQ are promising, with high long‐term disease control and low toxicity. Contouring guidelines require modification due to the high rate of PET‐positive nodes demonstrated beyond recommended coverage.