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Introduction: The Australian Faculty of Radiation Oncology Genitourinary Group (FROGG) developed prostate bed clinical target volume (CTV) contouring guidelines which were subsequently used to develop the National EviQ guidelines for adjuvant and salvage post‐prostatectomy radiotherapy (PPRT). These guidelines were based mainly upon consensus agreement. With the advent of prostate‐specific membrane antigen (PSMA) positron emission tomography (PET), sites of recurrence can now be detected with low prostate‐specific antigen (PSA) levels following radical prostatectomy. We evaluated sites of recurrence in patients treated with FROGG/EviQ CTVs to inform upcoming modifications of these guidelines. Methods: At our institution, we use the FROGG/EviQ guidelines for PPRT. From 2015, patients with PSA failure following PPRT have been re‐staged using PSMA PET imaging. We identified patients with PET‐avid local, nodal, and distant recurrences, fusing them with original treatment plans to determine whether recurrences were within or outside the prostate bed CTV. Regional nodal failures were reviewed to determine if they were within current elective node contouring guidelines. Results: Ninety‐four patients had positive PSMA PET following PPRT. Nine (9.6%) recurrences were local, seven being local‐only. One local recurrence (1.1%) was just superior to the contoured prostate bed CTV, located within the vas deferens. Seventy‐three (77.7%) patients had a component of node failure, with 56 (59.6%) having node‐only failure. Sites of nodal relapses were covered by standard contouring guidelines 60.3% of the time. Conclusion: The low recurrence rate outside of current prostate bed CTV contouring guidelines is consistent with other studies using contemporary contouring, and validates the efficacy of the current FROGG/EviQ prostate bed CTV definition. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]