3363 - Outcomes after Pelvic Radiotherapy and Androgen Deprivation Therapy for Pathologic Node-Positive Prostate Cancer in the PSMA PET Era
Presenter(s)
S. Romano1, S. Sadeghi2, A. Lim3, M. Aron4, J. Pinski2, A. Abreu4, A. D'Souza5, D. I. Quinn2, V. Tulpule2, H. Djaladat4, A. Lebastchi4, I. Gill4, S. Daneshmand4, A. Schuckman4, M. Desai4, M. Nguyen4, M. L. Tao6, E. R. Zhang-Velten6, B. Nanton1, and L. Lukas6; 1Keck School of Medicine, University of Southern California, Los Angeles, CA, 2Division of Medical Oncology, Keck School of Medicine, University of Southern California, Los Angeles, CA, 3Department of Radiation Oncology, Keck School of Medicine, University of Southern California, Los Angeles, CA, 4USC Institute of Urology, Keck School of Medicine, University of Southern California, Los Angeles, CA, 5Department of Hematology and Oncology, LAC+USC Medical Center, Los Angeles, CA, 6Department of Radiation Oncology, University of Southern California Keck School of Medicine, Los Angeles, CA
Purpose/Objective(s): The management of pathologic node-positive (pN1) prostate cancer following radical prostatectomy (RP) is controversial. Randomized postoperative radiotherapy trials largely exclude pN1 patients, and it remains unclear whether low-volume pN1 disease behaves more like high-risk node-negative disease or represents early systemic spread. We report oncologic and toxicity outcomes in a uniformly treated pN1 cohort managed with pelvic radiotherapy (RT) and androgen deprivation therapy (ADT) in the PSMA PET era.
Materials/Methods: We retrospectively reviewed 103 pN1 patients treated with adjuvant or early salvage RT between 2019–2026. Median age at RP was 67 years. Adverse features were common: Grade Group 4–5 (66%), pT3 disease (96%), extracapsular extension (93%), seminal vesicle invasion (70%), and positive margins (55%). Median lymph nodes removed was 20, with a median of 1 positive node (range 1–8). Persistent postoperative PSA was present in 65% (median 0.14 ng/mL). PSMA PET was obtained pre-RT in 30%. Pelvic nodal RT was delivered in 99% using a sequential boost approach (45 Gy pelvis followed by prostate fossa boost to 64–68 Gy) or a simultaneous integrated boost (SIB) technique to 62.5 Gy. 92% received ADT (8% = 6 months) and 5% also received an ARPI.
Results: At a median follow-up of 4.7 years post RP and following completion of radiation, 34% developed a detectable PSA and 21% developed metastatic disease. Among those with metastases, 17% were oligometastatic and 4% had diffuse disease. Sites of distant failure included nodal (10%) and osseous (16%) metastases. Visceral metastasis developed in one patient with neuroendocrine differentiation. Isolated prostate fossa recurrence was rare (1%). Pelvic nodal recurrence occurred in 4%, including the one patient treated with prostate fossa–only RT, supporting high regional control. Castration resistant disease developed in 8%. Two patients (2%) died; 4-year overall survival was 97.8% and metastasis-free survival of 87%.
Acute GU toxicity was grade 1–2 in 86% and acute GI toxicity was grade 1–2 in 35%. There was no acute grade =3 toxicity. Late GU toxicity was grade 1–2 in 50% and grade =3 in 17%. Late GI toxicity was grade 1–2 in 6% and grade =3 in 2%.
Conclusion: In this PSMA PET–era cohort of predominantly low-volume pN1 patients treated with pelvic RT (sequential or SIB) and long-course ADT, durable local-regional control was achieved with 87% metastasis-free survival at 4 years. However, approximately one in eight patients developed metastatic progression by 4 years despite aggressive multimodality therapy, supporting the concept that while many low-volume pN1 patients behave similarly to high-risk node-negative disease, a clinically meaningful subset demonstrates early systemic biology. These findings provide modern benchmark outcomes and inform ongoing efforts toward improved risk stratification and systemic intensification in pN1 prostate cancer.