Oligorecurrent Nodal Prostate Cancer: Long-term Results of an Elective Nodal Irradiation Approach.

Objectives: The objective of this study was to report long-term results of elective nodal radiotherapy (ENRT) in prostate cancer (PCa) patients with oligorecurrent nodal disease after primary treatment. Methods: Data of 53 oligorecurrent PCa patients (N1 and/or M1a) with <= 5 nodal metastases (n=108) treated with ENRT combined with androgen deprivation therapy (ADT) between 2004 and 2016 were retrospectively reviewed. Median prostate-specific antigen (PSA) and PSA doubling time (DT) were 3.4 ng/mL and 5 months, respectively. At restaging, 45% of the patients presented single nodal metastases, mainly located in the pelvis (n=38). All patients underwent ENRT between 45 and 50.4 Gy with a boost on positive nodes (median 64.4 Gy; 54 to 69 Gy) using mainly VMAT (n=24) or IMRT (n=21) techniques. Concomitant ADT was administered to all patients for a median time of 6 months. Results: After a median follow-up after ENRT of 44 months (range, 2 to 133), the 5-year biochemical disease-free and distant progression-free survival (DPFS) rates were 43% and 58%, respectively, with worse DPFS observed in patients with a PSA-doubling time < 3 months (36.8% vs. 63.6%; P=0.029). Seventeen of 19 clinically relapsing patients presented lesions out of the ENRT field, and 10 were again oligometastatic. Only 2 patients presented with a CTCAE v3.0 grade >= 2 genitourinary toxicity. Conclusions: ENRT combined with short-course ADT is a safe and effective salvage modality for patients with oligorecurrent nodal PCa. Prospective randomized studies comparing focal SBRT versus ENRT are warranted to define the best treatment strategy.