Radiotherapy for isolated lymph node metastases in patients with locally advanced prostate cancer after primary therapy

Purpose: To evaluate the outcome of radiotherapy for isolated lymph node metastases in patients with progression towards castration-resistant prostate cancer (CRPC) after definitive therapy. Methods: Between 11/2009 and 06/2014, 18 patients with isolated lymph node metastases after definitive prostate cancer therapy received radiotherapy to the affected lymph nodes with a total dose of 50.4 or 54.0 Gray (Gy). All patients had continuously rising levels of PSA despite androgen deprivation therapy (ADT). Biochemical progression-free survival (BPFS), clinical failure-free survival (CFFS) and freedom from local failure were assessed, as was the toxicity profile. Results: Of the 18 patients, 17 had high-risk prostate cancer. Radiotherapy was performed at a median interval of 64.55 [interquartile range (IQR) 23.2–153.8] months after definitive therapy. ADT was administered for a median (IQR) time of 3.8 (3.2–24.7) months prior to irradiation. The median (IQR) follow-up was 15.59 (5.3–28.5) months with 94.1 % freedom from local failure. The median BPFS and CFFS were 5.85 (IQR 3.0–20.3) and 9.60 months (IQR 5.9–28.8), respectively. No grade III acute or grade II late toxicity was observed. Only two patients developed local relapse. No patients exhibited deterioration of urinary or faecal continence. Conclusion: Radiotherapy of isolated lymph node metastases in patients who develop CRPC provides effective local control, is not associated with clinically important acute or long-term side effects, improves PSA kinetics and may delay the necessity of chemotherapy.