Ten‐year outcomes of whole‐pelvic intensity‐modulated radiation therapy for prostate cancer with regional lymph node metastasis

BACKGROUND: Management of pelvic node‐positive prostate cancer has been challenging and controversial. We conducted a study to evaluate the outcomes of whole‐pelvic (WP) simultaneous integrated boost (SIB) intensity‐modulated radiation therapy (IMRT) combined with androgen deprivation therapy (ADT). METHODS: A total of 67 consecutive patients with cT1c‐4N1M0 prostate cancer were definitively treated by WP SIB‐IMRT. Neoadjuvant ADT (median: 8.3 months) was administered in all cases. WP SIB‐IMRT was designed to simultaneously deliver 78, 66.3, and 58.5 Gy in 39 fractions to the prostate plus seminal vesicles, metastatic lymph nodes (LNs), and the pelvic LN region, respectively. Adjuvant ADT (median: 24.7 months) was administered in 66 patients. RESULTS: The median follow‐up period was 81.6 months (range: 30.5–160.7). Biochemical relapse‐free, overall, and prostate cancer‐specific survival rates at 10 years were 59.8%, 79.6%, and 86.3%, respectively. Loco‐regional recurrence was not observed. Being in International Society of Urological Pathology grade group 5 and having a posttreatment detectable nadir prostate‐specific antigen (PSA) level (≥0.010 ng/ml) were significantly associated with worse prostate cancer‐specific survival and progression of castration resistance. The 10‐year cumulative incidence rates of grade 2 and 3 late toxicities were, respectively, 1.5% and 0% for genitourinary, 0% and 1.5% for gastrointestinal events. No grade 4 acute or late toxicities were observed. CONCLUSIONS: WP SIB‐IMRT can be safely administered to patients with pelvic node‐positive prostate cancer. Since grade group 5 and detectable nadir PSA levels are risks for castration resistance, we may need to increase the intensity of treatment for such cases.