Outcomes of high-dose whole pelvic simultaneous integrated boost IMRT in patients with pelvic lymph node-positive prostate cancer.

Abstract

192 Background: Managements of prostate cancer patients with positive pelvic lymph node (N1M0) have been very challenging. We evaluated the outcomes of high-dose whole pelvic (WP) intensity-modulated radiation therapy (IMRT) by using the simultaneous integrated boost (SIB) technique, combined with long-term androgen deprivation therapy (ADT). Methods: Between May 2005 and November 2013, 52 patients with T2a-T4N1M0 prostate cancer were definitively treated by WP SIB-IMRT. Pelvic lymph node metastases were clinically diagnosed based on the following criteria; depicted swollen lymph nodes on diagnostic imaging associated with subsequent shrinkage in size on a follow-up imaging after neoadjuvant ADT (NA-ADT). The median age and initial PSA value were 66 years old (range: 52–79) and 29.7 ng/ml (4.8–251.9), respectively. NA-ADT (median: 8 months, range: 5–20) was given in all cases. SIB WP-IMRT was designed to simultaneously deliver 78 Gy, 66.3 Gy, and 58.5 Gy in 39 fractions to the prostate plus seminal vesicles, metastatic lymph nodes, and the pelvic lymph node region, respectively. Adjuvant ADT (A-ADT) was given in all patients except for one case who developed severe adverse events during NA-ADT. In 9 patients, permanent A-ADT was given due to castration after IMRT (n = 2) and development to castration resistant status during A-ADT (n = 7). The median duration of A-ADT was 24 months (range: 7–71) in the remaining 42 patients. Results: The median follow-up period was 69 months (range: 12–136). Biochemical relapse-free survival rate based on the Phoenix definition and distant metastasis-free survival rates at 5 years were 69% (95% CI = 54%–80%) and 78% (95% CI = 64%–87%), respectively. Overall survival and prostate cancer-specific survival rates at 5 years were 88% (95% CI = 74–94%) and 92% (95% CI = 79–97%), respectively. Loco-regional recurrence was not observed. 5-year cumulative incidence rates of grade 2-3 late GU and GI toxicities were both 2%. No grade 4 acute or late toxicity was observed. Conclusions: High-dose WP SIB-IMRT to patients with N1M0 prostate cancer seems promising, and warrants future prospective studies.