Predictors of long-term survival for localized prostate cancer treated with high-dose IMRT stratified by NCCN 2015 guidelines in a community hospital setting

The primary goal of this study is to determine prognostic factors associated with freedom from biochemical failure (FFBF) and survival for men with localized prostate cancer treated with intensity-modulated radiation therapy (IMRT) stratified according to the NCCN 2015 guidelines in a community hospital setting. A secondary objective is to evaluate long-term toxicity at last follow-up compared to pretreatment status (bowel, bladder, and sexual functioning) using a modified Radiation Therapy Oncology Group (RTOG) toxicity grading system. A final objective is to compare our results of IMRT in a community-based radiation practice to published results from academic institutions.

Two hundred and twenty-eight consecutive men treated with IMRT for organ-confined prostate cancer at Delaware County Memorial Hospital (DCMH) from 2003 when the IMRT program began to 2012 were reviewed on this IRB-approved retrospective study. Biochemical failure was assessed using the Phoenix Nadir +2 definition. CT and MRI treatment planning was used and treatment volumes included prostate +/− seminal vesicles and true pelvic lymph nodes depending on risk assessment based on pretreatment prognostic factors. Median dose to the prostate was 75.6 Gy. Median follow-up for the entire group was 72 months.

Ten-year actuarial FFBF for the entire group was 83.2 %. Eight-year actuarial FFBF stratified by 2015 NCCN risk stratification was 95.2 % very low risk, 96.3 % low risk, 81.5 % intermediate risk, 75.4 % high risk, and 38.7 % for the very high risk group (p = 0.02). Patients with PSA <30.65 had improved 8-year FFBF of 85.9 % compared with 46.1 % for PSA >30.65 (p = 0.0001). Multivariable analysis revealed only the five NCCN risk groups were independent prognosticators for FFBF. Ten-year actuarial survival for the entire group was 61.1 %. Only 8 deaths were secondary to prostate cancer out of 59 total deaths (13.6 %). Ten-year actuarial overall survival stratified by 2015 NCCN risk stratification was 68.8 % very low risk, 81.5 % low risk, 67.2 % intermediate risk, 46.3 % high risk, and 54.9 % for the very high risk group (p = 0.02). Ten-year overall survival rates stratified by age less than or greater than 71.5 were 75.9 % for age ≤71.5 and 55.2 % for age >71.5 (p = 0.01). Multivariable analysis revealed only age was an independent significant factor for survival with p = 0.0008. Grade 3 GI toxicity at last follow-up was 0.5 % with no grade 4 toxicities. Grade 3 GU toxicity at last follow-up was 1 % with no grade 4 toxicities. FFBF and toxicity rates are comparable to those reported by academic institutions and literature review of published data with comparison to our community hospital data will be presented.

The outcome of IMRT for men with prostate cancer treated in a community hospital is comparable to that of published literature from academic institutions. NCCN 2015 risk stratification is prognostic for FFBF. Age at diagnosis was the only significant independent predictor of survival, suggesting that cancer-specific mortality is minimized after IMRT in localized prostate cancer.