Patterns of care and treatment outcomes in locoregional squamous cell carcinoma of the prostate.

260 Background: Primary pure prostate squamous cell carcinoma (PSCC) is a rare, aggressive disease accounting for less than 0.5-1% of prostate cancer diagnoses. PSCC is a distinct entity from adenocarcinoma with historically poor outcomes, often presenting in younger patients with lower urinary tract symptoms and normal PSA. There are currently no established treatment guidelines. Case reports are limited but describe multiple treatment approaches including various combinations of surgery, platinum and non-platinum-based chemotherapy, radiotherapy and androgen deprivation therapy, with selected reports showing longer survival times with a combined modality approach. Methods: Seeking to identify practice patterns and treatment outcomes, we performed a retrospective analysis of the United States National Cancer Database to identify 66 males with locoregional, nonmetastatic primary pure squamous cell carcinoma of the prostate and treated with surgery, chemotherapy, and/or radiotherapy between 2004 and 2015. Clinical factors in analysis included pretreatment PSA, clinical T-stage, histology, treatment modality and demographic factors including age, comorbidity index, race, insurance status and treatment facility type. Patients were stratified into treatment groups consisting of local therapy alone (n = 40, 60%), local therapy and chemotherapy (n = 13, 20%), chemotherapy alone (n = 7, 11%), and observation (n = 6, 9%). Survival analysis was estimated using the Kaplan-Meier method and analyzed with log-rank testing. A Cox proportional hazards model was used to evaluate the association between patient characteristics and survival. Univariable and multivariable logistic regression was performed to identify covariates associated with receipt of each treatment modality. Results: With an overall median follow-up of 21.9 months, median survival was 19.7 months for patients treated with local therapy alone, 10.9 months with chemotherapy alone, and 36.5 months with combined local therapy and chemotherapy. Overall survival was not statistically significant between treatment groups. Statistically significant predictors of death included age (HR 1.1, 95% CI [1.03-1.17]) and clinical stage ≥T3a (HR 4.05, 95% CI [1.35-12.2]). Statistically significant predictors of receipt of chemotherapy were clinical stage T3a or greater (OR 34.6, 95% CI [2.65-364]) and age (OR 0.91, 95% CI [0.82-99]). Conclusions: This analysis represents the largest reported cohort analysis of locoregional pure PSCC. Unfortunately, due to the rarity of this disease, prospective or randomized trials to determine the optimal treatment strategy are not feasible. Despite limitations in sample size, and in the absence of prospective data, this analysis suggests the addition of chemotherapy to local therapy is a reasonable treatment approach in appropriately selected patients and may result in improved survival.