Current trend of worsening prognosis of prostate small cell carcinoma: A population-based study

To determine the accurate age-adjusted incidence of prostate small cell carcinoma (SCC), update the clinical and pathological characteristics, as well as survival data of prostate SCC from Surveillance, Epidemiology, and End Results (SEER) datasets.

A total of 260 patients with prostate SCC were selected from the SEER database of the National Cancer Institute between 2004 and 2015. Age-adjusted incidence (AAI) rates, the observed and relative survival rates were evaluated over time by the SEER*Stat Software version 8.3.5. Overall survival (OS) rates that stratified by summary stage and treatment effects were evaluated by Kaplan-Meier method. The significant differences were assessed in a log-rank test. Univariate and multivariate cox hazard regression analysis were performed to determine independent predictors of OS.

The incidence of prostate SCC has increased over time. The average age of prostate SCC patients was 70.25 years. More than 90% of tumors were poorly differentiated or undifferentiated. The majority of prostate SCC (77.7%) was at stage IV. 49% of patients had lymph node metastases and 68% of patients presented distant metastases (Compared with 60.5% of patients with distant metastases between 1973-2003). Interestingly only 23.5% patients had high level PSA (>10 ng/mL). 58.8% of patients underwent chemotherapy, 25.4% of patients were treated by surgery, and 31.9% of patients were treated by radiotherapy. The observed survival rates of 1-year, 2-year, and 5-year were 42.1%, 22.1%, and 12.5%, respectively (Compared with 47.9%, 27.5%, and 14.3%, respectively, between 1973 and 2003). Chemotherapy prolonged the OS of patients with regional (distant) metastases from 3 months (2 months) to 12 months (9 months). Multivariate cox regression analysis showed age, race, and stage were independent prognostic factors for prostate SCC patients.

Prostate SCC is a highly malignant cancer and our analysis of recent data has shown its incidence is increasing. Incidence rate of metastatic prostate SCC has increased and the survival rates have worsened in recent years. However, chemotherapy shows some survival benefit for prostate SCC patients with regional and distant metastasis over other treatment methods. Further work is needed to understand the reason prognosis of this type prostate cancer is worsening.