Histological subtypes of prostatic cancer: a comparative survival study

Variant histological subtypes of prostatic cancer occur uncommonly and are associated with poor survival, as has been ascertained through limited series and case reports. Here a population-based analysis of prostatic cancer is provided, to better analyze the survival behavior of these subtypes.

The American SEER registry was used to review prostatic cancer diagnosed from 1988 to 2003, classified according to the International Classification of Diseases for Oncology. Kaplan-Meier and proportional hazards analyses were performed on adenocarcinomas and five infrequent variant subtypes to determine their overall survival behavior, allowing corrections for follow up inequity, age, stage, histological grade, and year of diagnosis.

A total of 455,296 cases of prostatic cancer were reviewed, of which over 99% were conventional adenocarcinomas. The remaining variants studied included ductal carcinomas (0.141%), mucinous adenocarcinomas (0.103%), small cell carcinomas (0.056%), carcinosaromas (0.07%) and embryonal carcinosarcomas (0.06%). With age, stage and grade effects were corrected for in the multivariate analysis, conventional adenocarcinomas, mucinous adenocarcinomas and ductal carcinomas exhibited similar survival behavior. Small cell carcinomas and carcinosarcomas exhibited poor survival, even with correction. The embryonal variant of carcinosarcoma affected pediatric patients and had an overall survival similar to conventional prostatic cancer. Ductal carcinomas, small cell carcinomas and both types of carcinosarcoma tended to present with metastases more frequently than conventional disease.

Prostatic cancer subtype can have a major bearing on overall survival and likely reflects intrinsic differences in biological behavior.