Background: The American Joint Commission on Cancer (AJCC) identifies five rare variants of prostate adenocarcinoma: mucinous, ductal, signet ring cell, adenosquamous and neuroendocrine including small cell. No prior study has comprehensively detailed incidence and outcomes for all AJCC variants of prostate cancer.
Methods: We used the Surveillance, Epidemiology and End Results (SEER) program to analyze prostate cancers diagnosed from 1973 to 2008. Cases of mucinous, ductal, signet ring cell, adenosquamous and neuroendocrine carcinoma were identified, along with cases of non-variant adenocarcinoma for comparison. Age-adjusted incidence rates (IRs) and overall survival (OS) were evaluated and stratified by race, age, stage and PSA. All IRs represent the number of cases per million people per year.
Results: Each variant is rare, with IRs between 0.03 (adenosquamous) and 0.61 (mucinous). There was a significant difference in incidence between Caucasian and African American patients with mucinous adenocarcinoma. Median OS varied ranged from 10.0 months in neuroendocrine carcinoma to 125.0 months in mucinous adenocarcinoma. In all, 5-year OS ranged from 12.6% in neuroendocrine carcinoma to 75.1% in mucinous adenocarcinoma. There was a significant difference in survival between Caucasian and African American patients for mucinous adenocarcinoma (median survival 144.0 vs 99.0 months, P<0.01). African American patients with mucinous adenocarcinoma also presented with more advanced stage disease compared with Caucasian patients. Multivariate analysis demonstrated that African American race was not associated with worse survival when corrected for stage.
Conclusions: There are differences in IRs and OS among rare variants of prostate cancer. For mucinous adenocarcinoma, there are significant differences in incidence and survival between Caucasian and African American patients. These differences should be considered in clinical decision making for patients with these malignancies.