Small cell carcinoma (SCC) of the prostate is a rare and recently recognized subtype of
prostate cancer. The neuroendocrine component of the prostate
carcinoma is becoming more frequently detected in classic
adenocarcinoma of the prostate. Clinically, these
tumors represent a considerable portion of so called
androgen independent prostatic
carcinomas. It has been hypothesized that the neuroendocrine cells being admixed with
adenocarcinoma is selected and emerges as a
hormone refractory
carcinoma after the
androgen blockade. The SCC shows a spectrum from a mixed
adenocarcinoma with SCC component to the extreme case of pure SCC. Characteristically, prostatic SCC shows low measurable serum level of traditional prostate
tumor marker, prostatic specific
antigen (PSA). Instead, SCC secretes several neural
peptides and
calcitonin (CT) is one of them. The usefulness of serum CT as a neuroendocrine marker was evaluated retrospectively in 16 patients with SCC of the prostate (5 pure SCCs and II combined
adenocarcinoma and SCCs). The serum CT was measured by radioimmunoassay. In all the patients, serum CT level was measured after SCC was diagnosed histologically. All 16 patients presented with advanced
tumor with extensive
metastasis. Nine (56 percent) out of 16 cases showed elevated serum CT (range 42 approximately 2,654 pg/ml) and chemically supported the diagnosis of SCC. Owing to the retrospective nature of the study, the serum CT was measured only once in most of the cases, and the value of monitoring the disease progress or the responsiveness to the
chemotherapy could not be evaluated. Survival analysis by logrank test did not show statistically significant prognostic value of serum CT in SCCs of the prostate. However, patients with extremely high serum CT level tend to have poor survival. Future studies are needed for further evaluation of serum CT as a disease monitor and prognostic marker in SCC of the prostate. Serum CT may have a role as a
tumor marker in the early diagnosis of SCC of the prostate, which often is not diagnosed until the advanced stage.