Serum calcitonin in small cell carcinoma of the prostate

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 11 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 ~ 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.