Plasma chromogranin A: Clinical implications in patients with castrate resistant prostate cancer receiving docetaxel chemotherapy

Objective: Development of castrate resistant prostate cancer (CRPC) indicates progressive disease with poor survival. Docetaxel has variable response with a good proportion of nonresponders. Neuroendocrine differentiation, hypothesised as one of the mechanisms behind development of CRPC, can be assessed by plasma Chromogranin A (CgA). We evaluated the clinical importance of circulating CgA in CRPC patients receiving Docetaxel. Methods: Plasma CgA was assessed by ELISA in 14 patients with CRPC receiving 3-weekly docetaxel. Baseline PSA, baseline CgA, PSA response, CgA response and clinical response to chemotherapy were evaluated and analysed. Results: Increased plasma CgA was observed in 64.3% of patients. There was no correlation between baseline CgA and PSA. Two patients with PSA < 10 ng/ml had elevated CgA. Baseline CgA was not influenced by variables such as site of metastasis and time to develop CRPC status. Seven patients (50%) had PSA-response and 5 (36%) CgA-response. In 4 patients PSA response and CgA response were discordant. Compared to men with normal baseline CgA, a higher proportion of those with elevated baseline CgA had PSA response (55% vs 40%), symptomatic response (66% vs 40%) and radiological response (55% vs 20%). Two patients with symptomatic response had only CgA response. Three patients having disease progression despite PSA response had increasing CgA. Conclusions: CgA and PSA are complementary tumour markers in CRPC. CgA may help in predicting the response of docetaxel therapy. Rising CgA during therapy may be associated with bad prognosis whereas CgA response is likely to be associated with clinical response.