Temozolomide as monotherapy is effective in treatment of advanced malignant neuroendocrine tumors

Purpose: A retrospective analysis of the toxicity and efficacy of temozolomide in advanced neuroendocrine tumors. Experimental Design: Thirty-six patients with advanced stages of neuroendocrine tumor (1 gastric, 7 thymic and 13 bronchial carcinoids, 12 pancreatic endocrine tumors, 1 paraganglioma, 1 neuroendocrine foregut, and 1 neuroendocrine cecal cancer) were treated with temozolomide (200 mg/m(2)) for 5 days every 4 weeks. Patients had previously received a mean of 2.4 anti-tumoral medical regimens. Tumor response was evaluated radiologically according to the Response Evaluation Criteria in Solid Tumors every 3 months on an intent-to-treat basis. The circulating tumor marker plasma chromogranin A was also assessed. The expression of O-6-methylguanine DNA methyltransferase, an enzyme implicated in chemotherapy resistance, was studied by immunohistochemistry (n = 23) and compared with response to temozolomide. Results: Median overall time to progression was 7 months (95% confidence interval, 3-10). Radiologic response was seen in 14% of patients and stable disease in 53%. Side effects were mainly hematologic; 14% experienced grade 3 or 4 thrombocytopenia (National Cancer Institute toxicity criteria). Ten patients had tumors with O-6-methylguanine DNA methyltransferase immunoreactivity in < 10% of nuclei, whereas four patients showed radiologic responses. Conclusions: Temozolomide as monotherapy had acceptable toxicity and antitumoral effects in a small series of patients with advanced malignant neuroendocrine tumors and four of these showed radiologic responses.