Evaluation of the response of unresectable carcinoid tumors to radiotherapy

Sixteen patients with unresectable primary or metastatic carcinoid tumors were treated with radiotherapy. Objective responses (CR + PR) were documented in 4 of 16 patients (25%). The median survival of the responders was 46 months following radiotherapy, as compared to the 10-month median survival of the entire group of 16 patients. There were five additional patients who improved symptomatically or had minor responses. The seven patients who received the highest doses of radiotherapy (greater than 29 GY), to local or regional treatment ports, had the best response rate (43%). Many patients eventually had objective evidence of relapse or tumor progression within the radiotherapy port, in part reflecting the relatively low radiotherapy doses used in the treatment of the nine patients with abdominal carcinoids. One patient remains disease free at 103 months. Patients who exhibited the carcinoid syndrome appeared to respond less frequently to radiotherapy than patients who did not have ectopic hormone secretion, although the number of patients with ectopic hormone secretion was too small to establish this point in a definitive manner. The results of this study demonstrate that carcinoid tumors respond to moderate doses of radiotherapy in a manner similar to many other epithelial tumors.