Tumor Response and Clinical Benefit in Neuroendocrine Tumors After 7.4 GBq ⁹⁰Y-DOTATOC

Abstract

The aim of this prospective phase II study was to evaluate the tumor response of neuroendocrine tumors to high-dose targeted irradiation with 7.4 GBq/m² of the radiolabeled somatostatin analog ⁹⁰Y-1,4,7,10-tetra-azacyclododecan-4,7,10-tricarboxy-methyl-1-yl-acetyl-d-Phe-Tyr³-octreotide (DOTATOC). In addition, we investigated the clinical benefit of ⁹⁰Y-DOTATOC regarding the malignant carcinoid syndrome and tumor-associated pain. Methods: Thirty-nine patients (mean age, 55 y) with progressive neuroendocrine gastroenteropancreatic and bronchial tumors were included. The treatment consisted of 4 equal intravenous injections of a total of 7.4 GBq/m^{2 90}Y-DOTATOC, administered at intervals of 6 wk. After each treatment cycle, a standardized clinical benefit assessment using the National Cancer Institute grading criteria (NCI-CTC) was performed. Results: The objective response rate according to World Health Organization (WHO) criteria was 23%. For endocrine pancreatic tumors (13 patients), the objective response rate was 38%. Complete remissions were found in 5% (2/39), partial remissions in 18% (7/39), stable disease in 69% (27/39), and progressive disease in 8% (3/39). A significant reduction of clinical symptoms could be found in 83% of patients with diarrhea, in 46% of patients with flush, in 63% of patients with wheezing, and in 75% of patients with pellagra. The overall clinical benefit was 63%. All responses (both clinical benefit and WHO response) were ongoing for the duration of follow-up (median, 6 mo; range, 2–12 mo). Side effects were grade 3 or 4 (NCI-CTC) lymphocytopenia in 23%, grade 3 anemia in 3%, and grade 2 renal insufficiency in 3%. Conclusion: High-dose targeted radiotherapy with 7.4 GBq/m^{2 90}Y-DOTATOC is a well-tolerated treatment for neuroendocrine tumors, with remarkable clinical benefit and objective response.