High-activity (111)In-pentetreotide has been used to treat patients with disseminated neuroendocrine tumors. There is, however, little information related to the efficacy of this agent beyond the normal 6-mo assessment period. Before we can assume that such treatment would be beneficial to patients with neuroendocrine tumors the outcome of the patients over a longer time course should be determined.
Methods: The case records of 16 patients who had received high activities of (111)In-pentetreotide (with cumulative activities as high as 36.6 GBq) over a 2.5-y period, from January 1, 1997, to June 30, 2000, were reviewed. There were 8 female and 8 male patients (age range, 32-76 y): 10 patients had carcinoid, 2 had medullary cell carcinoma of the thyroid, and 1 each had a gastrinoma, glucagonoma, fibrolamellar cancer, and malignant histiocytoma. The minimum number of treatments received was 1 in 2 patients (with activities of 3.1 and 7 GBq); the maximum was 10 treatments (total, 36.6 GBq). Treatment was given using an infusion pump and was repeated at 4- to 12-wk intervals (mean number of treatments per patient, 6). Response to therapy was determined by changes in the size of the tumor on CT using the response evaluation criteria in solid tumors. Toxicity was measured using blood and urine tests of renal, hepatic, thyroid, and bone marrow function. The mean and median time from the last treatment to progression of disease and death (if applicable) was also calculated.
Results: No significant or long-lasting toxicity was encountered. At 6 mo after the patient's last treatment, 5 patients (30%) had disease progression, 2 had complete responses, and 3 had partial responses. Twelve months after their last treatment, 9 patients (56%) had disease progression, and, at 18 mo, 11 patients (69%) had disease progression. The mean progression-free survival was 12.25 mo (median, 9 mo). For those who survived 6 mo after their last treatment, the mean survival was 15.75 mo (median, 16 mo). At the 6-mo assessment point, there had been 3 deaths (19%): 1 death was not related to cancer. At 12 mo, there was 1 additional cancer death. At 18 mo, there were 3 additional deaths (1 was not related to the patient's carcinoid tumor but was due to a second coexistent cancer). By the end of the 18-mo assessment period, 7 patients (44%) had died. The mean time interval between disease progression and death was 5 mo.
Conclusion: In patients treated with high-activity (111)In-pentreotide, 70% had some benefit for at least 6 mo after the end of treatment; however, 31% of patients will have sustained benefit at 18 mo from this treatment. This was obtained without significant toxicity.