Long-term efficacy of radionuclide therapy in patients with disseminated neuroendocrine tumors uncontrolled by conventional therapy

Abstract

Therapeutic options in patients with advanced-stage gastroenteropancreatic (GEP) neuroendocrine tumors are limited. We compared the efficacy of radionuclide therapy with 111In-pentetreotide and 131I-metaiodobenzylguanidine (MIBG) in 20 patients (group A) with the outcome of similar patients who could not be treated for nonmedical reasons (group B, n = 12). The intent was to treat all patients because of uncontrolled tumor disease (n = 21), contraindication to chemotherapy or surgery (n = 7), or uncontrolled and badly tolerated clinical symptoms (n = 4).

Methods: Group A patients received 3 monthly administrations of 3.7-7.4 GBq of 131I-MIBG (n = 5) or 7 GBq of 111In-pentetreotide (n = 15), according to the best tracer uptake. Clinical evaluation, biologic tests, and conventional imaging were performed at 3, 6, 12, 18, and 24 mo. Therapy was considered beneficial if clinical status improved, laboratory tests for secreting tumors improved by >20%, tumor progression was halted, the size of the most significant localization had decreased by >25%, and the dosage of analgesic and cold somatostatin therapy could be lowered. Pejorative events were defined as side effects due to therapy, relapse in clinical symptoms, tumor progression, tumor laboratory marker increase, and death.

Results: The overall survival rate at 3 mo was significantly higher in group A (P = 0.05). Radionuclide therapy was beneficial in 14 patients (73% of group A), with only 1 significant side effect. The average time before relapse was 16.1 +/- 7.8 mo. The overall Kaplan-Meier survival rate and cumulative progression-free and cumulative event-free survival rates during the first 15 mo were significantly higher in patients receiving radionuclide therapy (P = 0.019, P = 0.024, and P = 0.019, respectively).

Conclusion: Radionuclide therapy is feasible and safe and significantly defers the occurrence of fatal and nonfatal events in patients clinically uncontrolled by conventional therapy.