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PHILADELPHIA -- Following initial therapy, salvage therapy with a peptide receptor radionuclide agent, ¹⁷⁷Lu-DOTA,Tyr³-octreotate, was beneficial for those with bronchial or gastroenteropancreatic neuroendocrine tumors, researchers reported here.

Among 168 patients evaluated for efficacy, those undergoing retreatment with the agent -- having benefited from initial treatment but later showing renewed tumor progression -- had median progression-free survival of 35.4 months (95% CI 33.0-40.7), according to Wouter van der Zwan, MD, of Erasmus Medical Center in Rotterdam, The Netherlands, and colleagues.

Patients who had re-retreatment had median progression-free of 14.2 months (95% CI 9.8-18.5); median overall survival time for all retreated patients (including those retreated once and those retreated a second time) was 80.8 months (95% CI 66.0-95.6).

The were presented at the 10th annual symposium of the North American Neuroendocrine Tumor Society and involved 181 patients retreated after an initial response to the ¹⁷⁷Lu-DOTA,Tyr³-octreotate agent, plus a control group of 230 patients who underwent initial therapy and qualified for retreatment but did not receive it. Median progression-free survival in the control group after initial therapy was 35.5 months, essentially identical to that seen in the retreated patients, but their overall survival was significantly shorter than those retreated (median 51.4 months, P<0.01).

Initial treatment involved a total cumulative dose of 29.6 GBq (800 mCi), given in four doses. Retreatment called for an intended cumulative dose of 44.4 GBq (1,200mCi) split in two doses. Those patients who had re-retreatment were administered a cumulative dose of 59.2 GBq (1,600mCi) in two doses of the ¹⁷⁷Lu-DOTA,Tyr³-octreotate agent.

In a safety analysis of all 181 patients, there was not a significant increase in the incidence of acute myeloid leukemia and myelodysplastic syndrome when compared (3.5% control versus 2.2% retreatment group; P=0.56).

After initial treatment, retreatment, and re-retreatment, the incidence of grade III and IV bone marrow toxicity were 10.0%, 7.7%, and 7.1%, respectively.

"Up to a cumulative 1600 mCi [59.2 GBq] salvage PRRT with [¹⁷⁷Lu-DOTA,Tyr³]-octreotate can be performed safely and effectively," the authors concluded.

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