Clinical Response Profile of Metastatic/Advanced Pulmonary Neuroendocrine Tumors to Peptide Receptor Radionuclide Therapy with 177Lu-DOTATATE

Of 22 patients, 6 had undergone surgical resection of primary tumors. All patients were symptomatic before start of PRRT. Two patients did not qualify for PRRT, and 1 received single cycle with follow-up less than 3 months, hence excluded from the present analysis. Thus, a total 19 patients were analyzed in our study. Symptomatic response following PRRT was observed in 15 (79%) of 19 patients. Based on predefined 3-scale response evaluation criteria, of 19 patients, 12 patients (63%) were finally characterized as responders, and 7 patients (37%) were overall nonresponder to PRRT. All 7 nonresponders had moderate to intense FDG-avid primary lung lesion (SUVmax >5 in 4 of 7 patients), and 5 had FDG-avid metastatic liver disease (SUVmax >5). Peptide receptor radionuclide therapy was well tolerated in all with no major hematologic and renal toxicity (except for 2 patients showing mild grade I renal and hematologic toxicity in the initial cycles and recovery in subsequent follow-up). Seven (37%) of 19 died at the time of analysis. The observed annual OS rates were as follows: 1 year: 94.7% (95% CI, 68.1%-99.2%), 2 years: 66% (95% CI, 35.5%-84.5%), 3 years: 57.7% (95% CI, 28-78.9%), and 4 years: 38.5% (95% CI, 8.1%-69.5%); median OS was 40 months with 39% (95% CI, 13.1%-64.8%). In conclusion, Lu-DOTATATE PRRT was found safe and well tolerated in receptor-positive pulmonary NET. FDG positivity appeared to forecast aggressive tumor behavior.