Comparison of Response Evaluation in Patients with Gastroenteropancreatic and Thoracic Neuroendocrine Tumors After Treatment with [177Lu-DOTA0,Tyr3]Octreotate

UNLABELLED: Response Evaluation Criteria In Solid Tumors (RECIST) (unidimensional), Southwest Oncology Group (SWOG) solid tumor response criteria (bidimensional), and their modified variants are commonly used in the tumor response assessment after treatment of gastroenteropancreatic and thoracic neuroendocrine tumors (NETs). In the current study, RECIST, SWOG criteria, modified RECIST (mRECIST), and modified SWOG (mSWOG) criteria were compared in patients with NETs treated with [(177)Lu-DOTA(0),Tyr(3)]octreotate ((177)Lu-octreotate). METHODS: Two-hundred sixty-eight Dutch patients with NETs who had been treated with (177)Lu-octreotate between January 2000 and April 2007 were studied. CT or MR imaging scans were analyzed using RECIST, SWOG criteria, mRECIST, and mSWOG criteria (including the tumor response class minor response [decrease of 13%-30% for mRECIST and 25%-50% for mSWOG]). The outcomes were correlated with progression-free survival (PFS) and overall survival (OS). RESULTS: Eleven patients had an unknown tumor response and were excluded. The rates of objective response (OR) (complete response + partial response [+minor response for mRECIST/mSWOG]), stable disease, and progressive disease (PD) were 28%, 49%, and 24%, respectively, according to RECIST; 25%, 49%, and 26%, respectively, according to SWOG; 44%, 33%, and 24%, respectively, according to mRECIST; and 45%, 29%, and 26%, respectively, according to mSWOG. In patients who had OR, stable disease, or PD, the median PFS was 26-30, 27-34, and 8 mo, respectively, with any of the 4 response criteria. In patients who had OR, stable disease, or PD, the median OS was 55-57, 56-74, and 11-12 mo, respectively, with any of the 4 response criteria. Subanalyses for patients who had progression before treatment start were comparable. CONCLUSION: Patients with PD as treatment outcome had significantly shorter PFS and OS than patients with an OR or stable disease with all 4 scoring systems. PFS and OS were comparable for patients with tumor regression and stable disease. The addition of the response class minor response did not improve the correlation with PFS and OS. The 4 scoring systems gave comparable results in terms of PFS and OS per categorized outcome.