Mid-Treatment Response to 177-Lutetium Dotatate Predicts Overall Outcome in Patients with Advanced Neuroendocrine Tumors

PURPOSEPatients with advanced, well-differentiated neuroendocrine tumors (WD-NETs) often require both peptide receptor radionuclide therapy (PRRT) and subsequent chemotherapy. However, no mid-PRRT predictors are available to identify patients who will not benefit from subsequent PRRT to limit their radiation exposure. Our aim is to characterize patients for whom subsequent PRRT is less efficacious on the basis of mid-PRRT evaluation.MATERIALS AND METHODSA retrospective study of patients with WD-NET who underwent ‰¥four PRRT cycles. Data gathered included demographics, tumor grade, stage, and response (partial response [PR], stable disease [SD], and progressive disease [PD]) on the basis of RECIST 1.1 criteria and 68Ga-dotatate positron emission tomography-computerized tomography pretreatment, after second and fourth treatment cycle, 6 months after fourth cycle, and at last follow-up.RESULTSFifty-one patients (51.6% women; age at diagnosis 66.0 ± 1.65 years), with pancreatic NET (PNET; n = 24), small intestine NET (n = 13), or other NET (n = 14), received PRRT, resulting in PR (n = 21), SD (n = 23), and PD (n = 3). Of the patients reaching PR after PRRT, most reached PR after two treatments (70.4%), with only 11.8% PR occurring between subsequent cycles (P =.001). Furthermore, patients with PR at mid-Treatment had higher PR rates after PRRT completion than those with SD (P =.007). Patients harboring PNET who achieved PR had a more pronounced reduction of tumor burden in additional cycles than patients who did not (25.6% v 1.5%; P =.03, respectively). On the multivariable model, adjusted for grade and primary site, PR at mid-Treatment evaluation was associated with a 20.9 adjusted odds ratio for additional PR at PRRT completion (P =.002).CONCLUSIONMid-PRRT assessment predicts subsequent PRRT response in patients with WD-NET, especially those with PNET, informing personalized management and consideration of reduced bone marrow radiation exposure in high-risk patients.