切除不能・再発膵神経内分泌腫瘍（NETG2）に対し放射性核種標識ペプチド治療（PRRT）を施行した4症例の有効性及び安全性に関する検討

In June 2021, 177Lu-oxodotreotide, a PRRT, was approved by insurance for unresectable or recurrent NETs. We investigated the efficacy and safety of PRRT in four patients with P-NETs at our hospital. All patients were confirmed to be positive for somatostatin receptors by using octreoscan. PRRT treatment was then performed and retrospectively evaluated for efficacy and safety. PRRT was administered as lutetium oxodotreotide（177Lu） at 7.4 GBq per dose over 30 - minutes for up to 1 - 4 doses at 8 - week intervals. Efficacy was evaluated using RECIST v1. 1. Adverse effects were evaluated by CTCAE（v5.0 JCOG）.
The mean patient age was 60±12.0 years, and all patients were male. Three patients had a PS of 0, and one patient had a PS of 1 or higher. Metastatic organs were the liver in four patients and intra-abdominal lymph nodes in one patient, all of whom were Stage IV. Three patients underwent transarterial embolization. 177Lu-DOTATOC PRRT was administered every 8 weeks, and a total of four courses were administered in two patients, three courses in one patient, and one course in one patient. One patient had grade 2 thrombocytopenia after one course, and the second course was administered at a half dose（3.7 GBq）. The overall response rate（ORR） was 25%, with one PR and two SD. The median PFS was 9 months（95% Cl, 8-NA）, and the median overall survival from diagnosis was 119 months（95%Cl, 31 - NA）. Adverse events during PRRT included leukopenia in two patients（one G3, one G2）, lymphopenia in one patient（one G3）, thrombocytopenia in two patients（two G2, one G3）, creatinine increase in one patient（one G2）, and skin rash in one patient.
In conclusion, PRRT is expected to be highly effective and safe compared with conventional therapy for neuroendocrine tumors with unresectable or distant metastases.