Retrospective analysis of Peptide Receptor Radionuclide Therapy (PRRT) in Japanese patients with unresectable neuroendocrine tumor.

e16700 Background: Peptide receptor radionuclide therapy (PRRT) with radiolabeled somatostatin analogues is an innovative treatment for inoperable or metastasized, well/moderately differentiated, neuroendocrine tumors (NETs). Currently PRRT cannot be performed in Japan, because there is no approval and insurance cover until now. Methods: We rely on University Hospital Basel to perform PRRT for Japanese patients with NET since 2011. In this retrospective analysis we evaluated the efficacy and safety of PRRT for Japanese patients with NET (IRB B180100019). Inclusion criteria were pathologically confirmed NET, inoperable or metastasized disease, and visible tumor uptake in the pre-therapeutic somatostatin receptor scintigraphy. We excluded patients with concurrent antitumor treatment, concomitant severe illness, and pre-existing severe hematologic, renal, and liver damage. 5.55GBq(150mCi) of 177Lu-DOTATOC was used as standard treatment and patients received three infusions every 8 weeks. Until end of 2017, combination treatment with 90Y-DOTATOC and 177Lu-DOTATOC was performed using the same protocol. We checked blood count and renal function parameter every two weeks after PRRT. CT or MRI examination were performed 10-12 weeks after the last PRRT cycle. We evaluated the morphological changes according to RECIST 1.1 criteria. With the execption of Somatostatin analogues further treatments were refrained until tumor progression. Results: Thirty-three patients (male: 16, female: 17) were recruited with a median age of 56 years. (range: 26-71). Primary lesions were pancreas (n = 18), rectum (n = 6), small intestine (n = 3), stomach (n = 1), and other locations (n = 5). The period between diagnosis and PRRT was about 3years. Median Ki67 index was 6.3% (range: 0.7%-30%). Partial response rate was 39.3% and disease control rate is 63.6%. Progression free survival (PFS) was 421 days (95%CI:269-572 days) and overall survival was 580 days (95%CI:259-900days). We compared PFS with the treatment line (front line: first or second-line vs late line: third or fourth-line), there was no significant difference between the two groups (front line: 329.0 days vs late line: 497.0 days Log Rank test P = 0.189). Conclusions: PRRT in Japanese patients with NET was effective and a reliable treatment option.