Outcome analyses in patients with metastatic gastroenteropancreatic neuroendocrine tumors receiving peptide receptor radionuclide therapy with 177Lu-DOTATATE – Impact of treatment order and combination on mortality.

Abstract

4606 Background: Neuroendocrine tumors of the gastroenteropancreatic tract present heterogeneous with several systemic treatment options in the advanced setting. PRRT with 177Lu-DOTATATE targeting the SSTR-2 receptor of these tumors showed effective responses in the NETTER-1 trial in the short as well as long term follow-up of patients. The aim of our study was to determine the HRQoL and outcome of GEP-NET patients. Methods: 41 GEP-NET patients who received 177Lu-DOTATATE (mean: 3 cycles) between 2012 and 2017 at University Hospital Zurich (USZ) were included in this retrospective analysis. HRQoL parameters (fatigue, insomnia, loss of appetite, abdominal pain, nausea, emesis, diarrhea, weight loss) were assessed before and after treatment. At least 3 weeks after the last PRRT cycle, data on blood parameters, HRQoL, and overall survival data were extracted from patient records. To determine factors influencing the success of PRRT therapy and survival, we recorded pre- and post-PRRT treatments (e.g. selective internal radiation therapy/SIRT, somatostatin analogue therapy/SSA, TKI or chemotherapy) and the time-point of PRRT in the therapeutic sequence was analyzed. Results: Baseline rates of HRQoL and ECOG performance status were assessed (baseline mean: ECOG 0). PRRT was well tolerated, with most patients reporting no significant deterioration in HRQoL after treatment. Blood parameters (hemoglobin, leucocyte and platelet counts, creatinine) and glomerular filtration rate were not significantly affected by PRRT therapy. The number of previous treatments did not influence survival after PRRT; neither did the length of the time period between first diagnosis and PRRT. Patients with a SIRT treatment prior to PRRT had an elevated mortality odds ratio of 4.083. If SIRT was applied to patients with a pancreatic tumor, the mortality odds ratio was 1.33 compared to patients without a pancreatic tumor. Post-PRRT SSA increased the odds for survival, with a mortality odds ratio of 2.33 for patients without SSA after PRRT. Conclusions: Patients with advanced GEP-NETs may benefit from PRRT with 177Lu-DOTATATE, as this treatment appears to be well tolerated and does not significantly impair the HRQoL or symptom load. SIRT before PRRT seems to lower the chances of response and reduces survival instead using this sequence vice versa. This trend was also seen if SSA was not used after PRRT. But these trends have to be proven in prospective trials.