Real world sequence of peptide receptor radionucleotide therapy (PRRT) and chemotherapy in patients with metastatic pancreatic neuroendocrine tumors (pNETs).

Abstract

e16237 Background: Peptide Receptor Radionuclide Therapy (PRRT) is an effective therapy for advanced pNETs but carries long-term risks of myeloid neoplasia. Early data from United States centres may suggest a higher risk of myelodysplasia and leukemia in patients treated with temozolomide prior to PRRT. The objective of this study is to characterize the sequence of PRRT and chemotherapy at two Canadian pNET treatment centres, distinguished by the availability of PRRT. Methods: This is a multicentre retrospective cohort study involving The Ottawa Hospital Cancer Centre (TOHCC; PRRT non-treatment centre (PRRT-NTC)) and London Regional Cancer Centre (LRCC; PRRT treatment centre (PRRT-TC). Patients with histologically confirmed pNETs between January 2010 – June 2021 over the age 18 (n=226), with metastatic disease (n=177) were included. Demographic, clinical and cancer treatments were collected. Descriptive statistics were used to evaluate the sequence of systemic therapy. Results: 177 patients with metastatic pNET were identified. Systemic therapies included octreotide (n=59, 40%), lanreotide (n=47, 32%), targeted agents (n=40, 27%), chemotherapy (n=48, 33%) and PRRT (n=47, 32%). Of patients receiving chemotherapy, 22 (46%) received temozolomide-containing regimens. The most frequent first line therapies were somatostatin analogues (SSAs, n=76, 43%), chemotherapy (n=23, 13%) and observation (n=18, 10%), second-line were PRRT (n=24, 14%), targeted therapy (n=26, 15%) and SSA (n=13, 7%), and third-line were PRRT (n=15, 9%), chemotherapy (n=11, 6%) and targeted therapy (n=8, 5%). There were 83 (47%) patients treated at the PRRT-TC, of which 33 (40%) received PRRT prior to chemotherapy and 7 (8%) received temozolomide-containing therapy prior to PRRT. In comparison, 94 (53%) patients were treated at the PRRT-NTC, of which 1 (1%) received PRRT prior to chemotherapy and 0 (0%) received PRRT prior to temozolomide-containing therapy. Conclusions: In this large cohort of metastatic pNET patients, the sequence of chemotherapy and PRRT showed centre-to-centre variability with patients treated at a PRRT-TC being more likely to receive chemotherapy, including temozolomide, prior to PRRT. This may be explained in-part by referral/practice patterns, and PRRT availability. These findings suggest an opportunity to evaluate and optimize the sequence of systemic therapy with the increasing availability of PRRT.