Abstract 215P
Background
Peptide Receptor Radionuclide Therapy (PRRT) and Capecitabine/Temozolomide (CAPTEM) are cornerstones of systemic therapy for metastatic pancreatic neuroendocrine tumors (PNETs). The best sequence of systemic therapies (STs) in PNETs is poorly understood. Herein we compare the efficacy of PRRT vs. CAPTEM as 2nd line and beyond STs.
Methods
Clinicopathologic, radiographic, and genomic data were captured for metastatic PNET patients seen in our multi-disciplinary NET clinic between 2013 to 2023. The primary outcome was progression free survival (PFS) with PRRT/CAPTEM after progression on at least one prior line of ST. The secondary outcomes were objective response rate (ORR), time to response (TTR), and overall survival (OS). Outcomes were analyzed using Kaplan Meier estimations and Cox proportional hazards regression.
Results
59 patients were included and the median follow-up time was 31.7 months (m). There was no difference in PFS between the PRRT (n = 29) and CAPTEM (n = 30) groups (21.9 m vs. 20 m; HR, 0.99; p = 0.97). On subgroup analysis, PRRT had longer PFS in cases without extrahepatic metastases (n = 20; 26.5 m vs. 17.7 m; HR, 0.31; p = 0.03) and cases with mutations in the MEN1, DAXX, and/or ATRX genes (n = 19; 28.4 m vs. 18.7 m; HR, 0.22; p = 0.03). CAPTEM had longer PFS in patients with grade 3 disease (n = 13; 16.3 m vs. 7.8 m; HR, 0.13; p = 0.02) and trended towards longer PFS in cases with bone metastases (n = 20; 28.6 m vs. 17.9 m; HR, 0.35; p = 0.09). ORR did not vary significantly (PRRT, 8/23, 34.78%; vs. CAPTEM, 9/22, 40.91%; p = 0.67). CAPTEM responders showed shorter TTR (6.03 m vs. 11.15 m; log-rank p = 0.03). In patients who received both (PRRT first = 11; CAPTEM first = 12), OS did not vary based on the sequence (48.6 m vs. 50 m; HR, 1.20; p = 0.75).
Conclusions
PFS, ORR, and OS are similar when using PRRT vs. CAPTEM as 2nd line and beyond therapy for patients with metastatic PNETs. However, patients with MEN1, DAXX, and/or ATRX mutations or without extrahepatic metastases might further benefit from PRRT and patients with grade 3 disease from CAPTEM. Candidates for surgical debulking or those with tumor-induced symptoms may benefit from initial treatment with CAPTEM due to shorter TTR.
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
C. Liao: Other, Personal, Speaker’s Bureau: AstraZeneca, Incyte; Other, Personal, Other, Consultant: Genentech, Histosonics, Incyte, AstraZeneca, Ipsen, QED, Transthera, Boston Scientific. All other authors have declared no conflicts of interest.