Endocrine Abstracts

Background: Neuroendocrine tumours (NETs) are rare malignancies; over 60% of primary lesions arise in the gastrointestinal tract and pancreas. Despite several practice-changing clinical trials, uncertainty persists around the most efficacious treatment sequence in patients with advanced well-differentiated gastroenteropancreatic (GEP) NETs, particularly in relation to peptide receptor radionuclide therapy (PRRT). This study aimed to investigate the progression-free survival (PFS) of PRRT administered immediately after disease progression on a somatostatin analogue (SSA) (early) or following an alternative second-line therapy (later).

Methods: Data from patients who received PRRT for histologically-confirmed advanced GEP-NETs were analysed retrospectively. The Kaplan Meier method and Log-rank test were used to evaluate PFS and overall survival (OS) to assess any differences between the groups (PRRT early versus later).

Results: Of 147 patients who received PRRT for GEP-NETs between 24/05/2011-25/02/22, 134 potentially eligible participants were identified and 119 were included in the final analysis (15 excluded as they did not receive a first-line SSA) (median age 60 years; 51.3% male). Ninety-five patients [primary sites: small bowel: 61 (64%), unknown: 13 (14%), pancreas: 9 (10%), colon: 6 (6%), other: 4 (4%), rectum: 2 (2%); ECOG PS 0: 38 (40%), 1: 49 (52%), 2: 6 (6%); unavailable: 2 (2%), Grade: 1: 57 (60%), 2: 36 (38%), unavailable: 2 (2%)] received PRRT immediately after SSA (Group 1) and 24 patients [primary sites: pancreas: 11 (46%), small bowel: 9 (38%), rectum: 2 (8%), unknown: 2 (8%); ECOG PS 0: 11 (46%), 1: 13 (54%), Grade: 1: 12 (50%), 2: 12 (50%)] received PRRT later in their disease course (median number of intervening treatments: 1) (Group 2). Median PFS in Groups 1 and 2 was 40.7 (95% confidence interval (CI) 37.6-43.9) and 28.4 (95% CI 21.4-35.3) months, respectively (P= 0.297). Median OS for Groups 1 and 2 was 161.5 (95% CI 108.1-214.9) and 146.7 (95% CI 88.1-205.2) months, respectively (P= 0.308).

Conclusions: In this study, median PFS was not statistically significantly different in the group receiving PRRT early versus later. There was a trend towards improved PFS in the group receiving PRRT early, which may have been due to patient selection. Prospective studies are warranted.