1324P - The role of modulation of somatostatin analogues (SSAs) in association to peptide receptor radionuclide therapy (PRRT) after SSAs progression disease (PD) in advanced well-differentiated (WD) entero-pancreatic neuroendocrine tumours (EP-NETs)

Abstract

Background: The NETTER-1 trial has recently shown the efficacy of 177Lu-DOTATATE in association with Octreotide (OCT) in somatostatin receptor positive midgut NETs, progressing to OCT. The aim of this analysis was to evaluate the role of SSA in association to PRRT beyond PD or after switch to other SSA at PD. Methods: Out of 107 WD EP-NETs, treated with PRRT (90Y-DOTATOC/DOTATATE and/or 177Lu-DOTATOC/DOTATATE) at the Istituto Nazionale Tumori of Milan, from 2008 to 2017, 69 patients (pts) treated with the combination of PRRT and SSA (OCT or Lanreotide, LAN) after SSA treatment failure, were evaluated for present analysis. We identified 2 groups: S1, pts who kept the same SSA treatment beyond first PD; S2, pts who switched the SSA with another SSA after first PD. Median Progression Free Survival (mPFS) (from the start of first SSA) and Overall Survival (OS) have been evaluated using the Kaplan-Maier method. Results: In S1 (n = 47) and S2 (n = 22) groups median age and sex were 58 ys (range 29-78) and 59.5% males vs 52.5 ys (range 35-78) and 45.4% males, respectively. We had a P-NETs percentage of 34% vs 40.9% in the S1 vs S2 groups, respectively. The most of pts (82.9% in S1 and 86.3% in S2) received PRRT with alternate radionuclides (90Y/177Lu). Overall the median number of PRRT cycles was 4.2 in S1 and 4.8 in S2 (p = 0.09). In the S1 (SSA beyond PD) group PRRT was associated with OCT in 74.5% and LAN in 25.5% of pts. In the S2 group (SSA switched with other SSA) PRRT was associated with OCT in 27.3% and LAN in 72.7% of pts. In the overall population the mPFS and OS were 70 (CI95% 52.8-87.1) and 82 (CI95% 66.7-97.2) months (mo), respectively. The difference on mPFS was 53 and 127 mo in S1 and S2, respectively (p = 0.001; HR: 0.31; CI95% 0.15-0.63). In S1 group the OS was 69 mo vs 150 mo in S2 (p = 0.004; HR: 0.32; CI95% 0.14-0.71). Conclusions: Despite the retrospective nature of the analysis and the low number of pts, we found a significant difference on mPFS and OS between S1 and S2 groups. In pts with advanced WD EP-NETs treated with PRRT plus SSA after SSA failure, the “switch” strategy of SSA after PD, might improve PFS and/or OS. Legal entity responsible for the study: Sara Pusceddu. Funding: Has not received any funding. Disclosure: N. Prinzi: Italfarmaco, Novartis: Consultancies. G. Lo Russo: AstraZeneca, BMS, MSD: Consultancies. S. Pusceddu: Novartis, Ipsen, Italfarmaco, Pfizer and advanced accelerator applications (AAA). All other authors have declared no conflicts of interest.