Somatostatin Analogs for Pancreatic Neuroendocrine Tumors: Any Benefit When Ki-67 Is ≥10%?

BACKGROUND: Long-acting somatostatin analogs (SSAs) are the primary first-line treatment of well-differentiated advanced gastroenteropancreatic neuroendocrine tumors (NETs), but data about their efficacy in pancreatic NETs (panNETs) with Ki-67 ≥10% are still limited.

MATERIALS AND METHODS: To assess the clinical outcomes of advanced, nonfunctioning, well-differentiated panNETs with Ki-67 ≥10% receiving first-line long-acting SSAs in a real-world setting, we carried out a retrospective, multicenter study including patients treated between 2014-2018 across 10 centers of the NET CONNECT Network. The primary endpoints were time to next treatment (TNT) and progression-free survival (PFS), whereas overall survival (OS) and treatment safety were secondary endpoints.

RESULTS: A total of 73 patients were included (68 grade [G]2, 5 G3), with liver metastases in 61 cases (84%). After a median follow-up of 36.4 months (range, 6-173), the median TNT and PFS were 14.2 months (95% confidence interval [CI], 11.6-16.2) and 11.9 months (95% CI, 8.6-14.1) respectively. No statistically significant difference was observed according to the somatostatin analog used (octreotide vs. lanreotide), whereas increased tumor grade (hazard ratio [HR], 4.4; 95% CI, 1.2-16.6; p = .04) and hepatic tumor load (HR, 2; 95% CI, 1-4; p = .03) were independently associated with shortened PFS. The median OS recorded was 86 months (95% CI, 56.8-86 months), with poor outcomes observed when the hepatic tumor burden was >25% (HR, 3.4; 95% CI, 1.2-10; p = .01). Treatment-related adverse events were reported in 14 patients, most frequently diarrhea.

CONCLUSION: SSAs exert antiproliferative activity in panNETs with Ki-67 ≥10%, particularly in G2 tumors, as well as when hepatic tumor load is ≤25%.

IMPLICATIONS FOR PRACTICE: The results of the study call into question the antiproliferative activity of somatostatin analogs (SSAs) in pancreatic neuroendocrine tumors with Ki-67 ≥10%. Patients with grade 2 tumors and with hepatic tumor load ≤25% appear to derive higher benefit from SSAs. Prospective studies are needed to validate these results to optimize tailored therapeutic strategies for this specific patient population.