In patients with well-differentiated neuroendocrine tumours, there is no apparent benefit of somatostatin analogues after disease control by peptide receptor radionuclide therapy

Abstract

Purpose: Peptide receptor radionuclide therapy (PRRT) and somatostatin analogues (SSAs) are commonly combined as primary treatment for neuroendocrine neoplasms (NEN), and SSAs given as maintenance. We sought to evaluate whether sequential therapy with PRRT followed by SSAs has progression or survival benefits in patients with NEN after disease control by PRRT.

Methods: This prospective, randomised, single-centre study had as principal eligibility criteria: unresectable, locally advanced, or metastatic, histologically confirmed well-differentiated NEN; no symptoms/biochemical diagnosis of carcinoid syndrome; no SSAs or ≤ 3 months of SSAs before PRRT; and stable disease or partial or complete response after PRRT. Altogether, 115 patients were randomised 2:1 to an SSA group (n = 74) given octreotide acetate LAR every 4 weeks, or a control group (n = 41) receiving only best supportive care. Octreotide treatment was to stop upon intolerable toxicity or patient refusal, or, at physician/patient discretion, upon NEN progression. The primary endpoint was progression-free survival (PFS), the secondary endpoint, and overall survival (OS).

Results: Median (25th-75th percentile) follow-up from the first PRRT activity to death or latest observation was 6.6 (3.18-10.22) years. During that time, 71/115 patients (62%) progressed, 52/74 (70%) in the SSA group, and 19/41 (46%) in the control group (p = 0.01). Eighty-eight/115 patients (76%) died, 58/74 (78%) in the SSA group, and 30/41 (73%) in the control group (p = 0.52). Median (95% CI) PFS was 4.7 (2.8-7.7) years in the SSA group, and 6.4 (4.1-not reached) years in controls. Overall, median OS was 6.6 years. Neither PFS nor OS differed between groups (p = 0.129, p = 0.985, respectively).

Conclusions: In patients with disease control after PRRT, subsequent SSA treatment appeared not to be associated with better PFS or OS. Whether to continue SSA administration upon progression after PRRT requires evaluation in a prospective, randomised, controlled multicentre study with a relatively homogeneous sample.

Keywords: Neuroendocrine malignancies; Peptide receptor radionuclide therapy; Sequential treatment; Somatostatin analogues; Survival.