Less frequent radiological exams to avoid futile response assessments from 177-LuDOTATE therapy for patients with advanced neuroendocrine tumors.

Background: 177-LuDOTATE is an effective but expensive treatment for neuroendocrine tumors (NETs). Reducing treatment-related costs, such as the number of images, could improve access to 177-LuDOTATE. We evaluated early radiological tumor progression and prognostic factors in patients with NETs treated with 177-LuDOTATE.

Methods: We retrospectively included all patients with NETs who received at least one cycle of 177-LuDOTATE. The primary endpoint was the rate of early radiological progression between cycles 2 and 3 (in 10-16 weeks). Secondary endpoints were progression-free survival (PFS) and overall survival (OS) according to prognostic factors (tumor grade, primary site, functioning syndrome, 177-LuDOTATE treatment line) in Cox proportional hazards models.

Results: The median number of 177-LuDOTATE cycles was 3 (range 1-6) among 59 patients included. Ten (17%) patients had early progression. Among 14 patients who received ≤2 cycles of 177-LuDOTATE, ten (72%) stopped treatment due to disease progression, with five patients having a G2 (ki67: 5-25%) and 4, a G3 (ki67: 25-90%) NET. In the Cox multivariable analysis, higher grade (G2 or G3 vs G1) were significantly associated with inferior PFS and OS. The median PFS of G1, G2 and G3 NET patients were: 34.1, 11.7 and 6.1 months (P = 0.015), respectively.

Conclusions: It is feasible to perform imaging tests after 177-LuDOTATE completion for patients with indolent NETs with the intent to avoid futile assessments. For patients with more aggressive diseases, such as G3 NETs and G2 tumors with high tumor burden, we advise to perform more frequent images during 177-LuDOTATE therapy.