The following article features coverage from the ASCO Gastrointestinal Cancers Symposium 2021 meeting. Click here to read more of Cancer Therapy Advisor‘s conference coverage.

Results from the phase 1b/2 PLANET study showed that lanreotide synergized with pembrolizumab to yield a stable disease rate of 40.9% in patients with advanced well- or moderately differentiated gastroenteropancreatic neuroendocrine tumors (GEP-NETs).

Data presented at the 2021 Gastrointestinal Cancers Symposium showed that, at a median follow-up of 15 months, the median progression-free survival (PFS) was 5.4 months with the combination therapy (95% CI, 2.7-8.3). The median overall survival (OS) had not been reached.

There were no partial or complete responses. Overall, 54.5% of patients had progressive disease; 4.5% were not evaluable for response assessment.

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The PLANET trial ( identifier: NCT03043664) included 22 patients with progressive, advanced or metastatic GEP-NETs who received lanreotide plus pembrolizumab. Six of these patients were treated in a safety cohort. The primary end point was overall response rate (ORR). Secondary end points included PFS, OS, and safety.

At baseline, the median patient age was 60.9 years and the median time since diagnosis was 5.3 years. The NET was located within the gastrointestinal track among 63.6% of patients, with the remaining 36.4% in the pancreas. The median Ki67 was 5%.

Data from previous studies have demonstrated an ORR of 3.7% to 12% with pembrolizumab in patients with low-grade NETs. Somatostatin analogues (SSAs) such as lanreotide can be an effective treatment for NETs and may modulate immunity through the reduction of serotonin. The aim of the PLANET study was to determine whether lanreotide and pembrolizumab would be synergetic in patients with low- to intermediate-grade GEP-NETs.

Regarding toxicities, no new safety signals were identified in the PLANET trial. Serious pembrolizumab-related adverse events occurred in 9 patients and included hyperglycemia, colitis, pneumonitis, and abdominal pain. Treatment discontinuation due to AEs occurred in 13.6% of patients. There were no grade 5 events.

“Further studies to identify other approaches to increase the immunogenicity of well/moderately-differentiated GEP-NETs are required,” concluded Michael Morse, MD, who presented the findings.

Disclosures: Some of the study authors disclosed financial relationships with the pharmaceutical industry and/or the medical device industry. For a full list of disclosures, please refer to the original study. This clinical trial was supported by Ipsen and Merck.

Read more of Cancer Therapy Advisor‘s coverage of the ASCO GI 2021 meeting by visiting the conference page.


Morse M, Halperin DM, Uronis HE, et al. Phase Ib/II study of pembrolizumab with lanreotide depot for advanced, progressive gastroenteropancreatic neuroendocrine tumors (PLANET). Presented at: Gastrointestinal Cancers Symposium; January 15-17, 2021. Abstract 369.