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Pembrolizumab in Patients with Advanced Miscellaneous Rare Cancers: Results from a Phase 2 Basket Trial
Mirella Nardo1, Camila Braganca Xavier1, Bettzy Stephen1
1Department of Investigational Cancer Therapeutics, Division of Cancer Medicine, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
Introduction:
Rare solid tumors account for one-quarter of cancers among adults in the United States, but few resources have been devoted to their treatment. We evaluated the efficacy of pembrolizumab, a programmed cell death-1 inhibitor, in patients with rare solid tumors.
Methods:
We conducted a phase 2 basket trial that included patients with rare, advanced tumors. Patients were enrolled in the study in nine tumor-specific and a 10th cohort of miscellaneous rare histologies. Patients received pembrolizumab 200 mg intravenously every 21 days. The primary endpoint was the non-progression rate at 27 weeks per immune-related Response Evaluation Criteria in Solid Tumors (RECIST). The secondary endpoints were confirmed objective response (immune-related complete response [irCR] or partial response [irPR]), clinical benefit (irCR, irPR, or immune-related stable disease [irSD] ≥ 4 months), safety, and tolerability. Pretreatment biopsy specimens were examined for programmed cell death ligand-1 combined positive score (CPS) and tumor-infiltrating lymphocyte status. Herein, we report the outcomes in 12 patients with miscellaneous rare histologies who were on the study between October 5, 2016, and August 30, 2019.
Results:
Twelve patients with rare cancers were enrolled from October 5, 2016, to August 30, 2019. The patients received a median of four lines of therapy before enrollment. Three patients (25%) remained free of progression at 27 weeks, one patient (8%) had an objective response, and five patients (42%) received clinical benefit. Six patients (50%) experienced at least one adverse event, of whom five (42%) experienced immune-related adverse events. The only grade ≥ 3 adverse event was non-immune-related anemia. Among the seven patients with CPS ≥ 1, one had irPR and two had irSD as the best response. Among the six patients with a CPS of 3, one had irPR and two had irSD as the best response.
Conclusions:
Single-agent pembrolizumab showed modest efficacy and was well tolerated in patients with rare solid tumors (ClinicalTrials.gov Identifier: NCT02721732).
Insights
Pembrolizumab demonstrated modest efficacy in treating rare solid tumors, with 42% of patients experiencing clinical benefit. This programmed cell death-1 inhibitor was generally well-tolerated, showing promise for these difficult-to-treat cancers.
Area of Science:
- Oncology
- Immunotherapy
Background:
- Rare solid tumors represent a significant portion of adult cancers in the US.
- Limited treatment options and resources exist for rare solid tumors.
- Pembrolizumab is a programmed cell death-1 (PD-1) inhibitor investigated for its efficacy.
Purpose of the Study:
- To evaluate the efficacy and safety of pembrolizumab in patients with rare solid tumors.
- To assess the non-progression rate, objective response, and clinical benefit of pembrolizumab.
- To explore the correlation between PD-L1 expression and treatment outcomes.
Main Methods:
- A phase 2 basket trial was conducted including patients with rare, advanced tumors.
- Patients received pembrolizumab 200 mg intravenously every 21 days.
- Primary endpoint was non-progression rate at 27 weeks; secondary endpoints included response, benefit, and safety. Pretreatment biopsies assessed PD-L1 combined positive score (CPS) and tumor-infiltrating lymphocytes.
Main Results:
- Three out of 12 patients (25%) remained progression-free at 27 weeks.
- One patient (8%) achieved an objective response, and five patients (42%) experienced clinical benefit.
- 50% of patients experienced adverse events, with 42% experiencing immune-related adverse events. No grade ≥ 3 immune-related adverse events were observed.
Conclusions:
- Single-agent pembrolizumab showed modest efficacy in patients with rare solid tumors.
- Pembrolizumab was well-tolerated in this patient population.
- The study (ClinicalTrials.gov Identifier: NCT02721732) suggests potential for PD-1 inhibition in rare cancers.
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