Although some reports have found increasing HLA disparity between donor and recipient to be associated with fewer relapses after allogeneic blood or marrow transplantation (BMT), this potential benefit has been offset by more graft-versus-host disease (GVHD) and nonrelapse mortality. However, the type of GVHD prophylaxis could influence the balance between GVHD toxicity and relapse. We analyzed the impact of greater HLA disparity on outcomes of a specific platform for nonmyeloablative, HLA-haploidentical transplantation. A retrospective analysis was performed on 185 patients with hematologic malignancies enrolled on three similar trials of nonmyeloablative, related donor, haploidentical BMT incorporating high-dose posttransplantation cyclophosphamide for GVHD prophylaxis. No significant association was found between the number of HLA mismatches (HLA-A, -B, -Cw, and -DRB1 combined) and risk of acute grade II–IV GVHD (hazard ratio .89, P = .68 for 3–4 versus fewer antigen mismatches). More mismatching also had no detrimental effect on event-free survival (on multivariate analysis, hazard ratio .60, P = .03 for 3–4 versus fewer antigen mismatches; hazard ratio .55, P = .03 for 3–4 versus fewer allele mismatches). Thus, greater HLA disparity does not appear to worsen overall outcomes after nonmyeloablative haploidentical BMT with high-dose posttransplantation cyclophosphamide.
PURPOSE The TAPUR Study is a phase II basket trial that aims to identify signals of antitumor activity of commercially available targeted agents in patients with advanced cancers harboring genomic alterations known to be drug targets. Results in a cohort of patients with metastatic breast cancer (mBC) with high tumor mutational burden (HTMB) treated with pembrolizumab are reported. METHODS Patients with advanced mBC received standard doses of either 2 mg/kg or 200 mg infusions of pembrolizumab every 3 weeks. Simon's two-stage design was used with a primary study end point of disease control (DC) defined as objective response or stable disease of at least 16 weeks duration. If two or more patients in stage I achieved DC, the cohort would enroll 18 additional patients in stage II. Secondary end points include progression-free survival (PFS), overall survival, and safety. RESULTS Twenty-eight patients were enrolled from October 2016 to July 2018. All patients' tumors had HTMB ranging from 9 to 37 mutations/megabase. DC and objective response were noted in 37% (95% CI, 21 to 50) and 21% of patients (95% CI, 8 to 41), respectively. Median PFS was 10.6 weeks (95% CI, 7.7 to 21.1); median overall survival was 30.6 weeks (95% CI, 18.3 to 103.3). No relationship was observed between PFS and tumor mutational burden. Five patients experienced ≥ 1 serious adverse event or grade 3 adverse event at least possibly related to pembrolizumab consistent with the product label. CONCLUSION Pembrolizumab monotherapy has antitumor activity in heavily pretreated patients with mBC characterized by HTMB. Our findings support the recent US Food and Drug Administration approval of pembrolizumab for treatment of patients with unresectable or metastatic solid tumors with HTMB without alternative treatment options.
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