Background: There is uncertainty around clinical applicability of tumor mutational burden (TMB) across cancer types, in part because of inconsistency between TMB measurements from different platforms. The KEYNOTE 158 trial supported United States Food and Drug Administration (FDA) approval of the Foundation Medicine test (FoundationOneCDx) at TMB≥10 mut/Mb as a companion diagnostic (CDx) for single-agent pembrolizumab in second+line. Using a large real-world dataset with validated survival endpoint data, we evaluated clinical validity of TMB measurement by the test in over 8000 patients across 24 cancer types who received single-agent immune checkpoint inhibitor (ICI). Methods: Patients with advanced-stage cancers from 24 cancer types treated with single-agent anti-PD(L)1 therapy in standard-of-care settings were included. Deidentified data from electronic health records from approximately 280 cancer treatment facilities were captured into a clinico-genomic database. This study used the TMB algorithm from the FDA-approved test supporting solid tumor CDx and composite mortality variable validated against the national death index: real-world overall survival (rwOS). Following a prespecified analysis plan, rwOS by TMB level was assessed using Cox PH models adjusted for Eastern Cooperative Oncology Group performance status, prior treatment, microsatellite instability, sex, age, opioid rx pretherapy, and socioeconomic assessment. Results: 8440 patients met inclusion criteria. Adjusting for aforementioned factors, increasing TMB was significantly associated with rwOS across tumor types; HRs (95% CIs) relative to TMB<5: TMB 5 to <10: 0.95 (0.89 to 1.02), TMB 10 to <20: 0.79 (0.73 to 0.85), TMB≥20: 0.52 (0.47 to 0.58). For individual cancer types with prespecified statistical power, adjusted rwOS comparing TMB≥10 vs TMB8000 patients treated with single-agent ICI, and within individual cancer types with sufficient power, elevated TMB based on the FDA-approved CDx was associated with more favorable rwOS compared with similar patients with lower TMB levels. This biomarker deserves further clinical investigation to potentially guide the use of immunotherapy in expanded clinical contexts.

Purpose: Genomic rearrangements can generate potent oncogenic drivers or disrupt tumor suppressor genes. This study examines the landscape of fusions and rearrangements detected by liquid biopsy (LBx) of circulating tumor DNA (ctDNA) across different cancer types. Experimental Design: LBx from 53,842 patients with 66 solid tumor types were profiled using FoundationOneLiquid CDx, a hybrid-capture sequencing platform that queries 324 cancer-related genes. Tissue biopsies (TBx) profiled using FoundationOneCDx were used as a comparator. Results: Among all LBx, 7,377 (14%) had ≥1 pathogenic rearrangement detected. A total of 3,648 (6.8%) LBx had ≥1 gain-of-function (GOF) oncogene rearrangement, and 4,428 (8.2%) LBx had ≥1 loss-of-function rearrangement detected. Cancer types with higher prevalence of GOF rearrangements included those with canonical fusion drivers: prostate cancer (19%), cholangiocarcinoma (6.4%), bladder (5.5%), and non–small cell lung cancer (4.4%). Although the prevalence of driver rearrangements was lower in LBx than TBx overall, the frequency of detection was comparable in LBx with a tumor fraction (TF) ≥1%. Rearrangements in FGFR2, BRAF, RET, and ALK, were detected across cancer types, but tended to be clonal variants in some cancer types and potential acquired resistance variants in others. Conclusions: In contrast to some prior literature, this study reports detection of a wide variety of rearrangements in ctDNA. The prevalence of driver rearrangements in tissue and LBx was comparable when TF ≥1%. LBx presents a viable alternative when TBx is not available, and there may be less value in confirmatory testing when TF is sufficient.

Purpose: The purpose of the study was to compare the effectiveness of PARP inhibitor maintenance therapy (mPARPi) in real-world practice by biomarker status [BRCA1/2 alterations (BRCAalt) and a homologous recombination deficiency signature (HRDsig)] in advanced ovarian cancer. Experimental Design: Patients with ovarian cancer receiving first-line platinum-based chemotherapy and either mPARPi or no maintenance were included. Patient data were obtained by a US-based de-identified ovarian cancer Clinico-Genomic Database, from ∼280 US cancer clinics (01/2015–03/2023). Real-world progression-free survival (rwPFS) and overall survival (rwOS) were compared by biomarker status using Cox models, weighted by propensity scores. Results: Of 673 patients, 160 received mPARPi [31.2% BRCAalt and 51.9% HRDsig(+)] and 513 no maintenance [15.6% BRCAalt and 34.1% HRDsig(+)]. BRCAalt patients receiving mPARPi versus no maintenance had favorable rwPFS [HR, 0.48; 95% confidence interval (CI), 0.26–0.87; P = 0.0154], as did BRCA wild-type (WT; HR, 0.76; 95% CI, 0.57–1.01; P = 0.0595). Favorable rwOS was not observed with mPARPi for BRCAalt or BRCA-WT. HRDsig(+) patients receiving mPARPi versus no maintenance had favorable rwPFS (HR, 0.36; 95% CI, 0.24–0.55; P < 0.001) and numerically favorable rwOS (HR, 0.46; 95% CI, 0.21–1.02; P = 0.0561). No differences were observed for HRDsig(−). mPARPi treatment interaction was observed for HRDsig(+) versus HRDsig(−) (rwPFS P < 0.001/rwOS P = 0.016) but not for BRCAalt versus BRCA-WT. Patients with BRCA-WT/HRDsig(+) receiving mPARPi had favorable rwPFS (HR, 0.40; 95% CI, 0.22–0.72; P = 0.003), whereas no difference was observed for BRCA-WT/HRDsig(−). Conclusions: HRDsig predicted benefit of mPARPi better than BRCAalt. Patients with HRDsig(+) status experienced favorable outcomes, even if they had BRCA-WT status. In contrast, patients with HRDsig(−) status did not show significant benefit from mPARPi treatment. HRDsig might predict benefit from mPARPi regardless of BRCAalt status.

Objective Molecular profiling is developing to inform treatment in endometrial cancer. Using real world evidence, we sought to evaluate frontline immune checkpoint inhibitor vs chemotherapy effectiveness in advanced endometrial cancer, stratified by Tumor Mutational Burden (TMB) ≥10 mut/MB and microsatellite instability (MSI). Methods Patients with advanced endometrial cancer in the US-based de-identified Flatiron Health-Foundation Medicine Clinico-Genomic Database were included. Data originated from patients treated between January 2011- March 2022 at 280 US clinics. Next-generation sequencing assays were performed via FoundationOne or FoundationOneCDx. Longitudinal clinical data were derived from electronic health records. Immune checkpoint inhibitor treatment included pembrolizumab, dostarlimab, and nivolumab monotherapies. Time to next treatment, time to treatment discontinuation, and overall survival were assessed with the log-rank test and Cox proportional hazard models with adjusted hazard ratios (aHR) for known prognostic factors. We used the Likelihood ratio test to compare biomarker performance. Results A total of 343 patients received chemotherapy and 28 received immune checkpoint inhibitor monotherapy as frontline treatment. Patients who received monotherapy were more likely to be stage III at diagnosis (immune checkpoint inhibitor: 54.6% vs chemotherapy: 15.0%; p<0.001) and more likely to test MSI-high via next-generation sequencing (immune checkpoint inhibitor: 53.6% vs chemotherapy: 19.2%; p<0.001). In MSI-high cancers, single-agent immune checkpoint inhibitor had a more favorable time to next treatment (aHR: 0.18, p=0.001) and overall survival (aHR 0.29, p=0.045). Additional analyses on 70 unique tumor specimens revealed mismatch repair deficiency (dMMR) via immunohistochemistry and MSI-high via next-generation sequencing concordance (91%), with nominal improvement of MSI over dMMR to predict time to treatment discontinuation (p=0.030), time to next treatment (p=0.032), and overall survival (p=0.22). MSI status was concordant with tumor mutational burden ≥10 in 94.3% of cases. Conclusion Immune checkpoint inhibitors may have improved efficacy over chemotherapy in frontline treatment for advanced endometrial cancer defined by MSI-high using next-generation sequencing as a nominally better predictor of outcomes than dMMR with immunohistochemistry. This provides the biologic rationale of active phase III trials.