Circulating Tumor DNA Assessment for Treatment Monitoring Adds Value to PSA in Metastatic Castration Resistant Prostate Cancer.

PURPOSE: Enzalutamide after abiraterone progression is commonly used in metastatic castration resistant prostate cancer (mCRPC) despite a low rate of clinical benefit. Analyzing IMbassador250, a phase III trial assessing enzalutamide with or without atezolizumab after abiraterone, we hypothesized that baseline and early changes in circulating tumor DNA (ctDNA) tumor fraction (TF) may identify patients more likely to exhibit survival benefit from enzalutamide. EXPERIMENTAL DESIGN: ctDNA was quantified from plasma samples using a tissue-agnostic assay without buffy coat sequencing. Baseline ctDNA TF, changes in ctDNA TF from baseline to cycle 3 day 1 (C3D1), and detection at C3D1 alone, were compared vs overall response rate (ORR), radiographic progression-free survival (rPFS), median OS (mOS), and 50% reduction in PSA. RESULTS: ctDNA TF detection at baseline and/or C3D1 was associated with shorter rPFS and OS in 494 evaluable patients. Detection of ctDNA TF at C3D1, with or without detection at C1D1, was associated with worse rPFS and mOS than lack of detection. When ctDNA TF and PSA response at C3D1 were discordant, patients with [ctDNA TF undetected/PSA not reduced] had more favorable outcomes than [ctDNA TF detected/PSA reduced] (mOS 22.1 months vs. 16 months, p<0.001). CONCLUSIONS: In a large cohort of mCRPC patients receiving enzalutamide after abiraterone, we demonstrate the utility of a new tissue-agnostic assay for monitoring molecular response based on ctDNA TF detection and dynamics. CtDNA TF provides a minimally-invasive, complementary biomarker to PSA testing and may refine personalized treatment approaches.

Comprehensive genomic profiling of ESR1, PIK3CA, AKT1, and PTEN in HR(+)HER2(-) metastatic breast cancer: prevalence along treatment course and predictive value for endocrine therapy resistance in real-world practice.

BACKGROUND: The treatment landscape for HR(+)HER2(-) metastatic breast cancer (MBC) is evolving for patients with ESR1 mutations (mut) and PI3K/AKT pathway genomic alterations (GA). We sought to inform clinical utility for comprehensive genomic profiling (CGP) using tissue (TBx) and liquid biopsies (LBx) in HR(+)HER2(-) MBC. METHODS: Records from a de-identified breast cancer clinicogenomic database for patients who underwent TBx/LBx testing at Foundation Medicine during routine clinical care at ~ 280 US cancer clinics between 01/2011 and 09/2023 were assessed. GA prevalence [ESR1mut, PIK3CAmut, AKT1mut, PTENmut, and PTEN homozygous copy loss (PTENloss)] were calculated in TBx and LBx [stratified by ctDNA tumor fraction (TF)] during the first three lines of therapy. Real-world progression-free survival (rwPFS) and overall survival (rwOS) were compared between groups by Cox models adjusted for prognostic factors. RESULTS: ~ 60% of cases harbored 1 + GA in 1st-line TBx (1266/2154) or LBx TF ≥ 1% (80/126) and 26.5% (43/162) in LBx TF < 1%. ESR1mut was found in 8.1% TBx, 17.5% LBx TF ≥ 1%, and 4.9% LBx TF < 1% in 1st line, increasing to 59% in 3rd line (LBx TF ≥ 1%). PTENloss was detected at higher rates in TBx (4.3%) than LBx (1% in TF ≥ 1%). Patients receiving 1st-line aromatase inhibitor + CDK4/6 inhibitor (n = 573) with ESR1mut had less favorable rwPFS and rwOS versus ESR1 wild-type; no differences were observed for fulvestrant + CDK4/6 inhibitor (n = 348). CONCLUSION: Our study suggests obtaining TBx for CGP at time of de novo/recurrent diagnosis, followed by LBx for detecting acquired GA in 2nd + lines. Reflex TBx should be considered when ctDNA TF < 1%.

Predictive Impact of Tumor Mutational Burden on Real-World Outcomes of First-Line Immune Checkpoint Inhibition in Metastatic Melanoma.

PURPOSE: The choice of threshold and reliability of high tumor mutational burden (TMB) to predict outcomes and guide treatment choice for patients with metastatic melanoma receiving first-line immune checkpoint inhibitor (ICI) therapy in the real world is not well known. METHODS: Using a deidentified nationwide (US-based) melanoma clinicogenomic database, we identified a real-world cohort of patients with metastatic melanoma (N = 497) who received first-line monotherapy anti-PD-1 (n = 240) or dual anti-PD-1 and anti-CTLA-4 ICI (n = 257) and had a tissue-based comprehensive genomic profiling test TMB score. RESULTS: TMB-high (TMB-H; ≥10 mutations per megabase [muts/Mb], n = 352, 71%) was independently predictive of superior real-world progression-free survival and overall survival versus TMB-low (<10 mut/Mb, n = 145, 29%) in both mono ICI (hazard ratio [HR], 0.45 [95% CI, 0.32 to 0.63]; P < .001; HR, 0.61 [95% CI, 0.41 to 0.90]; P = .01, respectively) and dual ICI (HR, 0.67 [95% CI, 0.49 to 0.90]; P = .009; HR, 0.61 [95% CI, 0.42 to 0.88]; P = .007, respectively) patients. Dual ICI offered no significant advantage in BRAFwt patients and unexpectedly demonstrated greatest benefit in the TMB 10-19 mut/Mb group, identifying a TMB-very high (≥20 mut/Mb, n = 247, 50%) BRAFmut patient subgroup for whom mono ICI may be preferable. CONCLUSION: TMB-H predicts superior outcomes on ICI while coassessment of BRAF status and TMB may inform first-line regimen choice.

Measurement of ctDNA Tumor Fraction Identifies Informative Negative Liquid Biopsy Results and Informs Value of Tissue Confirmation.

PURPOSE: Liquid biopsy (LBx) for tumor profiling is increasingly used, but concerns remain regarding negative results. A lack of results may truly reflect tumor genomics, or it may be a false negative that would be clarified by tissue testing. A method of distinguishing between these scenarios could help clarify when follow-on tissue testing is valuable. EXPERIMENTAL DESIGN: Here we evaluate circulating tumor DNA (ctDNA) tumor fraction (TF), a quantification of ctDNA in LBx samples, for utility in identifying true negative results. We assessed concordance between LBx and tissue-based results, stratified by ctDNA TF, in a real-world genomic dataset of paired samples across multiple disease types. We also evaluated the frequency of tissue results identifying driver alterations in patients with lung cancer after negative LBx in a real-world clinicogenomic database. RESULTS: The positive percent agreement and negative predictive value between liquid and tissue samples for driver alterations increased from 63% and 66% for all samples to 98% and 97% in samples with ctDNA TF ≥1%. Among 505 patients with lung cancer with no targetable driver alterations found by LBx who had subsequent tissue-based profiling, 37% had a driver, all of which had ctDNA TF <1%. CONCLUSIONS: Patients with lung cancer with negative LBx and ctDNA TF ≥1% are unlikely to have a driver detected on confirmatory tissue testing; such informative negative results may benefit instead from prompt treatment initiation. Conversely, negative LBx with ctDNA TF <1% will commonly have a driver identified by follow-up tissue testing and should be prioritized for reflex testing.

Circulating Tumor DNA Enables Sensitive Detection of Actionable Gene Fusions and Rearrangements Across Cancer Types.

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.

Genomic Profiles and Clinical Outcomes of Penile Squamous Cell Carcinoma With Elevated Tumor Mutational Burden.

Importance: Tumor mutational burden (TMB) is a putative biomarker of efficacy for immune checkpoint inhibitor (ICI) therapies of solid tumors, but not specifically for penile squamous cell carcinoma (PSCC). Objective: To characterize biomarker features and ICI therapy outcomes associated with high TMB in PSCC in the routine clinical practice setting. Design, Setting, and Participants: In this cohort study, 397 PSCC cases were analyzed to identify genomic alterations in more than 300 cancer-associated genes and genomic signatures, including TMB, using a hybrid capture-based comprehensive genomic profiling assay. Tumor mutational burden was categorized as low (<10 mutations per megabase [mut/Mb]), high (10-19 mut/Mb), or very high (≥20 mut/Mb). Germline status of genetic alterations was predicted using a validated somatic-germline computational method. Clinical outcomes of patients with metastatic PSCC receiving first-line ICI were abstracted using the deidentified nationwide Clinico-Genomic Database (CGDB) from January 1, 2011, through December 31, 2022. Exposure: Comprehensive genomic profiling was performed using FoundationOne and FoundationOne CDx assays from Foundation Medicine Inc. Main outcomes and measures: The spectrum of genetic alterations by TMB level in PSCC, the percentage of germline genetic alterations, and the outcome (overall survival with routine clinical treatment) by TMB of chemotherapy-naive patients with PSCC who received ICI treatment up front were assessed in this descriptive study. Results: Among 397 patients (median [IQR] age, 65 [54-73] years; 266 [67.0%] of European, 83 [20.9%] of admixed American, and 34 [8.5%] of African or other genomic ancestry), the median (IQR) age (eg, 65 [53-73] years for low TMB vs 68 [61-78] years for TMB ≥10 mut/Mb) and genomic ancestry distribution (eg, European 228 of 339 [67.3%] for low TMB vs 38 of 58 [65.5%] for TMB ≥10 mut/Mb) were similar between TMB subgroups. There were 339 PSCC cases (85.4%) with low TMB, 40 cases (10.1%) with high TMB, and 18 cases (4.5%) with very high TMB. Comparisons of TMB of 10 mut/Mb or higher vs low TMB showed an enrichment of genetic alterations in PIK3CA (48.3% vs 18.3%; P < .001) and KMT2D (29.3% vs 7.7%; P < .001) and less frequent genetic alterations in CDKN2A (25.9% vs 45.7%; P = .05). Most genetic alterations did not co-occur. Human papillomavirus identification was more frequent as TMB increased: 28.3% for low TMB, 50.0% for high, and 72.2% for very high. In total, 95 of 1377 genetic alterations (6.9%) were germline. Of 10 patients identified from the CGDB receiving frontline ICIs, median (IQR) follow-up was 9.9 months. Four patients had overall survival with clinical treatment of more than 12 months, including 2 of 3 patients with TMB of 10 mut/Mb or higher. Conclusions and Relevance: In this cohort study of advanced metastatic PSCC based on TMB levels, significant differences were observed for biomarkers in nearly 15% of patients with a TMB of 10 mut/Mb or higher. Germline testing and ICI-based therapy should be integrated into the management of selected PSCC cases.

Clinical and Genomic Factors Associated with Greater Tumor Mutational Burden in Prostate Cancer.

Tumor mutational burden (TMB) is a biomarker that predicts response to immune checkpoint inhibitor therapy. We currently lack a comprehensive understanding of how genomic and clinical factors correlate with TMB. We used a clinicogenomic database to assess independent predictors of TMB levels. The study included 2740 prostate cancer specimens from prostate gland (51.6%), lymph nodes (14.6%), and bone (10.4%). Androgen deprivation therapy use beyond 24 mo was weakly associated with high TMB (fold-change estimate [FCE] 1.14, 95% confidence interval [CI] 1.03-1.26; p = 0.009). In comparison to the prostate gland, metastases in the bladder (FCE 1.20, 95% CI 1.02-1.42; p = 0.029), liver (FCE 1.26, 95% CI 1.10-1.43; p < 0.001), and other locations (FCE 1.26, 95% CI 1.11-1.43; p < 0.001) were associated with high TMB. Microsatellite instability high (FCE 8.46, 95% CI 6.42-11.15; p < 0.001) and intermediate (FCE 1.77, 95% CI 1.46-2.14; p < 0.001) status were associated with greater TMB. Altered genes associated with greater TMB included MLH1 (FCE 1.81; p = 0.004), MSH2 (FCE 1.87; p < 0.001), MSH6 (FCE 1.92; p < 0.001), BRCA2 (FCE 1.69; p < 0.001), CDK12 (FCE 1.40; p < 0.001), MRE11 (FCE 2.28; p = 0.016), and PALB2 (FCE 2.08; p < 0.001). Our study demonstrates that TMB is relatively stable over lines of therapies and can be used to guide treatment at diagnosis or in later lines for patients with metastatic prostate cancer. Patient summary: The number of genetic mutations in a tumor (tumor mutational burden, TMB) may help in predicting a patient's response to immunotherapy in advanced prostate cancer. We evaluated clinical and genetic factors that may affect TMB. We found that metastases in the bladder and liver are more likely to have high TMB than the primary tumor. Some individual genes are associated with high TMB. No prior treatment type was strongly associated with TMB, suggesting that TMB can be used to guide treatment at any time point.These data were presented at the American Society of Clinical Oncology 2023 Genitourinary Cancers Symposium.

Tumor Mutational Burden in Real-World Patients With Pancreatic Cancer: Genomic Alterations and Predictive Value for Immune Checkpoint Inhibitor Effectiveness.

PURPOSE: Pancreatic ductal adenocarcinoma (PDAC) is largely considered a nonimmunogenic malignancy; however, approximately 1%, of patients may have tumors with deficient mismatch repair, high microsatellite instability, or high tumor mutational burden (TMB ≥10 mutations/Mb), which may be predictive of response to immune checkpoint inhibitor (ICI) therapy. We sought to analyze outcomes of patients with high-TMB and pathogenic genomic alterations observed in this population. METHODS: This study included patients with PDAC who underwent comprehensive genomic profiling (CGP) at Foundation Medicine (Cambridge, MA). Clinical data were obtained from a US-wide real-world clinicogenomic pancreatic database. We report genomic alterations in those with high and low TMB, and compare outcomes on the basis of receipt of single-agent ICI or therapy regimens not containing ICI. RESULTS: We evaluated 21,932 patients with PDAC who had tissue CGP data available, including 21,639 (98.7%) with low-TMB and 293 (1.3%) with high-TMB. Among patients with high-TMB, a greater number of alterations were observed in BRCA2, BRAF, PALB2, and genes of the mismatch repair pathway, whereas fewer alterations were observed in KRAS. Among patients who received an ICI (n = 51), those with high-TMB had more favorable median overall survival when compared with the low-TMB subset (25.7 v 5.2 months; hazard ratio, 0.32; 95% CI, 0.11 to 0.91; P = .034). CONCLUSION: Longer survival was observed in patients with high-TMB receiving ICI compared with those with low-TMB. This supports the role of high-TMB as a predictive biomarker for efficacy of ICI therapy in PDAC. Additionally, we report higher rates of BRAF and BRCA2 mutations and lower rates of KRAS mutation among patients with PDAC and high-TMB, which to our knowledge, is a novel finding.

Not all TMB assays are the same: Clinical validity of robust algorithmic germline filtering.

Huang et al. propose that a tumor-only calculation of tumor mutational burden (TMB), which leverages algorithmic filtering of germline variants, maintains clinical validity across ancestries without necessitating germline sequencing.

Variable Landscape of PD-L1 Expression in Breast Carcinoma as Detected by the DAKO 22C3 Immunohistochemistry Assay.

BACKGROUND: In 2020, pembrolizumab was approved as a therapy for triple-negative breast cancer (TNBC) with the companion diagnostic DAKO 22C3 programmed death ligand-1 (PD-L1) immunohistochemistry assay. The study aimed to determine the landscape of PD-L1 expression as detected by the DAKO 22C3 PD-L1 assay in breast cancer subtypes and compare the clinicopathologic and genomic characteristics of PD-L1 positive and negative TNBC. METHODS: PD-L1 expression using the DAKO 22C3 antibody was scored using a combined positive score (CPS) and positive status was defined as CPS ≥10. Comprehensive genomic profiling was performed using the FoundationOne CDx assay. RESULTS: Of the 396 BC patients stained with DAKO 22C3, the majority were HR+/HER2- and TNBC (42% and 36%, respectively). Median PD-L1 expression and frequency of CPS ≥10 was highest in TNBC cases (median: 7.5, 50% CPS ≥10) and lowest in the HR+/HER2- group (median: 1.0, 15.5% CPS ≥10) (P < .0001). A comparison of PD-L1 positive and PD-L1 negative TNBC demonstrated no significant differences in clinicopathologic or genomic characteristics. TNBC tissue samples from the breast did have an observed enrichment for PD-L1 positivity compared to TNBC tissue samples from a metastatic site (57% vs. 44%), but this was not statistically significant (P = .1766). In the HR+/HER2- group, genomic alterations in TP53, CREBBP, and CCNE1 were more prevalent and genomic loss of heterozygosity was higher in the PD-L1(+) group compared to the PD-L1(-) group. CONCLUSIONS: The subtypes of breast cancer have distinct patterns of PD-L1 expression, supporting that further research of immunotherapies may include specific evaluation of optimum cutoffs for non-TNBC patients. In TNBC, PD-L1 positivity is not associated with other clinicopathologic or genomic features and should be integrated into future studies of immunotherapy efficacy.

Mismatch repair deficiency, next-generation sequencing-based microsatellite instability, and tumor mutational burden as predictive biomarkers for immune checkpoint inhibitor effectiveness in frontline treatment of advanced stage endometrial cancer.

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.

BRAF V600E and RNF43 Co-mutations Predict Patient Outcomes With Targeted Therapies in Real-World Cases of Colorectal Cancer.

Anti-BRAF/EGFR therapy is approved for metastatic colorectal cancer (mCRC) with BRAFV600E mutations, although not all patients respond. Novel recent findings indicate the potential of RNF43 mutations to predict outcomes in patients with BRAF-mutated microsatellite stable (MSS) mCRC treated with anti-BRAF/EGFR therapy. This study aimed to independently and rapidly validate BRAFV600E/RNF43 co-mutations as predictive biomarkers of benefit to anti-EGFR/BRAF therapy. Clinical data were derived from electronic health record data from ~280 US cancer clinics between January 2011 and March 2022 from the Flatiron Health-Foundation Medicine real-world clinico-genomic mCRC database. Real-world cases of BRAFV600E-mutated mCRC, with patients receiving anti-BRAF/EGFR therapy (n = 49), were included. Patients who were MSS, with RNF43 mutations, had favorable progression-free survival (hazard ratio [HR] 0.29; 95% CI [CI], 0.13-0.65) and overall survival (HR 0.32, 95% CI, 0.12-0.84) compared with wild type. No difference in outcomes was observed between patient groups with RNF43-mutant versus wild-type receiving standard-of-care chemotherapy. BRAFV600E/RNF43 co-mutations predict mCRC anti-BRAF/EGFR outcomes in diverse clinical settings.

Durable responders in advanced NSCLC with elevated TMB and treated with 1L immune checkpoint inhibitor: a real-world outcomes analysis.

BACKGROUND: For patients with advanced non-small cell lung carcinoma (NSCLC), immune checkpoint inhibitor (ICPI) and chemotherapy (chemo) ICPI represent two distinct first-line standard-of-care regimens without clear and established biomarkers to inform the optimal choice for individual patients. Here, we examined the complementary roles of tumor mutational burden (TMB) and programmed death ligand-1 (PD-L1) immunohistochemistry (IHC) to inform first-line therapy using a large real-world (rw) data set. MATERIALS AND METHODS: The study included patients with NSCLC from an rw de-identified clinico-genomic database. All patients underwent genomic testing using Foundation Medicine's tissue comprehensive genomic profiling assay and PD-L1 IHC assay scored for tumor cell staining (TS). RESULTS: Of 2165 patients included in the analysis, 150 exhibited durable benefit from first-line ICPI regimens (these patients were enriched for PD-L1 TS ≥50, non-squamous histology, and TMB ≥20 mutations/megabase (muts/Mb)). Comparing low TMB (<10 muts/Mb), high TMB (10-19 muts/Mb), and very high TMB (≥20 muts/Mb) receiving ICPI alone, we observed a stepwise increase in median rwPFS (real world-progression free survival) (6.5, 7.5, 17.2 months) and rwOS (real world-overall survival) (10.1, 11.8, 26.9 months) as TMB increased. In the low PD-L1 (TS <50%) cohort, TMB <20 muts/Mb showed a more favorable rwPFS (HR: 0.56 (95% CI: 0.40 to 0.79)) and rwOS (HR 0.74 (95% CI: 0.58 to 0.96)) on chemoICPI when compared with ICPI alone while the point estimate in rwPFS favored monoICPI in the TMB ≥20 muts/Mb cohort, the CI is wide and does not reach statistical significance (HR: 1.68 (95% CI: 0.52 to 5.48)). CONCLUSION: This study provides evidence that higher TMB cut-offs, such as 20 muts/Mb, can identify patients with prolonged benefit from ICPI. TMB ≥20 muts/Mb is a potential biomarker that may identify patients in whom an ICPI without chemo could be considered, even in the setting of lower PD-L1 levels. Prospective validation of these findings could increase access to chemo-sparing regimens for the first-line treatment of advanced NSCLC.

Comparative Effectiveness of Immune Checkpoint Inhibitors vs Chemotherapy in Patients With Metastatic Colorectal Cancer With Measures of Microsatellite Instability, Mismatch Repair, or Tumor Mutational Burden.

Importance: The KEYNOTE-177 trial demonstrated that patients with metastatic colorectal cancer (MCRC) with high microsatellite instability (MSI-H) and/or mismatch repair deficiency (DMMR) have better outcomes when receiving first-line immune checkpoint inhibitors (ICIs) compared with chemotherapy. Data on performance of ICIs in patients with MCRC in standard practice settings remain limited, and direct MMR vs MSI outcome association comparisons are lacking. Objective: To validate MSI (determined by next-generation sequencing [NGS]) as a biomarker of ICI effectiveness among patients with MCRC in standard practice settings and examine the association of MSI assessed by NGS, DMMR by immunohistochemistry, and tumor mutational burden (cutoff, 10 mutations/megabase) with ICI outcomes. Design, Setting, and Participants: This comparative effectiveness research study of outcomes in prospectively defined biomarker subgroups used data from a deidentified clinicogenomic database and included patients who received Foundation Medicine testing (FoundationOne or FoundationOne CDx) during routine clinical care at approximately 280 US academic or community-based cancer clinics between March 2014 and December 2021. The population included 1 cohort of patients with MSI-H MCRC who received first-line ICIs or chemotherapy and a second cohort who received ICIs in any line of therapy (LOT) for biomarker examination. Exposures: ICI therapy or chemotherapy assigned at physician discretion without randomization. Main Outcomes and Measures: The main outcomes were time to next treatment (TTNT), progression-free survival (PFS), and overall survival (OS). Hazard ratios were adjusted for known prognostic imbalances. Comparisons of explanatory power used the likelihood ratio test. Results: A total of 138 patients (median age, 67.0 years [IQR, 56.2-74.0 years]; 73 [52.9%] female) with MSI-H MCRC received first-line ICIs or chemotherapy. A total of 182 patients (median age, 64.5 years [IQR, 55.2-72.0]; 98 [53.8%] female) received ICIs in any LOT. Patients receiving first-line ICIs vs chemotherapy had longer TTNT (median, not reached [NR] vs 7.23 months [IQR, 6.21-9.72 months]; adjusted hazard ratio [AHR], 0.17; 95% CI, 0.08-0.35; P < .001), PFS (median, 24.87 months [IQR, 19.10 months to NR] vs 5.65 months [IQR, 4.70-8.34 months]; AHR, 0.31; 95% CI, 0.18-0.52; P < .001), and OS (median, NR vs 24.1 months [IQR, 13.90 months to NR]; HR, 0.45; 95% CI, 0.23-0.88; P = .02). MSI added to DMMR better anticipated TTNT and PFS in patients receiving ICIs than DMMR alone. The same was not observed when DMMR evaluation was added to MSI. Conclusions and Relevance: In this comparative effectiveness research study, MSI assessed by NGS robustly identified patients with favorable outcomes on first-line ICIs vs chemotherapy and appeared to better anticipate ICI outcomes compared with DMMR.

Biology and Targetability of the Extended Spectrum of PIK3CA Mutations Detected in Breast Carcinoma.

PURPOSE: Alpelisib is a PI3K alpha (PI3Kα)-selective inhibitor approved for the treatment of hormone receptor-positive/HER2-negative (HR+/HER2-) PIK3CA-mutated advanced breast cancer (ABC) based on the SOLAR-1 trial, which defined 11 substitutions in exons 7, 9, and 20 in PIK3CA (SOLAR1m). We report alpelisib effectiveness for ABC harboring SOLAR1m, as well as other pathogenic PIK3CA mutations (OTHERm) using comprehensive genomic profiling (CGP). EXPERIMENTAL DESIGN: A total of 33,977 tissue and 1,587 liquid biopsies were analyzed using hybrid capture-based CGP covering the entire coding sequence of PIK3CA. Clinical characteristics and treatment history were available for 10,750 patients with ABC in the deidentified Flatiron Health-Foundation Medicine clinico-genomic database (FH-FMI CGDB). RESULTS: PIK3CAm were detected in 11,767/33,977 (35%) of tissue biopsies, including 2,300 (7%) samples with OTHERm and no SOLAR1m. Liquid biopsy had 77% sensitivity detecting PIK3CAm, increasing to 95% with circulating tumor DNA fraction ≥2%. In patients with HR+/HER2- ABC and PIK3CAm receiving alpelisib/fulvestrant (ALP+FUL; n = 182) or fulvestrant alone (FUL; n = 119), median real-world progression-free survival (rwPFS) was 5.9 months on ALP+FUL [95% confidence interval (CI): 5.1-7.4] versus 3.1 months on FUL (95% CI: 2.7-3.7; P < 0.0001). In patients with OTHERm, median rwPFS was 4.0 months on ALP+FUL (95% CI: 2.8-10.1) versus 2.5 months on FUL (95% CI: 2.2-3.7; P = 0.0054). CONCLUSIONS: CGP detects diverse PIK3CAm in a greater number of patients with ABC than PCR hotspot testing; 20% of patients with PIK3CAm do not have SOLAR1m. These patients may derive benefit from alpelisib. See related commentary by Tau and Miller, p. 989.

Comparison of PD-L1 tumor cell expression with 22C3, 28-8, and SP142 IHC assays across multiple tumor types.

BACKGROUND: Multiple PD-L1 immunohistochemistry (IHC) assays, including DAKO 22C3, DAKO 28-8, and Ventana SP142 PD-L1 IHC assays, have been approved by the Food and Drug Administration as a companion diagnostic (CDx) for various antiprogrammed death-1 and antiprogrammed death ligand 1 (PD-L1) based cancer immunotherapies. Here we present 22C3, 28-8, and SP142 analysis of 418 tumor specimens encountered in routine clinical practice. METHODS: All specimens were tested with 22C3, 28-8, and SP142 assays following the manufacturer's established staining protocols. RESULTS: The same PD-L1 status (defined as tumor cell expression (TC) scores with all three assays ≥1% or all <1%) was observed in 60.0% (251/418) tumor specimens (45.9% (192/418) were triple negative and 14.1% (59/418) were triple positive). A total of 54.1% (226/418) tumor cases were positive with at least one IHC assay (94.2% (213/226), 77.0% (174/226), and 28.8% (65/226) of these were positive for 22C3, 28-8 and SP142, respectively). Among the 40.0% (167/418) tumor cases that showed a different PD-L1 status, 62.3% (104/167) were 22C3+/28-8+/SP142-, and 28.7% (48/167) were 22C3+/28-8-/SP142-. The same PD-L1 status with all three antibody clones was observed in 48.7% (97/199) of NSCLC cases, and among these, 54.6% (53/97) were triple negative and 45.4% (44/97) triple positive. A total of 73.4% (146/199) NSCLC cases were positive with at least one IHC assay (95.2% (n=139/146), 82.2% (n=120/146), and 32.2% (n=47/146) were positive for 22C3, 28-8, and SP142, respectively). Among the 51.3% (102/199) NSCLC cases that showed a different status among the three IHC assays, 67.6% (69/102) were 22C3+/28-8+/SP142-, and 23.5% (24/102) were 22C3+/28-8-/SP142-. A total of 81.1% (43/53) lung squamous cell carcinoma, 72.1% (88/122) of lung adenocarcinoma, 69.6% (16/23) of non-small cell lung cancer (NSCLC) not otherwise specified (NOS), and 50.0% (4/8) of small cell lung carcinoma cases were positive with at least one IHC assay. CONCLUSIONS: Our data suggest that 22C3 is the most sensitive PD-L1 IHC assay for tumor cell expression, followed by 28-8 and in turn by SP-142. These findings represent an additional factor for clinical teams to consider when deciding which PD-L1 IHC assay (and in turn which CDx-associated PD-L1 based immunotherapy) is most appropriate for each individual patient.

Real-World Comprehensive Genomic Profiling Success Rates in Tissue and Liquid Prostate Carcinoma Specimens.

Challenges with sequencing tissue samples from patients with prostate cancer have been reported in clinical trials. To assess the success rate of comprehensive genomic profiling (CGP) for prostate cancer patients, we analyzed a real-world cohort who underwent sequencing of their prostate tissue sample as well as a subset of patients with a reflex liquid biopsy. Overall, a significant majority (82%) of tissue prostate carcinoma samples yielded reportable CGP results. Of those samples that were unsuccessful, most (75%) were inadequate samples that did not meet pre-established criteria to advance into sequencing. For cases where liquid CGP was performed if tissue CGP was unsuccessful, mutations that were likely attributable to prostate carcinoma were observed in most cases and all cases were successful in generating a report. These results suggest that, for CGP testing, prostate cancer tissue is a reasonable matrix type and that liquid samples can be effectively used as an alternative to tissue.

SPOP Mutations as a Predictive Biomarker for Androgen Receptor Axis-Targeted Therapy in De Novo Metastatic Castration-Sensitive Prostate Cancer.

PURPOSE: Intensification of androgen deprivation therapy (ADT) with either docetaxel or androgen receptor axis-targeted therapies (ARAT) are the current standard of care for patients with metastatic castration-sensitive prostate cancer (mCSPC). However, biomarkers guiding treatment selection are lacking. We hypothesized that ADT intensification with ARAT, but not with docetaxel, would be associated with improved outcomes in patients with de novo (dn)-mCSPC harboring SPOP mutations. EXPERIMENTAL DESIGN: Patient-level data from a deidentified nationwide (U.S.-based) prostate cancer clinico-genomic database between January 2011 and December 2021 were extracted. Eligibility criteria: diagnosis of metastatic disease within 30 days of original prostate cancer diagnosis, genomic profiling of a tissue biopsy collected within 90 days of original diagnosis, and initiation of ARAT or docetaxel within 120 days of initial diagnosis. The log-rank test and Cox proportional hazards models were used to compare time to castration-resistant prostate cancer (TTCRPC) and overall survival (OS) for patients with and without SPOP mutations undergoing ADT intensification with ARAT or docetaxel. RESULTS: In the ARAT cohort, presence of SPOP mutation compared with wild-type was associated with more favorable TTCRPC [not reached (NR) vs. 16.7 months; adjusted HR (aHR), 0.20; 95% confidence interval (CI), 0.06-0.63; P = 0.006] and OS (NR vs. 27.2 months; aHR, 0.19; 95% CI, 0.05-0.79; P = 0.022). In contrast, SPOP mutation status was not associated with TTCRPC or OS in docetaxel-treated cohort. CONCLUSIONS: In real-world settings, SPOP mutations were associated with improved outcomes to ADT plus ARAT (but not ADT plus docetaxel) in patients with dn-mCSPC. This may serve as a predictive biomarker to guide treatment selection for patients with mCSPC.

Complementary Roles for Tissue- and Blood-Based Comprehensive Genomic Profiling for Detection of Actionable Driver Alterations in Advanced NSCLC.

Introduction: Whereas tumor biopsy is the reference standard for genomic profiling of advanced NSCLC, there are now multiple assays approved by the Food and Drug Administration for liquid biopsy testing of circulating tumor DNA. Here, we study the incremental value that liquid biopsy comprehensive genomic profiling (CGP) adds to tissue molecular testing. Methods: Patients with metastatic NSCLC were enrolled in a prospective diagnostic study to receive circulating tumor DNA CGP; tissue CGP was optional in addition to their standard tissue testing. Focusing on nine genes listed per the National Comprehensive Cancer Network (NCCN) guidelines, liquid CGP was compared with available tissue testing results across three subcohorts: tissue CGP, standard-of-care testing of up to five biomarkers, or no tissue testing. Results: A total of 515 patients with advanced nonsquamous NSCLC received liquid CGP. Among 131 with tissue CGP results, NCCN biomarkers were detected in 86 (66%) with tissue CGP and 56 (43%) with liquid CGP (p < 0.001). Adding liquid CGP to tissue CGP detected no additional patients with NCCN biomarkers, whereas tissue CGP detected NCCN biomarkers in 30 patients (23%) missed by liquid CGP. Studying 264 patients receiving tissue testing of up to five genes, 102 (39%) had NCCN biomarkers detected in tissue, with an additional 48 (18%) detected using liquid CGP, including 18 with RET, MET, or ERBB2 drivers not studied in tissue. Conclusions: For the detection of patients with advanced nonsquamous NSCLC harboring 9 NCCN biomarkers, liquid CGP increases detection in patients with limited tissue results, but does not increase detection in patients with tissue CGP results available. In contrast, tissue CGP can add meaningfully to liquid CGP for detection of NCCN biomarkers and should be considered as a follow-up when an oncogenic driver is not identified by liquid biopsy.

Tumor Mutational Burden as a Predictor of First-Line Immune Checkpoint Inhibitor Versus Carboplatin Benefit in Cisplatin-Unfit Patients With Urothelial Carcinoma.

PURPOSE: In real-world settings, patients with metastatic urothelial carcinoma (mUC) are often more frail than clinical trials, underscoring an unmet need to identify patients who might be spared first-line chemotherapy. We sought to determine whether tumor mutational burden (TMB) identifies patients with comparable or superior clinical benefit of first-line single-agent immune checkpoint inhibitors (ICPI) in real-world patients deemed cisplatin-unfit. METHODS: Patients with mUC treated in first-line advanced setting (N = 401) received ICPI (n = 245) or carboplatin regiment without ICPI (n = 156) at physician's discretion in standard-of-care settings across approximately 280 US academic or community-based cancer clinics between March 2014 and July 2021. Deidentified data were captured into a real-world clinicogenomic database. All patients underwent testing using Foundation Medicine assays. Progression-free survival (PFS), time to next treatment (TTNT), and overall survival (OS) comparing ICPI versus chemotherapy were adjusted for known treatment assignment imbalances using propensity scores. RESULTS: TMB ≥ 10 was detected in 122 of 401 (30.4%) patients. Among patients receiving ICPI, those with TMB ≥ 10 had more favorable PFS (HR, 0.59; 95% CI, 0.41 to 0.85), TTNT (HR, 0.59; 95% CI, 0.43 to 0.83), and OS (HR, 0.47; 95% CI, 0.32 to 0.68). Comparing ICPI versus carboplatin, adjusting for imbalances, patients with TMB ≥ 10 had more favorable PFS (HR, 0.51; 95% CI, 0.32 to 0.82), TTNT (HR, 0.56; 95% CI, 0.35 to 0.91), and OS (HR, 0.56; 95% CI, 0.29 to 1.08) on ICPI versus chemotherapy, but not TMB < 10. Comparisons unadjusted for imbalances had similar associations. CONCLUSIONS: In real-world settings, mUC patients with TMB ≥ 10 have more favorable outcomes on first-line single-agent ICPI than carboplatin, adding clinical validity to TMB assessed by an existing US Food and Drug Administration-approved platform.