Cabozantinib (C) exposure-response (ER) analysis for the phase 3 CheckMate 9ER (CM 9ER) trial of nivolumab plus cabozantinib (N+C) versus sunitinib (S) in first-line advanced renal cell carcinoma (1L aRCC).

2021 ◽  
Vol 39 (15_suppl) ◽  
pp. 4561-4561
Author(s):  
Amishi Yogesh Shah ◽  
Robert J. Motzer ◽  
Andrea B. Apolo ◽  
Thomas Powles ◽  
Bernard Escudier ◽  
...  

4561 Background: In the phase 3 CM 9ER trial (NCT03141177), N+C significantly improved progression-free survival (PFS; HR 0.51, 95% CI 0.41–0.64; p < 0.0001), overall survival (OS; HR 0.60, 98.89% CI 0.40–0.89; p = 0.0010), and objective response rate (p < 0.0001) vs S in 1L aRCC (Choueiri, 2020). N+C was generally well tolerated with low rates of treatment-related discontinuations, indicating successful adverse event (AE) management with dose modification to maintain tolerability. Here the impact of C exposure on efficacy and safety outcomes in CM 9ER was evaluated using ER analysis. Methods: Patients (pts, N = 320) with previously untreated aRCC received C 40 mg QD in combination with N 240 mg Q2W; dose reductions of C to 20 mg QD or 20 mg Q2D were allowed to manage AEs. Time-to-event Cox proportional hazard ER models were developed to characterize the relationship between predicted C exposure or apparent clearance (CL/F) and specified endpoints, including PFS, dose modification, and select AEs (palmar-plantar erythrodysesthesia [PPE; Gr ≥1], diarrhea [Gr ≥3], hypertension [Gr ≥3], fatigue/asthenia [Gr ≥3], and ALT/AST elevation [Gr ≥3]). C exposure was defined as the overall average concentration from time zero to the time of event or censoring (CAVG) and estimated by population pharmacokinetic modeling for a typical patient. ER analysis for OS was not done due to the low number of events at the database lock date (March 30, 2020). Results: In the ER analysis of PFS, predicted C exposure at 40-mg and 20-mg QD doses was not significantly associated with the rate of progression or death (HR 1.00, 95% CI 0.78–1.27, for 20-mg vs 40-mg dose). In the ER analysis of AEs, lower predicted C exposure was significantly associated with lower rates of PPE (HR 0.63, 95% CI 0.50–0.78, for 20-mg vs 40-mg dose) and diarrhea (HR 0.48, 95% CI 0.29–0.80) but was not significantly associated with the rates of hypertension, fatigue/asthenia, or ALT/AST elevation. Higher predicted C CL/F was associated with a lower rate of C dose modification; however, this association was not statistically significant (HR 0.80, 95% CI 0.57–1.12, for CL/F 3.2 vs 1.2 L/hr). Conclusions: In ER models of pts with 1L aRCC treated with the combination of N+C, C exposure was not significantly associated with PFS; however, higher C exposure was associated with higher rates of PPE and diarrhea. ER modeling predicts that a starting dose of 40 mg QD C in combination with N with appropriate dose modifications to manage C AEs will not adversely affect the efficacy of the combination in 1L aRCC. Clinical trial information: NCT03141177.

2009 ◽  
Vol 27 (15_suppl) ◽  
pp. 2522-2522
Author(s):  
D. Sonnichsen ◽  
S. Liao ◽  
A. Berkenblit ◽  
J. Boni

2522 Background: Temsirolimus (TEMSR) is an mTOR inhibitor approved for treatment of patients with advanced renal cell carcinoma, and under development for relapsed/refractory mantle cell lymphoma (MCL). In MCL, TEMSR showed a dose-related increase in median progression-free survival [4.8 vs. 3.4 mo] and objective response rate [22% vs 6%] for 175 mg x 3 wks then 75 or 25 mg weekly regimens (175/75-mg and 175/25-mg), respectively. We aim to characterize the population pharmacokinetic exposure, covariate influence, and differences afforded by these regimens. Methods: Nonlinear mixed-effects models of TEMSR and sirolimus (SIR; major active metabolite) blood concentrations were defined in healthy subjects and patients. Modeling for TEMSR employed a 4-compartment model with saturable distribution to red cells and peripheral tissue, and modeling for SIR utilized a linear 2- compartment model with factor for dose. Covariates included demographic factors, clinical labs, and disease condition. Following validation, simulations with variability were used to evaluate effects of covariates on exposure. Results: Final datasets comprised 1342 observations from 150 subjects (TEMSR) and 1648 observations from 279 subjects (SIR). In a typical patient (56-year-old male weighing 76.5 kg), disease affected TEMSR clearance (62.4 L/h in MCL, 92.1 L/h in breast cancer vs. 112 L/h for other subjects). Dose, single vs. multiple, and body weight affected SIR apparent clearance. Simulations for the 175/75-mg regimen indicate that significant covariates yield only modest differences on blood exposures. For MCL (175/75-mg regimen), TEMSR Cmax (week 3) was 2574 ng/mL and SIR Ctrough (week 6) was 10.7 ng/mL. AUC for the 75-mg maintenance arm was ∼2.3-fold (TEMSR) and ∼3.5-fold higher (SIR) than respective values of the 25-mg arm. Correlation of average AUC to clinical response was not apparent. Conclusions: No significant differential effects were observed for age, gender, race, or hepatic and renal laboratory measures. Covariates of disease, while significant, have only modest effects on the exposure profile. Higher clinical responses observed with the 175/75-mg regimen as compared with the 175/25-mg regimen may critically derive from differences in exposure. [Table: see text]


2020 ◽  
Vol 8 (Suppl 3) ◽  
pp. A328-A328
Author(s):  
Paolo Ascierto ◽  
Karl Lewis ◽  
Caroline Robert ◽  
Daniil Stroyakovskiy ◽  
Helen Gogas ◽  
...  

BackgroundThe phase 3 IMspire150 study (NCT02908672) demonstrated improved progression-free survival (PFS) with first-line atezolizumab (A) vs placebo (P) combined with vemurafenib (V) + cobimetinib (C) in patients with BRAFV600 mutation–positive advanced melanoma (15.1 vs 10.6 months; hazard ratio [HR] 0.78; 95% confidence interval [CI] 0.63–0.97; P=0.0249). Objective response has been associated with increased survival with chemotherapy and targeted therapies, but it is unclear whether the association holds for immunotherapy. In this exploratory analysis, we evaluated the impact of response on survival outcomes in patients treated with A+V+C or P+V+C in the IMspire150 study.Methods514 patients were randomized 1:1 to A+V+C (n=256) or P+V+C (n=258). Patients received V+C in cycle 1; A or P was added on days 1+15 from cycle 2 onward. The primary endpoints for this exploratory analysis were PFS and overall survival (OS), estimated using the Kaplan-Meier method. Outcomes were analyzed by investigator-assessed best overall response (BOR) per RECIST v1.1 (complete response [CR] vs partial response [PR] vs stable disease [SD]).ResultsMedian follow-up was 18.9 mo. In the A+V+C arm, BOR was CR (n=41), PR (n=129), and SD (n=58); in the P+V+C arm, BOR was CR (n=46), PR (n=122), and SD (n=58). An imbalance in baseline prognostic factors (eg, lactate dehydrogenase, tumor burden measures) was noted across response categories in both treatment arms, with favorable factors more prevalent in patients with CR and unfavorable factors more prevalent in patients with PR/SD. Improvement in PFS and OS was observed with A+V+C vs P+V+C in patients with PR, with 2-year PFS rates of 42.1% vs 24.6% and 2-year OS rates of 69.1% vs 56.1% with A+V+C vs P+V+C (table 1). In patients with CR, median PFS and OS were not yet reached in either arm, with 2-year PFS rates of 64.6% vs 59.8% and 2-year OS rates of 82.6% vs 82.8% with A+V+C vs P+V+C. PFS and OS outcomes were poor in both treatment arms in patients with SD, with 2-year PFS rates of 10.7% vs not estimable (NE) and 2-year OS rates of 36.6% vs 29.3% with A+V+C vs P+V+C.Abstract 301 Table 1PFS and OS outcomes with A+V+C vs P+V+C by BOR per RECIST v1.1ConclusionsPFS and OS improvement was observed for A+V+C vs P+V+C for patients who achieved PR. CR is associated with improved PFS and OS with both A+V+C and P+V+C. Further follow-up is required to determine the impact of A+C+V vs P+C+V on survival outcomes.Trial RegistrationClinicalTrials. gov, NCT02908672


2021 ◽  
Vol 39 (6_suppl) ◽  
pp. 359-359
Author(s):  
Emeline Colomba ◽  
Ronan Flippot ◽  
Cécile Dalban ◽  
Sylvie Negrier ◽  
Christine Chevreau ◽  
...  

359 Background: Statins are HMG-CoA inhibitors that regulate several mechanisms involved in tumor growth, including mitochondrial metabolism, activation of oncogenic signaling pathways, and immune modulation. Population-based studies showed that statin intake may be negatively associated with RCC onset. The impact of statins on response to immunotherapy in mRCC is unknown. Herein we study the association between statin administration and outcomes in patients with mRCC treated with nivolumab in the NIVOREN-GETUG AFU 26 phase II trial (NCT03013335). Methods: Patients with mRCC who failed previous VEGFR inhibitors were included. We assessed nivolumab activity, including objective response rate (ORR), progression-free survival (PFS), and overall survival (OS) according to statin intake at baseline. Toxicity was assessed using CTCAE v4.0. Results: Overall,133 patients were treated with statins at baseline among 702 evaluable for concomitant therapies (19%). Among them, median age was 68 (49-90), 84% were male, 85% had a performance status ≥ 80%, 42% were overweight and 20% obese. Patients treated with statins had mostly good (23%) or intermediate (58%) IMDC risk, 64% had grade 3 or 4 tumors, and nivolumab was given in a third line setting or more in 55%. Median follow-up was 23.9 months (95%CI 23.0-24.5) in the overall cohort. The ORR was 26% in patients treated with statins, PFS 5.0 months (CI95% 3.0 – 5.5), OS 27.9 months (CI95% 19.4-30.3). Outcomes of patients with or without statins did not differ significantly. Similar rates of grade 3-5 TRAE were reported in patients with (20%) or without (18%) statin intake. Conclusions: This is the first study to evaluate statin intake and outcomes with nivolumab in patients with mRCC. Despite numerically higher ORR, statins were not significantly associated with improved outcomes. These data require other analyzes considering other factors such as BMI and other comorbidities. Further studies may help better understand the interplay between immunity and metabolic reprogramming in RCC.


2021 ◽  
Vol 39 (15_suppl) ◽  
pp. 1077-1077
Author(s):  
Joyce O'Shaughnessy ◽  
Kevin Punie ◽  
Mafalda Oliveira ◽  
Filipa Lynce ◽  
Sara M. Tolaney ◽  
...  

1077 Background: In pts with pretreated mTNBC, standard-of-care chemotherapy is associated with low objective response rates (ORRs) and short median progression-free survival (PFS). SG is an antibody-drug conjugate composed of an anti–Trop-2 antibody coupled to the cytotoxic SN-38 payload via a proprietary, hydrolyzable linker. SG received accelerated FDA approval for treatment of pts with mTNBC who have received ≥2 prior therapies for metastatic disease. The confirmatory phase 3 ASCENT study (NCT02574455) in pts with relapsed/refractory mTNBC demonstrated a significant survival benefit of SG over TPC (median PFS: 5.6 vs 1.7 mo, HR 0.41, P< 0.0001; median overall survival [OS]: 12.1 vs 6.7 mo, HR 0.48, P< 0.0001) with a tolerable safety profile. Here we summarize efficacy results for SG vs each TPC agent in ASCENT to examine how each TPC agent performed individually. Methods: Pts had mTNBC refractory to or progressing after ≥2 prior standard chemotherapy regimens. Pts were randomized 1:1 to receive SG (10 mg/kg intravenously on days 1 and 8, every 21 days) or single-agent TPC (eribulin, vinorelbine, capecitabine, or gemcitabine). Primary endpoint was PFS per RECIST 1.1 by independent review in brain metastases-negative (BMNeg) pts. Secondary endpoints were ORR per RECIST 1.1, duration of response, OS, and safety. Outcomes for each of the agents in the TPC arm were analyzed and compared with SG. Results: Of 529 pts enrolled, 468 were BMNeg. Among pts in the TPC cohort (n = 233), eribulin was the most commonly chosen chemotherapy (n = 126), followed by vinorelbine (n = 47), capecitabine (n = 31), and gemcitabine (n = 29). Treatment with eribulin, vinorelbine, capecitabine, and gemcitabine resulted in shorter median PFS vs SG (2.1, 1.6, 1.6, and 2.7 vs 5.6 mo, respectively); similar results were observed for median OS (6.9, 5.9, 5.2, and 8.4 vs 12.1 mo), ORR (5%, 4%, 6%, and 3% vs 35%), and clinical benefit rate (CBR; 8%, 6%, 10%, and 14% vs 45%). Key grade ≥3 treatment-related adverse events (TRAEs) with TPC overall vs SG included neutropenia (33% vs 51%), leukopenia (5% vs 10%), fatigue (5% vs 3%), and anemia (5% vs 8%). Key grade ≥3 TRAEs with eribulin vs SG included neutropenia (30% vs 51%), leukopenia (5% vs 10%), fatigue (5% vs 3%), anemia (2% vs 8%), and peripheral neuropathy (2% vs none), respectively. The safety profiles of vinorelbine, capecitabine, and gemcitabine combined were consistent with that of TPC overall and with eribulin. One treatment-related death was reported for the TPC arm (eribulin) and none with SG. Conclusions: The efficacy benefit observed with SG vs TPC in pts with mTNBC was retained when evaluating each TPC chemotherapy agent individually. These results confirm that SG should be considered as a new standard of care in pts with pretreated mTNBC. Clinical trial information: NCT02574455 .


2021 ◽  
Vol 39 (15_suppl) ◽  
pp. e21587-e21587
Author(s):  
Ting Ye ◽  
Jieying Zhang ◽  
Xinyi Liu ◽  
Mengmei Yang ◽  
Yuhan Zhou ◽  
...  

e21587 Background: Immunotherapies targeting immune checkpoint receptors have become the cornerstone of systemic treatment options for malignant melanoma. The response to these immunotherapies may correlate with driver mutations. MAP2K1/2 genes are mutated in approximately 10% of melanomas, however, the impact of MAP2K1/2 gene alterations on the efficiency of immunotherapy has not been clarified. Methods: Six metastatic melanoma clinical cohorts treated with ICIs were included to investigate the association between clinical efficacy of immunotherapy and MAP2K1/2 mutations. Survival analyses were conducted in cohorts receiving two kinds of ICB agents, namely anti-CTLA-4 or anti-PD-1. RNA expression profiling from these cohorts and from the TCGA melanoma cohort were used to explore the potential mechanism related to immune activation. Results: In an independent anti-CTLA-4-treated cohort (n = 110), we found that MAP2K1/2 mutations are predictive of high objective response rate (17.6% vs 1.3%, p = 0.0185) and long progression-free survival [median OS, 49.2 months vs 8.3 months; hazard ratio (HR) = 0.37; 95% CI, 0.15–0.91; p = 0.0307] and overall survival (median PFS, 19.4 months vs 2.8 months; HR = 0.2; 95% CI, 0.05–0.83; p = 0.0262). This predictive value was further validated in a pooled anti-CTLA-4-treated cohort (n = 235) in terms of overall survival (median OS, 49.3 months vs 22.0 months; HR = 0.44; 95% CI, 0.22–0.91; p = 0.0255). However, no correlation between MAP2K1/2 mutations and overall survival was observed in the anti-PD-1-treated cohort (n = 285). Subgroup Cox regression analysis indicated that MAP2K-mutated patients receive less benefit from the anti-PD-1 monotherapy than from the anti-CTLA-4 treatment (median OS, 27.0 months vs 49.3 months; HR = 3.26; 95% CI, 1.18–9.02; p = 0.0225), which was contrary to the result obtained for the total population. Furthermore, transcriptome profiling analysis revealed that MAP2K-mutated tumors are enriched in CD8+ T cells, B cells, and neutrophil cells and also express high levels of CD33 and IL10, which might be the underlying mechanism for melanoma patients with MAP2K1/2-mutated benefit more from anti-CTLA-4 treatment. Conclusions: We identified mutations in MAP2K1/2 genes as the independent predictive factors for anti-CTLA-4 therapy in melanoma patients and found that anti-CTLA-4 treatment in patient harbouring MAP2K1/2 mutations might be more effective than the anti-PD-1 therapy.


Cells ◽  
2020 ◽  
Vol 9 (9) ◽  
pp. 2071
Author(s):  
Jihane Boustani ◽  
Valentin Derangère ◽  
Aurélie Bertaut ◽  
Olivier Adotevi ◽  
Véronique Morgand ◽  
...  

In locally advanced rectal cancer, radiotherapy (RT) followed by surgery have improved locoregional control, but distant recurrences remain frequent. Although checkpoint inhibitors have demonstrated objective response in several cancers, the clinical benefit of PD-1/PD-L1 blockade remains uncertain in rectal cancer. We collected data from biopsies and surgical specimens in 74 patients. The main objective was to evaluate the impact of neoadjuvant RT and fractionation on PD-L1 expression. Secondary objectives were to study the relation between PD-L1 expression and tumor regression grade (TRG), progression-free survival (PFS), overall survival (OS), and CD8 TILs infiltration. Median rates of cells expressing PD-L1 pre- and post-RT were 0.15 (range, 0–17) and 0.5 (range, 0–27.5), respectively (p = 0.0005). There was no effect of RT fractionation on PD-L1+ cell rates. We found no relation between CD8+ TILs infiltration and PD-L1 expression and no difference between high-PD-L1 or low-PD-L1 expression and TRG. High-to-high PD-L1 expression profile had none significant higher OS and PFS compared to all other groups (p = 0.06). Median OS and PFS were higher in biopsies with >0.08 PD-L1+ cells. High-to-high PD-L1 profile and ypT0-2 were significantly associated with higher OS and PFS. This study did not show the differential induction of PD-L1 expression according to fractionation.


2013 ◽  
Vol 31 (15_suppl) ◽  
pp. 3636-3636 ◽  
Author(s):  
Eric van Cutsem ◽  
Alberto Sobrero ◽  
Salvatore Siena ◽  
Alfredo Falcone ◽  
Marc Ychou ◽  
...  

3636 Background: In the CORRECT phase III trial, the multikinase inhibitor REG demonstrated significant improvement in overall survival (OS) and progression-free survival vs placebo (Pla) in patients (pts) with mCRC whose disease progressed on other standard therapies. The most frequent REG-related grade ≥3 adverse events (AEs) of interest were hand–foot skin reaction (HFSR), fatigue, diarrhea, hypertension, and rash/desquamation. We explored whether the impact of REG in pts aged ≥65 years differed from that in younger patients. Methods: Pts with mCRC progressing following all other available therapies were randomized 2:1 to receive REG 160 mg once daily (n=505) or Pla (n=255) for the first 3 weeks of each 4-week cycle. The dose could be modified to manage AEs. The primary endpoint was OS. We report efficacy, safety, and dosing data from REG recipients by age. Results: The REG treatment group included 309 pts <65 years (307 evaluable for safety) and 196 pts ≥65 years (193 evaluable for safety). The OS hazard ratio (REG/Pla) was 0.72 (95% confidence interval [CI] 0.56–0.91) in pts <65 years and 0.86 (95% CI 0.61–1.19) in pts ≥65 years (interaction p-value = 0.405). Median OS was 6.7 vs 5 months for REG vs Pla in pts <65 years, and 6.0 vs 5.6 months, respectively, in pts ≥65 years. Most pts experienced drug-related AEs (<65 years: 93.8%; ≥65 years: 91.7%). The rates of grade ≥3 REG-related AEs of interest and dose modifications are shown in the Table. In pts <65 years vs ≥65 years, median (interquartile range [IQR]) duration of REG was 7.6 weeks (6.6–15.4) vs 7.1 weeks (5.1–17.2), median (IQR) daily REG dose was 160.0 mg (134.6–160.0) vs 160.0 mg (137.5–160.0), and median (IQR) proportion of planned REG dose was 83.3% (65.7–100.0) vs 78.6% (66.7–100.0), respectively. Conclusions: In the CORRECT trial, REG demonstrated an OS benefit in pts <65 years and ≥65 years. Safety and tolerability of REG appeared to be similar in both age subgroups. Clinical trial information: NCT01103323. [Table: see text]


2015 ◽  
Vol 33 (3_suppl) ◽  
pp. 705-705
Author(s):  
Timothy Jay Price ◽  
Marc Peeters ◽  
Tae Won Kim ◽  
Jin Li ◽  
Stefano Cascinu ◽  
...  

705 Background: ASPECCT met its primary endpoint of non-inferiority of overall survival (OS) of pmab vs. cmab. We evaluate outcomes by hypomag, an on-treatment, anti-EGFR related adverse event that develops due to the inhibition of EGFR function. Conflicting reports have suggested hypomag is associated with survival. Methods: Patients with previously treated WT KRAS exon 2 mCRC were randomized 1:1 to receive pmab or cmab. The primary endpoint was non-inferiority of OS. Progression-free survival (PFS) and objective response rate (ORR) were secondary endpoints. Patients were categorized ± any grade hypomag during the study and data analyzed by treatment arm. Analysis of Mg supplementation during hypomag was not conducted. Results: 999 patients were randomized and treated: 499 pmab, 500 cmab. Any grade hypomag was 28.8% and grade ≥3 was 7.3% in the pmab arm vs. 18.9% and 2.6% in the cmab arm, respectively. Median time to first hypomag onset was 82 days in the pmab arm and 57 days in the cmab arm. In the pmab arm, 1.0% of patients discontinued treatment and 5% of patients had dose modifications due to hypomag vs. <0.5% and 3% in the cmab arm, respectively. Results are shown (Table). Conclusions: In ASPECCT, rates of hypomag were higher in the pmab vs. the cmab arm. Patients who developed any grade hypomag with pmab or cmab had higher ORR, PFS, and OS compared with those patients who did not. Clinical trial information: NCT00788957. [Table: see text]


2015 ◽  
Vol 33 (7_suppl) ◽  
pp. 200-200 ◽  
Author(s):  
Julie Nicole Graff ◽  
Giulia Baciarello ◽  
Andrew J. Armstrong ◽  
Celestia S. Higano ◽  
Peter Iversen ◽  
...  

200 Background: In the phase 3 PREVAIL trial, enzalutamide (ENZA), an androgen receptor inhibitor, improved overall survival (OS) and radiographic progression-free survival (rPFS) relative to placebo (PBO) in chemotherapy-naïve men with mCRPC. Methods: PREVAIL randomized 1,717 patients (pts) with asymptomatic or minimally symptomatic chemotherapy-naïve mCRPC 1:1 to ENZA 160 mg daily or PBO. Coprimary endpoints were OS and rPFS. This prespecified analysis evaluated the impact of age (≥ 75 vs < 75 years) on efficacy and safety. Results: In PREVAIL, 609 (35%) pts were aged ≥ 75 years. This older subset had several poorer baseline prognostics relative to those aged < 75 years: worse ECOG performance status (ECOG 1: 45.0% vs 24.7%), higher prostate-specific antigen (PSA; 73.3 vs 37.3 ng/mL) and more cardiovascular disease (26.9% vs 16.5%). In both older and younger pts, ENZA improved OS, rPFS and time to PSA progression (Table). Pts aged ≥ 75 years in both the ENZA and PBO groups combined had a higher rate of grade ≥ 3 adverse events (46% vs 37% in younger pts) and among enzalutamide-treated men more older pts reported falls (any grade; ENZA 19% and PBO 8%) than younger pts (ENZA 7% and PBO 4%). Fewer pts ≥ 75 years received subsequent antineoplastic therapies. Conclusions: In PREVAIL, efficacy outcomes in elderly (≥ 75 years) and younger (< 75 years) pts with chemotherapy-naïve mCRPC were comparable and pts consistently benefited from ENZA treatment. Safety with ENZA was similar in both age groups, although older pts reported a higher incidence of falls and received fewer subsequent antineoplastic therapies. Clinical trial information: NCT01212991. [Table: see text]


2019 ◽  
Vol 37 (8_suppl) ◽  
pp. 43-43 ◽  
Author(s):  
Marwan Fakih ◽  
Jaideep Singh Sandhu ◽  
Ching Ouyang ◽  
Ethan Sokol ◽  
Jeffrey S. Ross ◽  
...  

43 Background: PD-1 targeting with pembrolizumab or nivolumab leads to durable clinical benefits in patients (pts) with microsatellite instability-high (MSI-H) tumors. However, 30-35% of mCRC pts with MSI-H tumors will experience progressive disease (PD) as a best response when treated with anti-PD1 agents, highlighting the need of additional predictive biomarkers. Methods: We performed a retrospective multi-center clinical investigation to evaluate the impact of TMB, age, gender, stage at initial presentation, pattern of metastatic disease, tumor grade, and RAS/RAF status on response to anti-PD1/PD-L1 in MSI-H mCRC. TMB and MSI status were determined by hybrid capture-based next-generation sequencing (Foundation Medicine [FM]). The TMB distribution in MSI-H CRC was estimated from a large data set from FM. Results: 22 eligible MSI-H mCRC pts were identified across 5 cancer centers: 19 pts received pembrolizumab, 1 pt received nivolumab, 1 pt received nivolumab + ipilimumab, and 1 pt received durvalumab + tremelimumab. Among tested variables, TMB (as a continuous variable) showed the strongest association with an objective response (OR; p < 0.001). Also, both univariate and multivariate analyses supported that TMB serves as an independent prognostic variable in predicting progression-free survival (PFS; p < 0.001 and p < 0.01, respectively). Using log-rank statistics, the optimal predictive cut-point for TMB was estimated between 37-41 mutations/Mb to dichotomize pts into TMBhigh and TMBlow groups. All 13 pts (100%) with TMBhigh had an OR, while only 2/9 (22%) pts with TMBlow had an OR and 6/9 had PD. The median PFS for TMBhigh pts has not been reached (no progressors, median follow-up > 18 mos), while the median PFS for TMBlow pts was 2 mos. Amongst 821 MSI-H CRC cases tested at FM, the 25th, 35th, 50th and 75th percentile TMB cutoffs were 33.1, 37.4, 46.1, and 61.8 mutations/Mb, respectively. Our optimal TMB cut-point range suggests that MSI-H mCRC with the lowest 35th percentile of TMB have a low likelihood of benefit from anti-PD1. Conclusions: These TMB findings require validation in prospective trials and may guide the sequencing of PD-1 inhibitor monotherapy in MSI-H mCRC.


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