1O Nivolumab (NIVO) plus ipilimumab (IPI) vs NIVO monotherapy for microsatellite instability-high/mismatch repair-deficient (MSI-H/dMMR) metastatic colorectal cancer (mCRC): Health-related quality of life (HRQoL) analyses from CheckMate 8HW

3501 Background: In the phase 3 CheckMate 8HW study (NCT04008030), both dual primary endpoints of progression-free survival (PFS) for first-line (1L) NIVO + IPI vs chemo (HR 0.21; P < 0.0001) and NIVO + IPI vs NIVO across all lines (HR 0.62; P = 0.0003) in patients (pts) with centrally confirmed MSI-H/dMMR mCRC were met. We report expanded analyses of NIVO + IPI vs NIVO (all lines) and longer follow-up results for NIVO + IPI vs chemo (1L). Methods: The study design was described previously. Pts with MSI-H/dMMR per local testing were enrolled. After randomization, IHC and PCR based tests were used for central confirmation. PFS2 (time from randomization to progression after subsequent systemic therapy, start of second subsequent systemic therapy, or death) was a key exploratory endpoint. Results: In all randomized pts (all lines), 296 of 354 (84%) in the NIVO + IPI arm, 286 of 353 (81%) in the NIVO arm, and 113 of 132 (86%) in the chemo arm had centrally confirmed MSI-H/dMMR. In all randomized 1L pts, 171 of 202 (85%) in the NIVO + IPI arm and 84 of 101 (83%) in the chemo arm had centrally confirmed MSI-H/dMMR. Median follow-up was 47.0 mo (range 16.7–60.5). 1L NIVO + IPI continued to show PFS benefit vs chemo (Table). Subsequent systemic therapy was received by 27 (16%) and 61 (73%) pts after 1L NIVO + IPI and chemo, respectively; 10 (6%) and 21 (25%) received subsequent non-study immunotherapy. In the 1L chemo arm, 39 (46%) pts crossed over to NIVO + IPI on study. PFS2 continued to favor 1L NIVO + IPI vs chemo (Table). Across all lines, NIVO + IPI demonstrated superior PFS vs NIVO (Table). Subsequent systemic therapy was received by 54 (18%) pts in the NIVO + IPI arm and 83 (29%) in the NIVO arm; 20 (7%) and 31 (11%) received subsequent non-study immunotherapy. PFS2 favored NIVO + IPI vs NIVO across all lines of therapy (Table). In all treated pts, grade 3/4 treatment-related adverse events occurred in 78 (22%) and 50 (14%) pts in the NIVO + IPI and NIVO arms, respectively. Additional analyses will be presented. Conclusions: NIVO + IPI demonstrated sustained clinical benefit vs chemo (1L) and NIVO (all lines) despite use of subsequent therapy, as shown by improved PFS2 in pts with centrally confirmed MSI-H/dMMR mCRC. No new safety signals were observed. These results support NIVO + IPI as a standard of care treatment for MSI-H/dMMR mCRC. Clinical trial information: NCT04008030 . Centrally confirmed MSI-H/dMMR (1L) NIVO + IPI(n = 171) Chemo(n = 84) Median PFS (95% CI), mo 54.1 (54.1–NE) 5.9 (4.4–7.8) HR (95% CI) 0.21 (0.14–0.31) Median PFS2 (95% CI), mo NR (NE–NE) 30.3 (15.2–NE) HR (95% CI) 0.28 (0.18–0.44) Centrally confirmed MSI-H/dMMR (all lines) NIVO + IPI (n = 296) NIVO (n = 286) Median PFS (95% CI), mo NR (53.8–NE) 39.3 (22.1–NE) HR (95% CI) 0.62 (0.48-0.81); P = 0.0003 Median PFS2 (95% CI), mo NR (NE–NE) NR (NE–NE) HR (95% CI) 0.57 (0.42–0.78) NE, not evaluable; NR, not reached.

LBA143 Background: The CheckMate 8HW study met its dual primary endpoint with NIVO + IPI demonstrating superior progression-free survival (PFS) by blinded independent central review (BICR) vs chemotherapy (chemo) in patients (pts) with centrally confirmed MSI-H/dMMR mCRC in the first-line (1L) setting (HR 0.21; 95% CI 0.14–0.32; P < 0.0001). We report first results from the other dual primary endpoint of PFS for NIVO + IPI vs NIVO across all lines of therapy in pts with centrally confirmed MSI-H/dMMR mCRC. Methods: Immunotherapy-naive pts with unresectable or mCRC and MSI-H/dMMR status by local testing who had received 0 or 1 prior line of therapy were randomized 2:2:1 to (i) NIVO (240 mg) Q2W (6 doses, then NIVO 480 mg Q4W), (ii) NIVO (240 mg) + IPI (1 mg/kg) Q3W (4 doses, then NIVO 480 mg Q4W), or (iii) chemo ± targeted therapies. Pts who had received ≥ 2 prior lines of therapy were randomized 1:1 to the NIVO + IPI or NIVO arms. Treatments continued until disease progression or unacceptable toxicity (all arms), or a maximum of 2 years (NIVO ± IPI arms). Results: Across all lines of therapy,707 pts were randomized to NIVO + IPI (n = 354) or NIVO (n = 353); 55% and 52% received study treatment in the 1L setting, respectively. Of all randomized pts, 296 in the NIVO + IPI arm and 286 in the NIVO arm had centrally confirmed MSI-H/dMMR status. With 47.0 months (mo) of median follow-up (range, 16.7–60.5), NIVO + IPI demonstrated clinically meaningful and statistically significant improvement in PFS by BICR vs NIVO (HR 0.62; 95% CI 0.48–0.81; P = 0.0003) and higher 12-, 24-, and 36-mo PFS rates vs NIVO (Table). Objective response rate (ORR) by BICR was significantly higher with NIVO + IPI vs NIVO (71% vs 58%; P = 0.0011; Table); best overall response of progressive disease was reported in 10% and 19% of pts, respectively. No new safety concerns were identified (Table). Conclusions: In the first randomized study to compare dual- vs single-agent immunotherapy in MSI-H/dMMR mCRC, NIVO + IPI demonstrated superior PFS vs NIVO across all lines of therapy, with a manageable safety profile. These results establish NIVO + IPI as the potential new standard-of-care treatment for MSI-H/dMMR mCRC. Clinical trial information: NCT04008030 . Efficacy by BICR (all lines; centrally confirmed MSI-H/dMMR by IHC and/or PCR test) NIVO + IPI(n = 296) NIVO(n = 286) Median PFS (95% CI), mo NR (53.8–NE) 39.3 (22.1–NE) HR (95% CI); P value 0.62 (0.48–0.81); 0.0003 PFS rate (12/24/36-mo), % 76/71/68 63/56/51 ORR, n (%); 95% CI, % 209 (71); 65–76 165 (58); 52–64 P value 0.0011 Safety (all lines; all treated), n (%) NIVO + IPI (n = 352) NIVO (n = 351) Any-grade/grade 3–4 TRAEs 285 (81)/78 (22) 249 (71)/50 (14) Any-grade/grade 3–4 TRAEs leading to discontinuation 48 (14)/33 (9) 21 (6)/14 (4) Treatment-related deaths 2 (< 1) 1 (< 1) IHC, immunohistochemistry; NE, not estimable; NR, not reached; PCR, polymerase chain reaction; TRAE, treatment-related adverse event.

Early detection and management of treatment-related adverse events (TRAEs) in patients receiving immune checkpoint inhibitors may improve outcomes. In CheckMate 142, nivolumab (3 mg/kg) plus low-dose ipilimumab (1 mg/kg) provided durable clinical benefit (objective response rate [ORR] 55%, median duration of response not reached, 12-month overall survival [OS] rate 85%) and manageable safety for previously treated microsatellite instability-high and/or mismatch repair-deficient (MSI-H/dMMR) metastatic colorectal cancer (mCRC). In-depth safety and additional efficacy outcomes from CheckMate 142 are presented. Safety assessments included frequency of TRAEs, select TRAEs (sTRAEs), and immune-mediated adverse event incidences; time to onset (TTO); time to resolution (TTR); immune-modulating medication (IMM) use; dose delay; and sTRAE occurrence after resuming therapy. Efficacy assessments included ORR and survival analyses in patients with sTRAEs with or without concomitant IMM treatment and patients without sTRAEs. Among 119 patients, 25%, 23%, 19%, 5%, 5%, and 29% experienced an endocrine, gastrointestinal, hepatic, pulmonary, renal, or skin sTRAE, respectively; the majority (57%) were grade 1/2. sTRAEs occurred early (median TTO, 5.2-12.6 weeks). Nonendocrine sTRAEs resolved in most (>71%) patients (median TTR, 1.5-9.0 weeks). IMMs were used to manage sTRAEs in 22%-56% of patients (most resolved). Of patients with dose delay because of sTRAEs, 25 of 29 resumed treatment. Patients with or without sTRAEs had comparable ORR (57% vs. 52%) and 12-month OS rates (93% vs. 75%). Similar results were observed in patients with or without sTRAEs regardless of IMM use (ORR 52% vs. 57%; OS rates 87% vs. 82%). The benefit-risk profile of nivolumab plus low-dose ipilimumab provides a promising treatment option for patients with previously treated MSI-H/dMMR mCRC. Nivolumab (NIVO) plus low-dose (1 mg/kg) ipilimumab (IPI) received U.S. Food and Drug Administration approval for patients with microsatellite instability-high and/or mismatch repair-deficient (MSI-H/dMMR) metastatic colorectal cancer (mCRC) that progressed following treatment with a fluoropyrimidine, oxaliplatin, and irinotecan based on results from CheckMate 142. In this safety analysis, the majority of select treatment-related adverse events (sTRAEs) occurred early, were managed using evidence-based treatment algorithms, and resolved. Efficacy outcomes were comparable between patients with or without sTRAEs regardless of the use of concomitant immune-modulating medications. The benefit-risk profile of NIVO + low-dose IPI provides a promising treatment option for MSI-H/dMMR mCRC.

3503 Background: NIVO + IPI demonstrated superior progression-free survival (PFS) vs chemo in patients (pts) with previously untreated MSI-H/dMMR mCRC in the randomized phase 3 CheckMate 8HW study (NCT04008030). We report expanded efficacy analysis from the prespecified interim analysis of NIVO + IPI vs chemo in the 1L setting. Methods: Pts with unresectable or mCRC and MSI-H/dMMR status by local testing were enrolled across different lines of therapy and randomized 2:2:1 to NIVO (240 mg) + IPI (1 mg/kg) Q3W (4 doses, then NIVO 480 mg Q4W), NIVO (240 mg) Q2W (6 doses, then NIVO 480 mg Q4W), or chemo ± targeted therapies; treatments continued until disease progression or unacceptable toxicity (all arms) or for up to 2 years (NIVO ± IPI arms). In pts with blinded independent central review (BICR)–documented progression with chemo, crossover to NIVO + IPI was permitted. Dual primary endpoints were PFS by BICR per RECIST v1.1 for NIVO + IPI vs chemo (1L) and NIVO + IPI vs NIVO (all lines) in pts with centrally confirmed MSI-H/dMMR mCRC. PFS2 (time from randomization to progression after subsequent systemic therapy, initiation of second subsequent systemic therapy, or death) was a key exploratory endpoint. Results: Among 303 pts randomized to NIVO + IPI (n = 202) or chemo (n = 101), 171 pts in the NIVO + IPI arm and 84 pts in the chemo arm had centrally confirmed MSI-H/dMMR. At 31.5-months (mo) median follow-up (range 6.1–48.4), NIVO + IPI demonstrated superior PFS vs chemo (HR 0.21; 97.91% CI 0.13–0.35; P < 0.0001). Subsequent systemic therapy was received by 20 (12%) and 57 (68%) pts in the NIVO + IPI and chemo arms, respectively. In the chemo arm, 56 (67%) pts received subsequent immunotherapy (39 [46%] crossed over to NIVO + IPI on study; 17 [20%] received non-study immunotherapy). Median PFS2 was not reached (NR) with NIVO + IPI and 29.9 mo with chemo (HR 0.27; 95% CI 0.17–0.44; Table). Any grade and grade 3/4 treatment-related adverse events (TRAEs) are presented (Table). Treatment-related deaths were reported for 2 pts in the NIVO + IPI arm. Conclusions: Clinical benefit with 1L NIVO + IPI vs chemo was maintained after subsequent therapy, as shown by improved PFS2 in pts with centrally confirmed MSI-H/dMMR mCRC. No new safety concerns were identified with NIVO + IPI. These results further support NIVO + IPI as a standard-of-care 1L treatment option for pts with MSI-H/dMMR mCRC. Clinical trial information: NCT04008030 . [Table: see text]

LBA768 Background: Patients (pts) with MSI-H/dMMR mCRC have poor outcomes with standard chemo ± targeted therapies. NIVO ± IPI are approved in previously treated pts with MSI-H/dMMR mCRC in many countries, based on the phase 2 CheckMate 142 study. CheckMate 8HW (NCT04008030) is a randomized phase 3 study comparing NIVO + IPI with NIVO or chemo in pts with MSI-H/dMMR mCRC. We report progression-free survival (PFS) by blinded independent central review (BICR) at a prespecified interim analysis for NIVO + IPI vs chemo in the 1L setting. Methods: Pts ≥ 18 years with recurrent or mCRC not amenable to surgery and MSI-H/dMMR status per local testing were enrolled across different lines of therapy. Previously untreated pts were randomized 2:2:1 to NIVO (240 mg) + IPI (1 mg/kg) Q3W (4 doses, then NIVO 480 mg Q4W), NIVO (240 mg) Q2W (6 doses, then NIVO 480 mg Q4W), or chemo ± targeted therapies; treatments continued until disease progression or unacceptable toxicity (all arms), or a maximum of 2 years (NIVO ± IPI arms). For pts with BICR-documented progression with chemo, optional crossover to NIVO + IPI was permitted. Dual primary endpoints were PFS by BICR per RECIST v1.1 for NIVO + IPI vs chemo (1L) and NIVO + IPI vs NIVO (all lines) in pts with centrally confirmed MSI-H/dMMR mCRC. Results: In the 1L setting, 303 pts were randomized to NIVO + IPI (n = 202) or chemo (n = 101); of these pts, 171 pts in the NIVO + IPI arm and 84 pts in the chemo arm had centrally confirmed MSI-H/dMMR result by either immunohistochemistry and/or polymerase chain reaction-based tests. With 24.3 months of median follow-up, NIVO + IPI demonstrated clinically meaningful and statistically significant improvement in PFS vs chemo, with a 79% reduction in the risk of disease progression or death (HR 0.21 [95% CI 0.14–0.32]; P < 0.0001) (Table). No new safety signals were identified (Table). Conclusions: NIVO + IPI demonstrated superior PFS vs chemo in previously untreated pts with MSI-H/dMMR mCRC. NIVO + IPI had a different safety profile compared to chemo, with fewer grade 3–4 treatment-related adverse events (TRAEs). These results support 1L NIVO + IPI as a standard-of-care option for pts with MSI-H/dMMR mCRC. Clinical trial information: NCT04008030 . [Table: see text]

Health-related quality of life in patients with microsatellite instability-high or mismatch repair deficient metastatic colorectal cancer treated with first-line pembrolizumab versus chemotherapy (KEYNOTE-177): an open-label, randomised, phase 3 trial

Nivolumab plus low-dose ipilimumab in previously treated patients with microsatellite instability-high/mismatch repair-deficient metastatic colorectal cancer: 4-year follow-up from CheckMate 142

3510 Background: NIVO ± IPI is approved in previously treated pts with MSI-H/dMMR mCRC in the US, EU, and Japan, based on findings from the phase 2 CheckMate 142 study (NCT02060188). NCCN guidelines include NIVO + IPI as an initial therapy option for pts with MSI-H/dMMR mCRC. Results from a ~5-year follow-up from CheckMate 142 cohorts 1–3 (C1–3) are reported here. Methods: In this non-randomized, multicohort study, pts with MSI-H/dMMR mCRC were treated as follows: C1 (2L+; NIVO 3 mg/kg Q2W), C2 (2L+; NIVO 3 mg/kg + IPI 1 mg/kg Q3W [4 doses], followed by NIVO 3 mg/kg Q2W) and C3 (1L; NIVO 3 mg/kg Q2W + IPI 1 mg/kg Q6W), until disease progression or unacceptable toxicity. The primary endpoint was objective response rate (ORR) by investigator assessment (INV) per RECIST v1.1. Other key endpoints were disease control rate (DCR), duration of response (DOR), progression-free survival (PFS), all by INV and blinded independent central review; overall survival (OS), and safety. Results: In C1 (N = 74), C2 (N = 119), and C3 (N = 45), median (range) follow-up (time from first dose to data cutoff) was 70.0 (66.2–88.7), 64.0 (60.0–75.8), and 52.4 (47.6–57.1) months (mo), respectively. ORR (95% CI) by INV was 39% (28–51), 65% (55–73), and 71% (56–84; Table) and progressive disease (PD) rates were 26%, 12%, and 16% in C1, C2, and C3, respectively. Median DOR was not reached in the 3 cohorts. The 48-mo PFS rates were 36%, 54%, and 51% and 48-mo OS rates were 49%, 71%, and 72% in C1, C2, and C3, respectively (Table). PFS and OS rates with up to 60 mo of follow-up will be presented. Safety data are shown in the table. Conclusions: With extended follow-up of ~5 years, NIVO ± IPI continued to demonstrate durable OS and PFS benefit, with no new safety signals. These updated data further support current treatment recommendations for 2L+ NIVO ± IPI and 1L NIVO + IPI for pts with MSI-H/dMMR mCRC. Clinical trial information: NCT02060188. [Table: see text]

2O Health-related quality of life (HRQoL) with first-line (1L) nivolumab (NIVO) plus ipilimumab (IPI) vs chemotherapy (chemo) in patients (pts) with microsatellite instability-high (MSI-H)/mismatch repair-deficient (dMMR) metastatic colorectal cancer (mCRC): CheckMate 8HW

P-12 A phase 3 study of nivolumab (NIVO), NIVO + ipilimumab (IPI), or chemotherapy for microsatellite instability-high (MSI-H)/mismatch repair-deficient (dMMR) metastatic colorectal cancer (mCRC): CheckMate 8HW

TPS266 Background: Patients (pts) with MSI-H/dMMR mCRC treated with CT have poorer outcomes than pts with microsatellite stable/MMR proficient mCRC. NIVO (anti–programmed death [PD]-1) and IPI (anti–cytotoxic T lymphocyte antigen-4 [CTLA-4]) are immune checkpoint inhibitors that act synergistically and promote antitumor immune response by complementary mechanisms. NIVO±IPI received accelerated US FDA approval for MSI-H/dMMR mCRC that progressed after fluoropyrimidine, oxaliplatin, and irinotecan treatment based on the phase 2, non-randomized, multicohort CheckMate 142 study. Indirect comparisons suggest that NIVO (3 mg/kg) + low-dose IPI (1 mg/kg) provides improved clinical benefit vs NIVO (investigator-assessed [INV] objective response rate [ORR] 55% vs 31%; 12-month [mo] INV progression-free survival [PFS] rate 71% vs 50%; 12-mo overall survival [OS] rate 85% vs 73%) with a favorable benefit-risk profile for previously treated MSI-H/dMMR mCRC (Overman et al. JCO 2018). NIVO+low-dose IPI also demonstrated robust and durable clinical benefit in first-line MSI-H/dMMR mCRC (INV ORR 64%; 12-mo INV PFS rate 77%; 12-mo OS rate 84%; Lenz et al. ASCO 2019, #3521). To date, no prospective phase 3 studies have reported results for anti–PD-1, anti–PD-1 + anti–CTLA-4, or CT in MSI-H/dMMR mCRC; these treatments will be evaluated in the international, multicenter, open-label, randomized, phase 3 CheckMate 8HW (NCT04008030) study. Methods: Approximately 494 pts aged ≥18 years with histologically confirmed recurrent or mCRC, irrespective of prior treatment with CT and/or targeted agents, not amenable to surgery, and with known tumor MSI-H or dMMR status, and Eastern Cooperative Oncology Group performance status ≤1 will be randomized to receive NIVO, NIVO+IPI, or investigator’s choice CT (pts in the CT arm can receive NIVO+IPI upon progression). The primary endpoint is PFS, assessed by blinded independent central review (BICR). Secondary endpoints include PFS by INV, ORR and disease control rate by BICR and INV, OS, time to and duration of response. Exploratory endpoints include safety. Clinical trial information: NCT04008030.

Crossing survival curves of KEYNOTE-177 illustrate the rationale behind combining immune checkpoint inhibition with chemotherapy.

3550 Background: NIVO + IPI demonstrated robust, durable clinical benefit, and was well tolerated as a 1L therapy in pts with MSI-H/dMMR mCRC in the phase 2 CheckMate 142 study (NCT02060188), leading to the inclusion of NIVO + IPI in the NCCN guidelines as an initial therapy option for these pts. At 52-mo median follow-up, 1L NIVO + IPI continued to demonstrate durable clinical benefit, and no new safety signals were identified. Here we report longer follow-up results. Methods: Pts with MSI-H/dMMR mCRC and no prior treatment for metastatic disease received NIVO 3 mg/kg Q2W + IPI 1 mg/kg Q6W until disease progression or unacceptable toxicity. The primary endpoint was objective response rate (ORR) by investigator assessment (INV) per RECIST v1.1. Other key endpoints were disease control rate (DCR), duration of response (DOR), progression-free survival (PFS), all by INV; overall survival (OS); and safety. Results: In total, 45 pts received 1L NIVO + IPI. With median follow-up of 64.2 mo (range, 59.4–68.9 mo), ORR by INV was 71% (95% CI, 56–84%). The proportion of pts with a best overall response of complete response (CR) was 20%, partial response (PR) was 51%, stable disease (SD) was 13%, and progressive disease was 16%. Median DOR (mDOR) was not reached, and the 60-mo DOR rate was 72%. Median PFS (mPFS) by INV and median OS (mOS) were not reached, with 60-mo PFS and OS rates of 55% and 67%, respectively (Table). Among pts alive at the data cutoff (n = 31), 30 remained treatment-free after initial study treatment without receiving any subsequent systemic therapy, with a median treatment-free interval of 34.7 mo (range, 1.6–61.4 mo). Exploratory analysis by tumor mutational burden status will be presented. Safety data are shown in the Table. Conclusions: At 64-mo follow-up, NIVO + IPI continued to demonstrate clinically meaningful survival and durable responses, with mPFS, mOS, and mDOR still not reached, suggesting the potential for long-term clinical benefit. Safety remained consistent with previous data. These findings further support current recommendations for NIVO + IPI as a 1L treatment for pts with MSI-H/dMMR mCRC. Clinical trial information: NCT02060188 . [Table: see text]

97 Background: NIVO + IPI demonstrated robust, durable clinical benefit and was well tolerated as a 1L therapy in pts with MSI-H/dMMR mCRC in the phase 2 CheckMate 142 study (NCT02060188), leading to the inclusion of NIVO + IPI in the NCCN guidelines as an initial therapy option for these pts. At 52-mo median follow-up, 1L NIVO + IPI continued to demonstrate durable clinical benefit, and no new safety signals were identified. Here we report longer follow-up results. Methods: Pts with MSI-H/dMMR mCRC and no prior treatment for metastatic disease received NIVO 3 mg/kg Q2W + IPI 1 mg/kg Q6W until disease progression or unacceptable toxicity. The primary endpoint was objective response rate (ORR) by investigator assessment (INV) per RECIST v1.1. Other key endpoints were disease control rate (DCR), duration of response (DOR), progression-free survival (PFS), all by INV; overall survival (OS); and safety. Results: In total, 45 pts received 1L NIVO + IPI. With median follow-up of 64.2 mo (range, 59.4–68.9 mo), ORR by INV was 71% (95% CI, 56–84%). The proportion of pts with a best overall response of complete response (CR) was 20%, partial response (PR) was 51%, stable disease (SD) was 13%, and progressive disease was 16%. Median DOR (mDOR) was not reached, and the 60-mo DOR rate was 72%. Median PFS (mPFS) by INV and median OS (mOS) were not reached, with 60-mo PFS and OS rates of 55% and 67%, respectively (Table). Among pts alive at the data cutoff (n = 31), 30 remained treatment-free after initial study treatment without receiving any subsequent systemic therapy, with a median treatment-free interval of 34.7 mo (range, 1.6–61.4 mo). Exploratory analysis by tumor mutational burden status will be presented. Safety data are shown in the Table. Conclusions: At 64-mo follow-up, NIVO + IPI continued to demonstrate clinically meaningful survival and durable responses, with mPFS, mOS, and mDOR still not reached, suggesting the potential for long-term clinical benefit. Safety remained consistent with previous data. These findings further support current recommendations for NIVO + IPI as a 1L treatment for pts with MSI-H/dMMR mCRC. Clinical trial information: NCT02060188 . [Table: see text]

Patients with microsatellite instability-high (MSI-H)/mismatch repair-deficient (dMMR) metastatic colorectal cancer (mCRC) show a significant response to checkpoint inhibitor therapies, but the economic impact of these therapies is unknown. A decision analytic model was used to explore the effectiveness and cost burden of MSI-H/dMMR mCRC treatment. The treatment of hypothetical patients with MSI-H/dMMR mCRC was simulated in 2 treatment scenarios: a third-line treatment and an exploratory first-line treatment. The treatments compared were nivolumab, ipilimumab and nivolumab, trifluridine and tipiracil (third-line treatment), and mFOLFOX6 and cetuximab (first-line treatment). Disease progression, drug toxicity, and survival rates were based on the CheckMate 142, study of TAS-102 in patients with metastatic colorectal cancer refractory to standard chemotherapies (RECOURSE), and Cancer and Leukemia Group B/Southwest Oncology Group 80405 trials. The analyzed outcomes included survival (life-years), quality-adjusted life-years (QALYs), and incremental cost-effectiveness ratios (ICERs). Ipilimumab with nivolumab was the most effective strategy (10.69 life-years and 9.25 QALYs for the third line; 10.69 life-years and 9.44 QALYs for the first line) in comparison with nivolumab (8.21 life-years and 6.76 QALYs for the third line; 8.21 life-years and 7.00 QALYs for the first line), trifluridine and tipiracil (0.74 life-years and 0.07 QALYs), and mFOLFOX6 and cetuximab (2.72 life-years and 1.63 QALYs). However, neither checkpoint inhibitor therapy was cost-effective in comparison with trifluridine and tipiracil (nivolumab ICER, $153,000; ipilimumab and nivolumab ICER, $162,700) or mFOLFOX6 and cetuximab (nivolumab ICER, $150,700; ipilimumab and nivolumab ICER, $158,700). This modeling analysis found that both single and dual checkpoint blockade could be significantly more effective for MSI-H/dMMR mCRC than chemotherapy, but they were not cost-effective, largely because of drug costs. Decreases in drug pricing and/or the duration of maintenance nivolumab could make ipilimumab and nivolumab cost-effective. Prospective clinical trials should be performed to explore the optimal duration of maintenance nivolumab.