First results from the phase 3 CheckMate 274 trial of adjuvant nivolumab vs placebo in patients who underwent radical surgery for high-risk muscle-invasive urothelial carcinoma (MIUC).

PD10-01 DISEASE-FREE SURVIVAL WITH LONGER FOLLOW-UP FROM THE CHECKMATE 274 TRIAL OF ADJUVANT NIVOLUMAB IN PATIENTS AFTER SURGERY FOR HIGH-RISK MUSCLE-INVASIVE UROTHELIAL CARCINOMA

658 Background: In the phase 3, randomized, double-blind CheckMate 274 trial, adjuvant NIVO demonstrated statistically significant and clinically meaningful disease-free survival (DFS) benefit vs PBO in pts with high-risk MIUC after radical surgery (RS) ± prior neoadjuvant cisplatin-based chemotherapy (NAC). With extended 3-y median follow-up, continued improvements in DFS were seen with NIVO vs PBO in the primary efficacy populations (intent-to-treat [ITT], tumor programmed death ligand 1 [PD-L1] expression ≥ 1%) and in pts with MIBC. Early trends in interim OS favored NIVO vs PBO in ITT and tumor PD-L1 ≥ 1% pts. Here we report additional efficacy outcomes for pts with MIBC. Methods: Pts were randomized 1:1 to NIVO 240 mg every 2 wk or PBO for ≤ 1 y of adjuvant treatment, stratified by tumor PD-L1 expression, nodal status, and prior NAC. Primary endpoints were DFS in ITT and tumor PD-L1 expression ≥ 1% pts. OS in ITT and PD-L1 ≥ 1% pts was a secondary endpoint. Analysis of MIBC pts was exploratory. MIBC OS data are from preplanned interim analyses of ITT and PD-L1 ≥ 1% pts. OS follow-up is ongoing as the prespecified statistical boundaries for significance in ITT and PD-L1 ≥ 1% pts were not crossed at the time of these analyses. Results: Of 709 randomized pts (ITT), 560 (79%) had MIBC (NIVO, n = 279; PBO, n = 281); 284 (51%) of MIBC pts had prior NAC. With median follow-up of 36.1 mo (ITT), DFS improvement with NIVO vs PBO was consistent between all pts with MIBC (hazard ratio [HR] 0.63) and those with (HR 0.58) and without prior NAC (HR 0.69; Table). For OS, HRs favored NIVO vs PBO in all pts with MIBC (HR 0.70) and the tumor PD-L1 ≥ 1% subgroup (HR 0.48), as well as in pts with MIBC with (HR 0.74) and without prior NAC (HR 0.67). Safety was consistent with previous data in ITT pts; no new safety signals were identified. Conclusions: With 3-y median follow-up, consistent benefit in DFS was observed with NIVO vs PBO in all MIBC pts and across prior NAC subgroups. The HR for OS favored NIVO in all MIBC pts, in those with PD-L1 ≥ 1%, and regardless of prior NAC status. These results continue to support adjuvant NIVO as a standard of care for high-risk MIUC and MIBC, potentially providing an opportunity for a curative outcome. Clinical trial information: NCT02632409 . NIVOn NIVOMedian(95% CI), mo PBOn PBOMedian(95% CI), mo HR (95% CI) DFS All MIBC 279 25.6 (19.2–41.8) 281 8.5 (7.3–13.7) 0.63 (0.51–0.78) With prior NAC 142 19.6 (15.6–48.2) 142 8.3 (5.6–11.2) 0.58 (0.43–0.79) No prior NAC 137 25.9 (19.2–51.5) 139 13.7 (7.8–22.1) 0.69 (0.50–0.94) OS All MIBC 279 NR (45.0–NE) 281 39.9 (29.8–52.1) 0.70 (0.55–0.90) PD-L1 ≥ 1% 113 NR (NE–NE) 117 37.6 (26.9–NE) 0.48 (0.29–0.77) With prior NAC 142 55.2 (41.8–NE) 142 40.2 (28.8–53.7) 0.74 (0.53–1.03) No prior NAC 137 NR (40.7–NE) 139 37.7 (28.7–65.2) 0.67 (0.47–0.95) NE, not estimable; NR, not reached.

LBA02-08 RESULTS FROM THE EXTENDED FOLLOW-UP IN PATIENTS WITH MUSCLE-INVASIVE BLADDER CANCER IN THE CHeckMATE 274 TRIAL

4585 Background: In the CheckMate 274 trial, disease-free survival (DFS) was significantly improved with nivolumab (NIVO) vs placebo (PBO) both in intent-to-treat (ITT) patients (pts) (hazard ratio [HR], 0.70; 98.22% confidence interval [CI], 0.55–0.90; P < 0.001) and in pts with tumor programmed death ligand 1 (PD-L1) expression ≥ 1% (HR, 0.55; 98.72% CI, 0.35–0.85; P < 0.001). We report results for the subgroup of pts with bladder cancer, the most predominant type of urothelial carcinoma. Methods: CheckMate 274 is a phase 3, randomized, double-blind trial of adjuvant NIVO vs PBO in high-risk muscle-invasive urothelial carcinoma (bladder, ureter, renal pelvis) after radical resection. Pts were randomized 1:1 to NIVO 240 mg intravenously every 2 weeks or PBO for ≤ 1 year of adjuvant treatment and stratified by nodal status, prior neoadjuvant cisplatin, and tumor PD-L1 expression. Pts had radical resection ± neoadjuvant chemotherapy and were at high risk of recurrence on final pathologic staging. Primary endpoints were DFS in ITT pts and in pts with PD-L1 ≥ 1%. Non–urothelial tract recurrence-free survival (NUTRFS) was a secondary endpoint, and distant metastasis-free survival (DMFS) was an exploratory endpoint. This exploratory analysis focused on the subgroup of pts with muscle-invasive bladder cancer (MIBC) after radical resection. Results: Of 709 randomized pts in the trial, 560 had MIBC (NIVO, n = 279; PBO, n = 281). With a minimum follow-up of 11.0 months, a DFS benefit was observed with NIVO vs PBO in these pts, regardless of tumor PD-L1 expression (Table). DFS probability at 12 months in all MIBC pts was 66% with NIVO and 45% with PBO. DFS was improved with NIVO vs PBO across subgroups according to age, sex, ECOG performance status, nodal status, and PD-L1 expression status. Improvement in NUTRFS and DMFS with NIVO vs PBO was also observed (Table). Grade 3–4 treatment-related adverse events occurred in 17% and 6% of pts in the NIVO and PBO arms, respectively. Conclusions: Improvement in DFS was observed with NIVO over PBO in pts with MIBC after radical resection regardless of tumor PD-L1 expression. The DFS benefit was observed in all prespecified subgroups. These results further support adjuvant NIVO as a standard-of-care treatment for pts with high-risk MIBC after radical resection ± neoadjuvant cisplatin-based chemotherapy. Clinical trial information: NCT02632409. [Table: see text]

491 Background: CheckMate 274 demonstrated a significant improvement in disease-free survival (DFS) with nivolumab (NIVO) versus placebo (PBO) both in the intent-to-treat population (hazard ratio [HR], 0.70; 98.22% confidence interval [CI], 0.55–0.90; P < 0.001) and in patients (pts) with tumor programmed death ligand 1 (PD-L1) expression ≥ 1% assessed by the tumor proportion score (TPS) (HR, 0.55; 98.72% CI, 0.35–0.85; P < 0.001). An exploratory subgroup analysis showed a trend toward a DFS benefit with NIVO in pts with TPS < 1% (0.82; 95% CI, 0.63–1.06). To further characterize the relationship between PD-L1 expression and NIVO efficacy, we report an analysis of DFS based on PD-L1 expression in both tumor and immune cells using the combined positive score (CPS). Methods: CheckMate 274 is a phase 3, randomized, double-blind, multicenter trial of NIVO versus PBO in pts with high-risk muscle-invasive urothelial carcinoma after radical surgery. Pts were randomized 1:1 to NIVO 240 mg or PBO every 2 weeks intravenously for 1 year of adjuvant treatment. The primary endpoints of the study are DFS in the intent-to-treat population and in pts with TPS ≥ 1%. The Dako PD-L1 IHC 28-8 pharmDx assay was used to evaluate TPS. CPS was determined retrospectively from previously stained immunohistochemistry slides using the CPS algorithm. CPS was calculated as the number of both PD-L1 positive tumor and immune cells divided by the number of viable tumor cells in the evaluable tumor area, multiplied by 100; TPS was similarly calculated with the number of PD-L1 positive tumor cells as the numerator. This analysis only included pts with both quantifiable CPS and TPS. Results: Of the 629 pts with quantifiable TPS and CPS, 249 (40%) had TPS ≥ 1% (NIVO, n = 124; PBO, n = 125), 380 (60%) had TPS < 1% (NIVO, n = 191; PBO, n = 189), 557 (89%) had CPS ≥ 1 (NIVO, n = 281; PBO, n = 276), and 72 (11%) had CPS < 1 (NIVO, n = 34; PBO, n = 38). Within TPS < 1% pts, 81% (n = 309) had CPS ≥ 1. The number of pts and the DFS outcomes in pts with TPS ≥ 1% and CPS ≥ 1 are shown in the Table. In pts with TPS < 1% who also had CPS ≥ 1, median DFS (95% CI) was 19.2 (15.6–33.4) months with NIVO versus 10.1 (8.2–19.4) months with PBO. The HR for NIVO versus PBO in these pts was 0.73 (95% CI, 0.54–0.99). Conclusions: This exploratory analysis of PD-L1 expression by CPS showed a higher proportion of pts with CPS ≥ 1 than TPS ≥ 1%, and that most pts with TPS < 1% had CPS ≥ 1. In the CPS ≥ 1 subgroup, median DFS with NIVO was more than double that with placebo. These results support the conclusion that pts with TPS < 1% also benefit from adjuvant NIVO. Clinical trial information: NCT02632409. [Table: see text]

Adjuvant immunotherapy in high-risk muscle-invasive urothelial cancer: an updated meta-analysis of randomized controlled trials

565 Background: NIVO has shown promise as an adjuvant treatment for MIUC. In the CheckMate 274 trial, NIVO achieved a significant improvement in disease-free survival compared to placebo in MIUC pts at high risk of recurrence following radical surgery. However, it is unclear how treatment decisions are made in the RW setting and what factors drive providers in selecting either NIVO or CHEMO as adjuvant treatment. We compared the baseline demographic and clinical characteristics of pts with MIUC who received adjuvant NIVO to those who received adjuvant platinum-based CHEMO in the RW setting. Methods: This retrospective medical chart review included pts diagnosed with stage II-IIIB MIUC who initiated treatment with NIVO or CHEMO within 120 days of radical resection between 9/1/2021 and 11/25/2022. Treating oncologists from a US nationally representative network abstracted pts’ data from electronic medical charts. Pts’ demographic and clinical characteristics were assessed. Results: Age, sex, and race were similar across cohorts (Table). Pts who received adjuvant NIVO (n = 158) vs CHEMO (n = 88) were more likely to have ECOG-PS≥ 2 at treatment initiation (24.1% vs 17.1%; P = 0.02), and more likely to receive PD-L1 testing (Not tested: 36.1% vs. 47.7%; P < 0.0001) and have PD-L1 expression levels ≥ 50% (13.9% vs 1.1%; P < 0.0001). A higher proportion of pts who received NIVO vs CHEMO had diabetes with chronic complications (15.8% vs 5.7%; P = 0.02) and hypertension (20.9% vs 6.8%; P = 0.004), and were determined to be cisplatin-ineligible (41.8% vs 25%; P = 0.007), predominately based on creatinine clearance (< 60 mL/min: 48.7% vs. 34.1%; P = 0.002) and poor PS (13.9% vs. 4.6%; P = 0.07); rheumatologic disease was less common among the NIVO cohort (1.9% vs 11.4%; P = 0.002). Conclusions: This RW analysis demonstrated that pts with MIUC who received adjuvant NIVO had greater baseline disease severity and comorbidities than those who received adjuvant CHEMO. These findings suggest that patient characteristics influence treatment selection of adjuvant therapy in this patient population, highlighting the need to adjust for baseline characteristics in future comparative analyses.[Table: see text]

LBA5 Background: Relapse after surgery for high-risk clear cell RCC (ccRCC) is associated with shortened life expectancy. Effective perioperative therapy to reduce this risk remains an unmet need. Adjuvant immune therapy is an attractive potential strategy for these pts. We conducted the KEYNOTE-564 trial to evaluate pembro vs placebo as adjuvant therapy for pts with RCC. Methods: KEYNOTE-564 is a phase III multicenter trial of pembro vs placebo in pts with histologically confirmed ccRCC, with intermediate-high risk (pT2, Gr 4 or sarcomatoid, N0 M0; or pT3, any Gr, N0 M0), high risk (pT4, any Gr, N0 M0; or pT any stage, any Gr, N+ M0), or M1 NED (no evidence of disease after primary tumor + soft tissue metastases completely resected ≤1 year from nephrectomy) (Leibovich et al, 2003; Fuhrman et al, 1982). Pts had undergone surgery ≤12 wks prior to randomization; had no prior systemic therapy; had ECOG PS 0 or 1. Study treatment was given for up to 17 cycles (≈1 yr). The primary endpoint was disease-free survival (DFS) per investigator assessment in all randomized pts (ITT population). Overall survival (OS) was a key secondary endpoint. Safety/tolerability were secondary endpoints, assessed in all treated pts. Results: Between Jun 30, 2017 and Sept 20, 2019, 994 pts were randomized 1:1 to pembro (n=496) or placebo (n=498). As of data cutoff date of Dec 14, 2020, median (range) follow-up, defined as time from randomization to data cutoff, was 24.1 (14.9−41.5) mo. No pts remain on study treatment. Baseline characteristics were generally balanced between arms. At first prespecified interim analysis, the primary endpoint of DFS was met (median not reached [NR] for both arms, HR 0.68, 95% CI 0.53−0.87; P=0.0010 [one-sided]). The estimated DFS rate at 24 mo was 77.3% with pembro vs 68.1% with placebo. Overall, DFS benefit was consistent across subgroups. A total of 51 OS events were observed (18 in the pembro arm, 33 in the placebo arm). Median OS was NR for both arms (HR 0.54, 95% CI 0.30−0.96; P=0.0164 [one-sided]); the p-value did not cross the statistical hypothesis testing boundary. The estimated OS rate at 24 mo was 96.6% with pembro vs 93.5% with placebo. 470 pts (96.3%) and 452 pts (91.1%) experienced ≥1 all-cause adverse events (AEs) with pembro vs placebo, respectively. Grade 3-5 all-cause AEs occurred in 158 pts (32.4%) with pembro and 88 pts (17.7%) with placebo. No deaths related to pembro occurred. Conclusions: Pembro demonstrated a statistically significant and clinically meaningful improvement in DFS vs placebo in pts with intermediate-high, high risk or M1 NED RCC. Additional follow-up is planned for the key secondary endpoint of OS. KEYNOTE-564 is the first positive phase III study with a checkpoint inhibitor in adjuvant RCC, and these results support pembro as a potential new standard of care for pts with RCC in the adjuvant setting. Clinical trial information: NCT03142334.

LBA8010 Background: The phase 3 CheckMate 77T study demonstrated statistically significant and clinically meaningful improvement in EFS with perioperative NIVO vs PBO in pts with resectable NSCLC. pCR rates were also improved. Here, we report updated EFS, OS from the first prespecified interim analysis, and exploratory biomarker analyses. Methods: Pts with resectable stage IIA–IIIB (N2; AJCC v8) NSCLC were randomized 1:1 to neoadjuvant (neoadj) NIVO + chemotherapy (chemo) Q3W (up to 4 cycles [cyc]) followed by adjuvant (adj) NIVO Q4W (up to 13 cyc) or neoadj PBO + chemo Q3W (up to 4 cyc) followed by adj PBO Q4W (up to 13 cyc). The primary endpoint was EFS per BICR. Secondary endpoints included pCR, OS, and safety. Exploratory analyses included efficacy by pCR status, presurgery ctDNA clearance (CL), and tumor genomic alterations. Results: At a median follow-up of 41.0 mo (database lock, 16 Dec 2024), NIVO continued to provide EFS benefit vs PBO (HR [95% CI], 0.61 [0.46–0.80]; 30-mo EFS rates, 61% vs 43%) in all randomized pts and regardless of disease stage, tumor histology, or PD-L1 expression (Table). EFS from surgery (HR [95% CI]) continued to favor NIVO vs PBO in pts with pCR (0.90 [0.19–4.15]) or without (w/o; 0.72 [0.50–1.05]). In biomarker-evaluable pts (NIVO, 98; PBO, 92), pts with ctDNA CL had greater EFS benefit (assessed from randomization) vs pts w/o (HR [95% CI]: NIVO, 0.41 [0.20–0.86]; PBO, 0.62 [0.31–1.22]); pts with ctDNA CL with or w/o pCR had improved EFS vs pts w/o ctDNA CL and pCR (data to be presented). EFS (HR [95% CI]) favored NIVO vs PBO in pts with tumor genomic alterations ( KRAS , and/or STK11 , and/or KEAP1 mutations; 0.63 [0.32–1.23]) or w/o (0.65 [0.39–1.10]). Higher ctDNA CL and pCR rates were seen with NIVO vs PBO regardless of mutation status; additional efficacy and ctDNA outcomes will be presented. At the first prespecified interim OS analysis, NIVO showed a trend of OS improvement vs PBO in all randomized pts (HR [97.63% CI], 0.85 [0.58–1.25]; median OS, not reached in both tx arms; 30-mo OS rates, 78% vs 72%). Safety outcomes were consistent with previous reports. Conclusions: In this update, perioperative NIVO continued to show long-term EFS benefit and a favorable OS trend vs PBO in pts with resectable NSCLC; no new safety signals were observed. In exploratory analyses, presurgery ctDNA CL was associated with EFS benefit. EFS favored NIVO vs PBO regardless of KRAS , STK11 , and KEAP1 mutation status. Clinical trial information: NCT04025879 . All pts Stage II Stage III Squamous Non-squamous PD-L1 < 1% PD-L1 ≥ 1% NIVO (N = 229) vs PBO(N = 232) NIVO (n = 80) vs PBO(n = 81) NIVO (n = 149) vs PBO(n = 149) NIVO (n = 116) vs PBO(n = 118) NIVO (n = 113) vs PBO(n = 114) NIVO (n = 93) vs PBO(n = 93) NIVO (n = 128) vs PBO(n = 128) Median EFS, mo 46.6 vs 16.9 NR vs NR 42.1 vs 13.4 NR vs 16.4 40.1 vs 16.9 40.1 vs 19.8 46.6 vs 15.1 HR (95% CI) 0.61(0.46–0.80) 0.77(0.46–1.30) 0.54(0.39–0.74) 0.53(0.35–0.80) 0.69 (0.48–1.00) 0.79(0.52–1.21) 0.53(0.36–0.76)

LBA8007 Background: In CheckMate 77T, perioperative NIVO showed statistically significant EFS improvement vs neoadjuvant (neoadj) chemo followed by adjuvant (adj) placebo (PBO) in pts with stage (stg) II or III resectable NSCLC. We report clinical outcomes by baseline (BL) stg III N2 status, a subgroup with poor historical 5 y survival (26%–36%; Goldstraw J Thorac Oncol 2016). Methods: Adults with resectable stg IIA–IIIB (N2; AJCC v8) NSCLC were randomized to neoadj NIVO 360 mg Q3W + chemo (4 cycles [cyc]) followed by adj NIVO 480 mg Q4W (13 cyc) or neoadj PBO Q3W + chemo (4 cyc) followed by adj PBO Q4W (13 cyc). Primary endpoint: EFS per BICR. Exploratory analysis: efficacy and safety in pts with BL clinical stg III N2 or non N2 disease (dz). Results: BL characteristics were generally similar between pts with stg III N2 (NIVO, 91; PBO, 90) and non N2 dz (55; 57), and between treatment (tx) arms, except a higher percent of pts with N2 dz had NSQ histology and ECOG PS 0 (both arms). Pts with N2 dz had improved EFS with NIVO vs PBO (HR 0.46; 1 y EFS 70% vs 45%) and higher pCR (22.0% vs 5.6%; median f/u 25.4 mo; Table). Pts with non N2 also had EFS benefit with NIVO vs PBO (HR 0.60; 1 y EFS 74% vs 62%) and higher pCR (25.5% vs 5.3%; Table). Surgical feasibility was similar between pts with N2 and non N2 dz and numerically higher with NIVO vs PBO. Of pts with N2 dz, 77% (NIVO) vs 73% (PBO) had definitive surgery (pneumonectomy 1% vs 14%; R0 resection 86% vs 86%); of pts with non N2 dz, 82% vs 79% had definitive surgery (pneumonectomy 13% vs 9%; R0 resection 84% vs 87%). Tumor downstaging postsurgery was seen in most pts with stg III dz and was deeper with NIVO vs PBO: 61% vs 50% (N2; 33% vs 14% to ypT0), 87% vs 76% (non N2; 27% vs 11% to ypT0). Of all pts with stg III dz, nodal downstaging postsurgery was 52% (NIVO) vs 45% (PBO); 46% vs 36% to ypN0. Grade 3–4 TRAEs occurred in 34% (NIVO) and 26% (PBO) of pts with N2; 29% and 21% of pts with non N2 dz. Conclusions: In this exploratory analysis, perioperative NIVO showed clinical benefit vs PBO in pts with stg III NSCLC, regardless of N2 status. Over half of pts with stg III dz had nodal downstaging with NIVO; majority downstaged to ypN0. This first comprehensive analysis by nodal status among pts with stg III dz from a global phase 3 study of perioperative immunotherapy further supports perioperative NIVO as a tx option for pts with resectable NSCLC. Clinical trial information: NCT04025879 . [Table: see text]

5000 Background: Radical surgery ± cisplatin-based neoadjuvant chemo (NAC) is the mainstay treatment (tx) for MIUC, with no conclusive level 1 evidence for adjuvant chemo (AC). Here we present the primary analysis from IMvigor010, a global, open-label, multicenter, randomized trial of adjuvant atezo (anti–PD-L1; approved in metastatic UC [mUC] settings) in pts with MIUC at high risk of recurrence following primary resection. Methods: Pts with MIUC (bladder, upper tract [UT]), ECOG PS 0-2 and resected tissue for PD-L1 testing on immune cells (IC; VENTANA SP142 assay) were enrolled ≤ 14 wks after radical cystectomy/nephroureterectomy with lymph node (LN) dissection. Pathologic stage: 1) ypT2-4a or ypN+ if pts had NAC or 2) pT3-4a or pN+ if pts did not have NAC. No postsurgical radiation or AC was allowed; if no NAC was given, pts must have been ineligible for or declined cisplatin-based AC. Pts were randomized 1:1 to atezo 1200 mg IV q3w or obs for 16 cycles or 1 y (stratification factors: no. of LNs resected, pathologic nodal status, pathologic tumor stage, PD-L1 status, prior NAC). Disease-free survival (DFS) was the primary endpoint (EP). Final DFS, first interim overall survival (OS; secondary EP) and safety are reported. Results: The ITT population included 809 pts (median follow-up, 21.9 mo). In the atezo and obs arms, respectively, 48% and 47% had NAC; 7% and 6% had UTUC as primary disease; 48% each had LN+ disease. DFS and OS are in Table. Baseline prognostic/clinical factors did not influence DFS tx benefit; stratified HR was 0.81 (95% CI: 0.63, 1.05) in IC0/1 pts (PD-L1 < 5%; n = 417) and 1.01 (0.75, 1.35) in IC2/3 pts (PD-L1 ≥ 5%; n = 392). 16% of atezo-treated pts had a tx-related G3-4 AE. Skin and gastrointestinal toxicities most commonly led to tx discontinuation. Conclusions: IMvigor010, the first phase 3 adjuvant study of a checkpoint inhibitor in MIUC, did not meet its primary EP of DFS. More tx discontinuation due to AEs was seen vs mUC studies. Safety was generally consistent with previous studies. Clinical trial information: NCT02450331 . [Table: see text]

549 Background: MA.17 evaluated letrozole (LET) or placebo (PLAC) after 5 years of tamoxifen (Tam) and showed [median follow-up 30 months (mos)] significant improvement in disease-free survival (DFS) for LET [hazard ratio (HR) 0.57, p = 0.00008]. The trial was unblinded and PLAC patients (pts) were offered LET. An ITT analysis of all outcomes, before and after unblinding, based on the original randomization was performed. Methods: A stratified log-rank test was used to compare DFS, distant (D)DFS, overall survival (OS) and incidence of contra-lateral breast cancer (CBC). The Cox regression model used baseline stratification variables and two prespecified factors, menopausal status at the start of Tam and time on Tam. Subgroup analyses for DFS and OS were performed for the two prespecified subsets. All p-values were two-sided Results: 5187 pts were randomized at baseline and, at unblinding, 1655 of 2268 PLAC pts accepted LET. At median follow-up of 54 mos (range,16–86) 363 recurrences or CBC’s (144 LET and 219 PLAC) occurred; 118 LET and 176 PLAC pts had recurrent disease and 26 LET and 43 PLAC pts had CBC. 4 year DFS was 94.3% (LET) and 91.4% (PLAC) (HR 0.64; 95% CI, 0.52 - 0.79; p = 0.00002). Corresponding 4 year DDFS was 96.2% and 94.9% (HR 0.76; 0.58–0.99; p = 0.041). 4 year OS was 95.0% (LET) and 95.1% (PLAC) (HR 1.00; 0.78–1.28; p = 0.99). LET was equally effective in node +ve and -ve pts (i.e., similar HRs) in DFS. OS was not significantly different for LET and PLAC in any subgroup. The annual rate of CBC was 0.29% LET (0.18–0.40) and 0.47% PLAC (0.34–0.61); HR 0.61 (0.38–0.98) p = 0.037. 255 pts had died as of the data cut-off (128 LET and 127 PLAC). Conclusions: In this ITT analysis, pts originally randomized to LET within 3 months of stopping Tam did better than PLAC pts in DFS, DDFS and CBC, despite 73% of PLAC pts crossing to LET after unblinding. This highlights the strong beneficial effect of extended adjuvant therapy with LET. [Table: see text]

PLLBA-01 PEMBROLIZUMAB (PEMBRO) VS PLACEBO AS POST NEPHRECTOMY ADJUVANT THERAPY FOR PATIENTS (pts) WITH RENAL CELL CARCINOMA (RCC): RANDOMIZED, DOUBLE-BLIND, PHASE 3 KEYNOTE-564 STUDY

Long-term outcomes from the randomized, double-blind, placebo (PBO)-controlled, phase 3 imerge trial of imetelstat (IME) for lower-risk myelodysplastic syndromes (LR-MDS)

318 Background: NIVO + chemo demonstrated clinically meaningful improvement in overall survival (OS) and an acceptable safety profile vs chemo in previously untreated Chinese pts from CheckMate 649, consistent with the overall study population with advanced GC/GEJC/EAC. 1L NIVO + chemo is approved for advanced GC/GEJC/EAC in multiple countries, including China. We report 4-yr results of NIVO + chemo vs chemo in Chinese pts from CheckMate 649. Methods: Adults with previously untreated, unresectable advanced or metastatic, non-HER2+ GC/GEJC/EAC were enrolled regardless of programmed death ligand 1 (PD-L1) expression. Randomized pts received NIVO (360 mg Q3W or 240 mg Q2W) + chemo (XELOX Q3W or FOLFOX Q2W), NIVO + ipilimumab, or chemo. Dual primary endpoints for NIVO + chemo vs chemo were OS and progression-free survival (PFS) by blinded independent central review (BICR) in pts with PD-L1 combined positive score (CPS) ≥ 5. Results: 208 Chinese pts were randomized to NIVO + chemo or chemo. At 49-month (mo) minimum follow-up, NIVO + chemo continued to demonstrate OS and PFS benefit vs chemo in pts with PD-L1 CPS ≥ 5 and in all randomized pts (Table). The 4-yr OS rate was 25% with NIVO + chemo vs 11% with chemo in pts with PD-L1 CPS ≥ 5 and 21% vs 9% in all randomized pts. Objective response rate (ORR; 95% CI) per BICR in pts with PD-L1 CPS ≥ 5 who had measurable lesions at baseline was 68% (56–79) with NIVO + chemo vs 48% (36–60) with chemo; corresponding ORR in all randomized pts was 66% (55–76) and 45% (35–56). Responses were more durable with NIVO + chemo vs chemo both in pts with PD-L1 CPS ≥ 5 (median duration of response [mDOR; 95% CI] 12.5 mo [7.2–23.4] vs 6.9 mo [3.9–8.5]) and in all randomized pts (mDOR [95% CI] 12.5 mo [7.2–17.7] vs 5.6 mo [4.4–8.3]). No new safety signals were identified (Table). Conclusions: After 4 yrs of follow-up, NIVO + chemo continued to demonstrate clinically meaningful survival benefit and more durable responses vs chemo in Chinese pts, with an acceptable safety profile. These results are consistent with previous reports and with the overall study population with advanced GC/GEJC/EAC and further support NIVO + chemo as a standard 1L treatment option for Chinese pts. Clinical trial information: NCT02872116 . [Table: see text]