Peters, Walter R.

LBA1 Background: Standard adjuvant chemotherapy of stage III colon cancer consists of a fluoropyrimidine plus oxaliplatin. In patients (pts) with stage III colon cancer and deficient mismatch repair (dMMR), the benefit of an immune checkpoint inhibitor combined with adjuvant chemotherapy is unknown. The phase III ATOMIC trial (NCT02912559) was conducted to determine whether atezolizumab (atezo), an anti-PD-L1 antibody, can improve pt outcomes when added to adjuvant 5-fluorouracil, leucovorin plus oxaliplatin (mFOLFOX6) in pts with stage III dMMR tumors. Methods: We conducted an NCI-sponsored, multicenter and randomized phase III trial in pts with surgically resected stage III dMMR colon adenocarcinoma (any T, N 1,2 M 0 ). Pts, age > 12 years (yr), were accrued at NCTN sites and the German AIO. Tumor dMMR was determined by local immunohistochemistry and centrally verified. Pts were randomized 1:1 to mFOLFOX6 plus atezo (840 mg IV q2 weeks) for 12 cycles (6 months)[mo] followed by atezo monotherapy for 13 cycles (12 mo total) versus mFOLFOX6 alone for 12 cycles. Randomization stratification factors were N-stage (N 1 /N 1c vs N 2 ), T-stage (T 1 -T 3 vs T 4 ) and site (proximal vs distal). The primary endpoint was disease-free survival (DFS); secondary endpoints were overall survival and adverse event (AE) profile (CTCAE, PRO-CTCAE). Primary efficacy analysis was done in the intent-to-treat population; DFS was compared by arm (stratified log-rank test). Hazard ratio (HR) and 95% confidence interval (CI) were calculated using a stratified Cox model; 3-yr DFS was determined by Kaplan-Meier method. Among 700 pts., 165 DFS events with two interim analyses (50% , 75% of events) yielded 90% power to detect HR 0.6 (3-yr DFS 75% vs. 84.2%) assuming exponential survival and 1-sided alpha (0.025). Results: From 9/2017 to 1/2023, 712 pts were randomized (1 pediatric) to either atezo plus mFOLFOX6 (n= 355; atezo arm) or mFOLFOX6 (n= 357). Median pt age was 64 yr. 55.1% were female. Among tumors, 83.8% were proximal, 46.1% were clinical low risk (T 1-3 N 1 ) and 53.9% high risk (T 4 and/or N 2 ). At the second interim analysis, median pt follow-up was 37.2 mo (interquartile range, 24.2 to 55.5) and 124 DFS events were observed. Three-year DFS was 86.4 % (95% CI, 81.8 to 89.9) in the atezo arm and 76.6 % (95% CI, 71.3 to 81.0) in the mFOLFOX6 arm (HR, 0.50; 95% CI, 0.35 to 0.72). Stratified log-rank p-value was <0.0001, crossing the pre-specified efficacy boundary of 0.009. Efficacy for the atezo arm was consistent across subgroups, including pts >70 yr and low- and high-risk groups. Treatment-related > grade 3 AEs occurred in 71.7 % of pts in the atezo arm vs 62.1 % in the mFOLFOX6 arm. Conclusion: The addition of atezolizumab to mFOLFOX6 significantly improved DFS and should be considered the new adjuvant standard of care for patients with dMMR stage III colon cancer. Support: U10CA180821, U10CA180882, U24CA196171; Genentech, a member of the Roche group; https://acknowledgments.alliancefound.org. Clinical trial information: NCT02912559 .

e15169 Background: In metastatic colorectal cancer with deficient DNA mismatch repair (dMMR), anti-PD-1 antibody monotherapy produced high tumor response rates and extended progression-free survival compared to lack of benefit for cancers with proficient MMR. In an ongoing phase III randomized trial, we will determine if the addition of the anti-PD-L1 antibody, atezolizumab (Genentech), to adjuvant FOLFOX can improve patient disease-free survival (DFS) vs FOLFOX alone in patients with stage III colon cancers with dMMR. By blocking the PD-1/PD-L1 interaction, atezolizumab may activate T cells, thereby, restoring their ability to detect and attack tumor cells. Limited data suggest that FOLFOX may increase intratumoral cytotoxic CD8+ T cells that could serve as ‘immune priming'. Methods: Patients with curatively resected stage III colon carcinomas with evidence of dMMR are randomized to modified FOLFOX6 for 6 months (12 cycles) alone (control arm) or combined with atezolizumab (840 mg IV q2 wk) with continuation of the antibody as monotherapy for an additional 6 months (total duration of 12 months) [experimental arm]. Patients will be stratified by T, N stage and tumor sidedness. Local testing for MMR proteins is allowed. Atezolizumab must begin by/with cycle 2. One cycle of FOLFOX is allowed pre-registration. The targeted accrual goal of 700 patients and 165 disease-free survival (DFS) events will provide 90% power to detect an effect size expressed as hazard ratio of 0.6 for the primary endpoint of DFS at two-sided alpha of 0.05. Interim analyses are planned at 50% and 75% of events. Secondary endpoints include overall survival, treatment tolerability, and quality of life. Results: This study is being conducted by the Alliance for Clinical Trials in Oncology, was approved by NCI CTEP and activated in 09/2017. The study is actively accruing and, as of 02/11/2019, 152 patients are enrolled. We are actively exploring an international collaboration. Conclusions: This is a current clinical trial in progress. Clinical trial information: NCT02912559.

TPS3630 Background: In metastatic colorectal cancer with deficient DNA mismatch repair (MMR), anti-PD-1 antibody monotherapy produced high tumor response rates and extended progression-free survival compared to lack of benefit for proficient MMR tumors (Le, M, et al, NEJM 2016). We propose a phase III randomized trial to determine if the addition of the anti-PD-L1 antibody, atezolizumab (Genentech™), to adjuvant FOLFOX can improve patient disease-free survival (DFS) vs FOLFOX alone in patients with stage III colon cancers with dMMR or microsatellite instability (MSI). By blocking the PD-1/PD-L1 interaction, atezolizumab may activate T cells, thereby, restoring their ability to detect and attack tumor cells. Limited data suggest that FOLFOX may increase intratumoral cytotoxic CD8+ T cells that may serve as ‘immune priming.’ Methods: Patients with curatively resected stage III colon carcinomas with evidence of dMMR or MSI will be randomized to modified FOLFOX6 for 6 months (12 cycles) alone or combined with atezolizumab (840 mg IV q2 wk) continued as monotherapy for an additional 6 months (total duration of 12 months). Patients will be stratified by T, N stage and tumor sidedness. Local testing for MSI or MMR proteins is allowed. Atezolizumab must begin by/with cycle 2. The targeted accrual goal of 700 patients provides 90% power to detect an effect size expressed as hazard ratio of 0.6 for the primary endpoint DFS at two-sided alpha of 0.05. Interim analyses are planned at 50% and 75% of events. Secondary endpoints include overall survival, treatment tolerability, and quality of life. This study will be conducted by the Alliance for Clinical Trials in Oncology. The protocol has been approved by NCI CTEP and is expected to be activated in mid 2017. Clinical trial information: NCT02912559.

Objective: To determine the disease-free survival (DFS) and recurrence after the treatment of patients with rectal cancer with open (OPEN) or laparoscopic (LAP) resection. Background: This randomized clinical trial (ACOSOG [Alliance] Z6051), performed between 2008 and 2013, compared LAP and OPEN resection of stage II/III rectal cancer, within 12 cm of the anal verge (T1-3, N0-2, M0) in patients who received neoadjuvant chemoradiotherapy. The rectum and mesorectum were resected using open instruments for rectal dissection (included hybrid hand-assisted laparoscopic) or with laparoscopic instruments under pneumoperitoneum. The 2-year DFS and recurrence were secondary endpoints of Z6051. Methods: The DFS and recurrence were not powered, and are being assessed for superiority. Recurrence was determined at 3, 6, 9, 12, and every 6 months thereafter, using carcinoembryonic antigen, physical examination, computed tomography, and colonoscopy. In all, 486 patients were randomized to LAP (243) or OPEN (243), with 462 eligible for analysis (LAP = 240 and OPEN = 222). Median follow-up is 47.9 months. Results: The 2-year DFS was LAP 79.5% (95% confidence interval [CI] 74.4–84.9) and OPEN 83.2% (95% CI 78.3–88.3). Local and regional recurrence was 4.6% LAP and 4.5% OPEN. Distant recurrence was 14.6% LAP and 16.7% OPEN. Disease-free survival was impacted by unsuccessful resection (hazard ratio [HR] 1.87, 95% CI 1.21–2.91): composite of incomplete specimen (HR 1.65, 95% CI 0.85–3.18); positive circumferential resection margins (HR 2.31, 95% CI 1.40–3.79); positive distal margin (HR 2.53, 95% CI 1.30–3.77). Conclusion: Laparoscopic assisted resection of rectal cancer was not found to be significantly different to OPEN resection of rectal cancer based on the outcomes of DFS and recurrence.