Frankel, Wendy L.

3626 Background: For patients (pts) with dMMR stage III colon cancer, the addition of atezolizumab (atezo) to adjuvant 5-fluorouracil, leucovorin plus oxaliplatin (mFOLFOX6) significantly improved disease-free survival in ATOMIC (NCT02912559). Here we present HRQOL data. Methods: Pts with surgically resected stage III dMMR colon cancer were randomized (1:1) to receive mFOLFOX6 + atezo (840 mg IV q2 weeks) for 12 cycles (6 months [mo]) followed by atezo monotherapy for 13 cycles (12 mo total) versus mFOLFOX6 for 12 cycles. HRQOL was an exploratory endpoint measured using the FACT-C (includes FACT-G), FACT/GOG-NTX, EQ5D-5L, and PRO-CTCAE. Optional participation was by paper surveys at trial registration, prior to treatment cycles 4 and 7, and at 6, 12, and 36 mo after registration. Mean changes from baseline (BL) were compared between treatment arms using general linear mixed models (negative mean changes indicate worsening). At 6 mo, a two-sided 95% confidence interval excluding a difference of 1.9 points (FACT/GOG-NTX) and 6 points (FACT-C Trial Outcome Index [TOI]) favoring the mFOLFOX6 arm would indicate non-inferiority of the addition of atezo. Rates of side effect bother (FACT-G item GP5) and pt-reported adverse events (AEs) by PRO-CTCAE (composite scores, baseline adjusted) were compared using Fisher’s exact tests. Results: Of 712 randomized pts, 581 (285 atezo+mFOLFOX6; 296 mFOLFOX6) consented to participate in the survey. Pts completed 2398/3021 (79%) of expected surveys across all time points (1218/1489 [82%] atezo+mFOLFOX6; 1180/1532 [77%] mFOLFOX6). The difference in mean changes from BL between arms indicated non-inferiority of the addition of atezo at 6 mo (table); differences remained small at 12 and 36 mo. No significant differences in mean changes from BL between arms were found at 6, 12, or 36 mo for any scale. At 6 mo, 16% vs 20% of pts in each arm reported at least “quite a bit” of side effect bother (p=0.34), favoring atezo. Across cycles, atezo was associated with higher rates of pt-reported itchy skin (62% vs 48%), cough (53% vs 43%), and shortness of breath (51% vs 41%) [all p<0.05]. Conclusions: Addition of atezo to mFOLFOX6 slightly increases pt-reported AEs, but its effect on HRQOL is minimal and not clinically meaningful. Results support tolerability of atezo+mFOLFOX6 as standard of care adjuvant treatment for pts with dMMR stage III colon cancer. Support: UG1CA189823, U10CA180821, U10CA180882; Genentech, a member of the Roche group; https://acknowledgments.alliancefound.org. Clinical trial information: NCT02912559 . Scale Mo Mean change from BL – atezo+mFOLFOX6 Mean change from BL – mFOLFOX6 Diff (95% CI) FACT/GOG-NTX 6 -10.0 -10.6 0.6 (-0.8, 2.1) 12 -8.0 -9.4 1.4 (-0.2, 2.9) 36 -7.2 -6.9 -0.4 (-2.1, 1.4) FACT-C TOI 6 -4.1 -2.5 -1.6 (-3.7, 0.6) 12 2.1 1.8 0.3 (-1.9, 2.6) 36 0.7 1.8 -1.1 (-3.7, 1.5)

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 .

TPS4204 Background: The role of neoadjuvant chemotherapy in resectable pancreatic cancer has yet to be defined. Recent phase II trial results demonstrate a median overall survival time (mOS) of only 22.4 months after treatment with perioperative modified FOLFIRINOX (mFOLFIRINOX) with 36% not reaching surgery due to disease progression during neoadjuvant therapy. While potential benefits and shortcomings of neoadjuvant chemotherapy have been well documented, to date, no phase III trial has directly compared a perioperative versus an adjuvant chemotherapy strategy in resectable pancreatic cancer. Alliance for Clinical Trials in Oncology A021806 is an actively accruing randomized controlled phase III trial evaluating the efficacy of perioperative chemotherapy with mFOLFIRINOX in patients with resectable pancreatic cancer. Methods: To qualify for enrollment, patients must have biopsy-proven localized resectable pancreatic adenocarcinoma as defined by the National Comprehensive Cancer Network. Patients must have good performance status (ECOG 0 or 1) and be candidates to receive mFOLFIRINOX treatment. All patients enrolled undergo central radiologic eligibility review for quality control and are then randomized to either Arm 1 which consists of 8 cycles of neoadjuvant mFOLFIRINOX followed by 4 cycles of adjuvant mFOLFIRINOX or Arm 2 which includes upfront surgery followed by 12 cycles of adjuvant mFOLFIRINOX. The primary endpoint of the trial is overall survival with secondary endpoints evaluating disease-free survival, margin-negative resection rate, surgical complications, and chemotherapeutic adverse events. Additional correlative endpoints include quality of life and radiomic imaging assessments. A total enrollment of 352 patients is planned from the US and Canada; current enrollment for this trial is at 145 patients. An OS interim analysis will be performed when 50% of the events (124) are observed combining the two arms. If the trial continues after interim analysis, the final OS analysis will be performed with a total of 248 events (combined arms). If the Cox model (stratified by tumor location and ECOG PS) comparing OS between arms produces a one-sided p-value < 0.05, then we will conclude that the OS of the perioperative therapy arm is superior to adjuvant therapy. The Alliance A021806 phase III trial aims to define a new standard of care for patients with resectable pancreatic cancer. Clinical trial information: NCT04340141 .

Importance National guidelines endorse treatment with neoadjuvant therapy for borderline resectable pancreatic ductal adenocarcinoma (PDAC), but the optimal strategy remains unclear. Objective To compare treatment with neoadjuvant modified FOLFIRINOX (mFOLFIRINOX) with or without hypofractionated radiation therapy with historical data and establish standards for therapy in borderline resectable PDAC. Design, Setting, and Participants This prospective, multicenter, randomized phase 2 clinical trial conducted from February 2017 to January 2019 among member institutions of National Clinical Trials Network cooperative groups used standardized quality control measures and included 126 patients, of whom 70 (55.6%) were registered to arm 1 (systemic therapy; 54 randomized, 16 following closure of arm 2 at interim analysis) and 56 (44.4%) to arm 2 (systemic therapy and sequential hypofractionated radiotherapy; all randomized before closure). Data were analyzed by the Alliance Statistics and Data Management Center during September 2021. Interventions Arm 1: 8 treatment cycles of mFOLFIRINOX (oxaliplatin, 85 mg/m 2 ; irinotecan, 180 mg/m 2 ; leucovorin, 400 mg/m 2 ; and infusional fluorouracil, 2400 mg/m 2 ) over 46 hours, administered every 2 weeks. Arm 2: 7 treatment cycles of mFOLFIRINOX followed by stereotactic body radiotherapy (33-40 Gy in 5 fractions) or hypofractionated image-guided radiotherapy (25 Gy in 5 fractions). Patients without disease progression underwent pancreatectomy, which was followed by 4 cycles of treatment with postoperative FOLFOX6 (oxaliplatin, 85 mg/m 2 ; leucovorin, 400 mg/m 2 ; bolus fluorouracil, 400 mg/m 2 ; and infusional fluorouracil, 2400 mg/m 2 over 46 hours). Main Outcomes and Measures Each treatment arm’s 18-month overall survival (OS) rate was compared with a historical control rate of 50%. A planned interim analysis mandated closure of either arm for which 11 or fewer of the first 30 accrued patients underwent margin-negative (R0) resection. Results Of 126 patients, 62 (49%) were women, and the median (range) age was 64 (37-83) years. Among the first 30 evaluable patients enrolled to each arm, 17 patients in arm 1 (57%) and 10 patients in arm 2 (33%) had undergone R0 resection, leading to closure of arm 2 but continuation to full enrollment in arm 1. The 18-month OS rate of evaluable patients was 66.7% (95% CI, 56.1%-79.4%) in arm 1 and 47.3% (95% CI 35.8%-62.5%) in arm 2. The median OS of evaluable patients in arm 1 and arm 2 was 29.8 (95% CI, 21.1-36.6) months and 17.1 (95% CI, 12.8-24.4) months, respectively. Conclusions and Relevance This randomized clinical trial found that treatment with neoadjuvant mFOLFIRINOX alone was associated with favorable OS in patients with borderline resectable PDAC compared with mFOLFIRINOX treatment plus hypofractionated radiotherapy; thus, mFOLFIRINOX represents a reference regimen in this setting. Trial Registration ClinicalTrials.gov Identifier: NCT02839343

PURPOSE To evaluate the use of early assessment of chemotherapy responsiveness by positron emission tomography (PET) imaging to tailor therapy in patients with esophageal and esophagogastric junction adenocarcinoma. METHODS After baseline PET, patients were randomly assigned to an induction chemotherapy regimen: modified oxaliplatin, leucovorin, and fluorouracil (FOLFOX) or carboplatin-paclitaxel (CP). Repeat PET was performed after induction; change in maximum standardized uptake value (SUV) from baseline was assessed. PET nonresponders (< 35% decrease in SUV) crossed over to the alternative chemotherapy during chemoradiation (50.4 Gy/28 fractions). PET responders (≥ 35% decrease in SUV) continued on the same chemotherapy during chemoradiation. Patients underwent surgery at 6 weeks postchemoradiation. Primary end point was pathologic complete response (pCR) rate in nonresponders after switching chemotherapy. RESULTS Two hundred forty-one eligible patients received Protocol treatment, of whom 225 had an evaluable repeat PET. The pCR rates for PET nonresponders after induction FOLFOX who crossed over to CP (n = 39) or after induction CP who changed to FOLFOX (n = 50) was 18.0% (95% CI, 7.5 to 33.5) and 20% (95% CI, 10 to 33.7), respectively. The pCR rate in responders who received induction FOLFOX was 40.3% (95% CI, 28.9 to 52.5) and 14.1% (95% CI, 6.6 to 25.0) in responders to CP. With a median follow-up of 5.2 years, median overall survival was 48.8 months (95% CI, 33.2 months to not estimable) for PET responders and 27.4 months (95% CI, 19.4 months to not estimable) for nonresponders. For induction FOLFOX patients who were PET responders, median survival was not reached. CONCLUSION Early response assessment using PET imaging as a biomarker to individualize therapy for patients with esophageal and esophagogastric junction adenocarcinoma was effective, improving pCR rates in PET nonresponders. PET responders to induction FOLFOX who continued on FOLFOX during chemoradiation achieved a promising 5-year overall survival of 53%.

377 Background: Neoadjuvant therapy has been associated with a median overall survival (OS) of 18 – 23 months (mo) in patients (pts) with BR pancreatic ductal adenocarcinoma (PDAC). To establish reference regimens to which novel treatments can be compared in future studies, we evaluated neoadjuvant mFOLFIRINOX with or without RT in BR PDAC in a phase II National Clinical Trials Network (NCTN) trial. Methods: Pts with ECOG PS 0-1 and BR PDAC confirmed by central real-time radiographic review after pre-registration were randomized to either arm A: 8 cycles of neoadjuvant mFOLFIRINOX (oxaliplatin 85 mg/m2, irinotecan 180 mg/m2, leucovorin 400 mg/m2 and infusional 5-fluorouracil 2400 mg/m2 over 46 hours), or arm B: 7 cycles of mFOLFIRINOX followed by stereotactic body RT (SBRT, 33-40 Gy in 5 fractions [fx]) or hypofractionated image guided RT (HIGRT, 25 Gy in 5 fx). Pts in either arm without disease progression underwent pancreatectomy, then 4 cycles of adjuvant mFOLFOX6 (oxaliplatin 85 mg/m2, leucovorin 400 mg/m2 and infusional 5-fluorouracil 2400 mg/m2 over 46 hours). The primary endpoint, 18-mo OS rate, of each arm was compared to a historical control of 50%. Planned interim analysis mandated closure of either arm in which <11 of first 30 accrued pts underwent R0 resection. Results: 155 pts pre-registered and 126 pts were enrolled to arm A (N=70; 54 randomized, 16 following closure of arm B) or arm B (N=56; closed at interim analysis, all pts randomized prior to closure). Median age (A: 63y, B: 67y), median CA 19-9 level (A: 171 U/ml, B: 248 U/ml) and ECOG PS (A: 51% PS 0, B: 57% PS 0) of registered pts were similar between arms (p > 0.05). Treatment detailed in Table. The 18-mo OS rate based on Kaplan Meier estimates was 67.9% (95%CI: 54.6 – 78.0) in arm A and 47.3% (95%CI: 33.7 – 59.7) in arm B. Among pts who underwent pancreatectomy, 18-mo OS rate was 93.1% (95%CI: 84.3 – 100) and 78.9% (95%CI: 62.6 – 99.6) in arm A and B, respectively. With median follow-up of 27 and 31 mo, median OS was 31.0 (95%CI: 22.2 – NE) mo and 17.1 (95%CI: 12.8 – 24.4) mo in arm A and B, respectively. Conclusions: Neoadjuvant mFOLFIRINOX was associated with favorable OS relative to historical data in pts with BL PDAC in this phase II NCTN trial. mFOLFIRINOX with hypofractionated RT did not improve OS compared to historical data. mFOLFIRINOX represents a reference regimen in this setting and a backbone on which to add novel agents. Support: U10CA180821, U10CA180882, U24CA196171; https://acknowledgments.alliancefound.org Clinical trial information: NCT02839343. [Table: see text]

746 Background: Pelareorep is a proprietary formulation of live, replication-competent, naturally occurring Reovirus Type 3 Dearing strain. A randomized phase II trial of pelareorep in combination with carboplatin and paclitaxel in first-line treatment of metastatic PDAC (NCT01280058) was performed. Although pelareorep did not improve the primary endpoint of progression-free survival compared to carboplatin and paclitaxel alone, impressive durable responses were seen in the pelareorep arm in some patients (pts). Further, prior studies have noted the immunomodulatory carcinoembryonic antigen-related cell adhesion molecule (CEACAM6/CD66c) as a receptor for specific viral subtypes. We thus speculated that altered CEACAM6 levels may be predictive for pelareorep sensitivity. Methods: Pre-treatment tissue biopsies were collected prior enrolment for all 73 pts on study. Evaluable pts with transcriptomic data was available for only 31 pts. RNA was purified from FFPE tissue and gene expression analysis was performed using SensationPlus FFPE Amplification and WT labelling kit and the Human Transcriptome Array 2.0. CEACAM6 protein expression was determined by immunohistochemistry. Differential gene expression and survival analysis using were performed in R/Bioconductor. Appropriate corrections for multiplicity were performed. Results: When comparing extraordinary responders in the pelareorep treated arm to those with poor outcomes, low levels of CEACAM6 mRNA expression were associated with prolonged PFS in pelareorep-treated pts (adjusted p = 0.05). This effect was not seen in non-pelareorep treated pts. The luminal, but not the cytoplasmic immunohistochemistry score, was highly correlated with mRNA expression levels of CEACAM6, p = 0.001. Modulation of CEACAM6 in vitro and in vivo are underway. Conclusions: CEACAM6 may be a candidate biomarker of sensitivity to pelareorep and, in theory, could improve viral trafficking of this compound in tumor cells. Clinical trial information: NCT01280058 . [Table: see text]

e15168 Background: 2-8% of all colorectal cancer (CRC) cases are in younger adults (YAs), patients (pts) less than age 50. However, current understanding of CRC in YAs is inadequate, especially that of sporadic onset. We conducted a study to describe the landscape of genomic alterations in YA CRC pts presenting to a large academic practice. Methods: Adult pts with CRC presenting to The Ohio State University Comprehensive Cancer Center oncology clinics were offered next generation sequencing (NGS) through a customized 22-gene Ion AmpliSeq Mutation Panel as part of clinical care. Commonly mutated areas of select genes (including AKT1, ALK, BRAF, EGFR, ERBB2/4, FBXW7, FGFR1/2/3, KRAS/NRAS, MET, NOTCH1, PIK3CA, PTEN, TP53) were sequenced from tumor sections. Institutional review board approval was obtained to retrospectively analyze this NGS testing between 1/2013-3/2016. Results: 258 CRC pts underwent genomic profiling. 57 pts (22.1%) were YAs at diagnosis (range 22-49 years); 20 pts (7.8%) were 40 years old or younger. 31 YA pts (54.4%) had metastatic disease. Of the YAs with CRC, 18 pts (31.6%) were diagnosed with R-sided colon, 16 pts (28.1%) with L-sided colon, and 22 pts (38.6%) with rectal cancer. 110 genomic alterations were found in YA pts, with a mean of 1.9 mutations per tumor (range 0-6); 35 (31.8%) of these in 32 (56.1%) YA pts were actionable. Of these 110 alterations, 41.8% were in TP53, 28.2% in KRAS/NRAS, 10.0% in PIK3CA, 3.6% in BRAF, 3.6% in FBXW7, and 2.73% in PTEN. 6 YA pts (10.5%) had microsatellite instability (MSI-H). Only 1 pt had concomitant MSI-H and a BRAF mutation; 4 pts with BRAF mutations were microsatellite stable. Comparing our YA pts to a separate cohort of pts age > 50 who had testing done, no significant difference was seen in mutation incidence in KRAS/NRAS (p = 1.0), TP53 (p = 0.3), PIK3CA (p = 0.128), or BRAF (p = 1.0). Conclusions: Genomic profiling through a targeted NGS panel is feasible as part of routine clinical practice. There is disagreement in the literature on genetic mutations in YA compared to older age CRC pts. Knowledge of the genomic landscape in YAs with CRC will lead to improved understanding of the underlying biology of CRC in YAs as it differs from CRC in older pts, and could impact future care of this cohort.