Citations

TPS4175 Background: Platinum/fluoropyrimidine (FP) with PD-1 inhibitor is now established as the standard first-line therapy for most patients with advanced HER2 negative gastric, esophageal, and gastroesophageal junction (GEJ) adenocarcinoma. The FP doublet chemotherapy backbone, most commonly FOLFOX, is recommended based on marginal survival benefits of taxane-containing triplet therapy at the cost of increased toxicity. Although several agents are approved as standard treatment options in later lines, only about 10% of patients in the US receive a third line of therapy, and very few have the opportunity to benefit from all approved agents in this disease. This challenge will only increase as more agents and targeted therapies are approved. FOLFIRINOX is a triplet regimen commonly used in gastrointestinal malignancies with established safety and often with superior efficacy. Two single arm phase II trials of FOLFIRINOX have reported promising activity in GEA with manageable toxicities. Reported median overall survival (OS) from these trials is around 15 months, which is superior to what is expected from FP doublet first-line chemotherapy (about 11 months). We hypothesize that using upfront triplet therapy with a more effective and less toxic triplet combination will result in improved patient outcomes by optimization of available therapies in GEA. Methods: This study is a randomized phase III, open-label, multicenter clinical trial with the primary objective to determine whether modified FOLFIRINOX (FU 2400 mg/m2, leucovorin 400 mg/m2, oxaliplatin 85 mg/m2, irinotecan 150 mg/m2 every 2 weeks) as first-line treatment improves OS compared to mFOLFOX in patients with advanced HER2 negative GEA. Eligible patients will have unresectable or metastatic adenocarcinoma of esophagus, GEJ, or stomach with no prior systemic treatment. Patients must have adequate organ function, and measurable or evaluable disease as defined by RECIST 1.1. Prior neoadjuvant or adjuvant therapy is allowed if completed at least 1 year prior to registration. Patients who will receive nivolumab (mandatory for PD-L1 combined positive score > 5) in addition to chemotherapy must not have any contraindications to immune checkpoint inhibitors. Patients with treated, asymptomatic and stable brain metastases are eligible. The total sample size is 382 evaluable patients for this study (191 patients per arm). The study accrual began January 2023. Clinical trial information: NCT05677490 .

4146 Background: Currently, ICI therapy is recommended for patients with metastatic PDAC whose tumors exhibit dMMR, MSI-H, or high TMB (≥10 mutations/Mb). However, due to the low prevalence of high TMB in PDAC (~1%), few studies have evaluated the role of ICI therapy in this subpopulation. This study aimed to compare GA between PDAC patients with high TMB and low TMB ( < 10 mutations/Mb) and to evaluate the effectiveness of ICIs in real-world PDAC patients by TMB status. Methods: This study included PDAC patients who underwent genomic testing using Foundation Medicine tissue comprehensive genomic profiling (CGP) assays. GA were compared between tissue specimens with high and low TMB by chi-squared, adjusted for multiple comparisons. Patient clinical data was obtained by the US-wide de-identified Flatiron Health and Foundation Medicine real-world clinicogenomic pancreatic database (CGDB), originated from ~280 US cancer clinics between 01/2011 and 09/2022. Real-world overall survival (OS) and time to treatment discontinuation (TTD) were compared between patients receiving an ICI (high TMB versus low TMB) and between patients with high TMB (ICI versus other therapies) by Cox models. Results: We included 21,932 patients with PDAC with tissue CGP data available; 98.7% with low TMB and 1.3% with high TMB. Among actionable alterations, patients with high TMB had higher prevalence of mutations in BRCA2 (p < 0.0001), BRAF (p < 0.0001), PALB2 (p < 0.0001), and genes of the mismatch repair pathway ( MSH2, MSH6, MLH1, and PMS2, p < 0.0001), but lower prevalence of KRAS mutations (p < 0.0001). The most common KRAS mutation in both groups of patients was G12D. In CGDB, 51 patients received an ICI (10 with high TMB and 41 with low TMB) and 17 patients with high TMB received other therapies. Among patients receiving an ICI, those with high TMB had more favorable median OS compared to those with low TMB (25.7 versus 5.2 months, hazard ratio (HR) 0.27, 95% confidence interval (CI) 0.09 - 0.76, p = 0.01) and median TTD (20.7 versus 3.0 months, HR 0.33, 95% CI 0.13 - 0.82, p = 0.02). Among patients with high TMB, those receiving an ICI had more favorable OS compared to those receiving other therapies (25.7 versus 6.6 months, HR 0.31, 95% CI 0.10-0.96, p = 0.043), nominally favoring ICI use in this small cohort (n = 10 versus 17). Conclusions: There is no randomized clinical trial evaluating ICI versus other therapies in PDAC. To our knowledge, this is the largest cohort to date comparing ICI effectiveness in PDAC. We observed more favorable OS among PDAC patients with high TMB receiving ICI versus those with low TMB who received an ICI and more favorable to those with high TMB receiving other therapies. This study supports the FDA-approved use of ICIs in patients with PDAC and high TMB and demonstrates the importance of TMB assessment for patients with PDAC.

4084 Background: Treatment of advanced CCA has changed dramatically over the past five years with the advent of molecularly targeted therapy, now approved in the 2nd line and beyond. However, real world utilization of molecular profiling and targeted therapy is still unknown and these data are critical to empower treatment decision-making. Methods: In 2019, the Cholangiocarcinoma Foundation (CCF) and Ciitizen (a wholly owned subsidiary of Invitae Corporation) collaboratively launched a registry platform that directly consents patients and collects comprehensive medical records. De-identified data including clinical characteristics, molecular testing, interventions, and outcomes are extracted and standardized for research use. The data is longitudinal with regularly planned updates; registry participants can be re-engaged to obtain additional data and communicate tailored insights. Results: We quantified the rate of molecular testing, the presence of targetable biomarkers, and the utilization and outcomes on matched targeted therapies for 372 individuals with CCA. 328 (88.2%) individuals had molecular testing, with the identified targetable mutations and matched therapies reported. Of 328 individuals who had molecular testing, 111 (33.8%) individuals had one or more targetable mutations (116 mutations total). Only 46% (51) of individuals with targetable mutations received targeted therapy. Of the 54% (60) individuals with targetable mutations that did not receive any matched therapy, the majority (61.7%, 37) were in early disease or first line of treatment and therefore not yet eligible for targeted therapy. These individuals will be informed that based on their molecular profile, a targeted therapy may be an option, and suggest they discuss with their treating physician. Conclusions: A novel prospectively-maintained database registry for CCA has been formed in collaboration between a patient advocacy organization (CCF) and industry (Invitae). Prevalence of actionable biomarkers was higher than historically expected and may reflect patient utilization bias of the registry platform. Molecular profiling and access to targeted therapeutics remains suboptimal at this time in CCA. Future directions for the registry include identifying and targeting disparities in care and supporting biopharmaceutical development and regulatory decisions. [Table: see text]

4028 Background: T-cell immunoreceptor with immunoglobulin and immunoreceptor tyrosine-based inhibitory motif domains (TIGIT) inhibitor in combination with an anti-programmed cell death protein 1 (PD-1) antibody has shown antitumor activity in solid tumors. AdvanTIG-105 (NCT04047862) is a phase 1/1b open-label study designed to assess the safety and preliminary antitumor activity of OCI, an anti-TIGIT monoclonal antibody (mAb), + TIS, an anti-PD-1 mAb, in pts with unresectable, locally advanced or metastatic solid tumors. In the dose-escalation part, OCI + TIS was well tolerated with preliminary antitumor activity observed, and the recommended phase 2 dose (RP2D) of OCI 900 mg intravenously (IV) every three weeks (Q3W) + TIS 200 mg IV Q3W was established. We report results from the dose-expansion part (GC/GEJC Cohort 9) of the AdvanTIG-105 study. Methods: Eligible pts had histologically/cytologically confirmed stage IV GC/GEJC. Pts were excluded if they had squamous cell, undifferentiated or other histological types of GC, had GC/GEJC with positive HER2 expression, or if they had received any prior therapy for metastatic disease. Pts received either the RP2D of OCI + TIS with oxaliplatin + capecitabine Q3W for 6 cycles (C), followed by maintenance therapy with the RP2D of OCI + TIS, + capecitabine Q3W, or the RP2D of OCI + TIS with cisplatin + 5-fluorouracil Q3W for 6 C. Treatment continued until disease progression, intolerable toxicity, or withdrawal of consent. The primary endpoint was investigator-assessed overall response rate (ORR) per RECIST v1.1. Secondary endpoints included progression-free survival (PFS), duration of response (DoR), disease control rate (DCR) per RECIST v1.1, and safety. Results: As of September 29, 2022, 60 pts with a median age of 61.5 years (range 35-82) were enrolled; 59 were efficacy evaluable. Median study follow-up was 31.1 weeks (range 1.4-78.4). ORR was 50.8% (95% CI: 37.5, 64.1); DCR was 84.7% (95% CI: 73.0, 92.8) with a median DoR of 8.1 months (95% CI: 4.5, not evaluable [NE]). Median PFS was 8.2 months (95% CI: 5.8, NE). In a subgroup analysis, ORR in pts with PD-L1 tumor area positivity (TAP) score ≥5% (n = 27) was 59.3% (95% CI: 38.8, 77.6), and 50.0% (95% CI: 30.7, 69.4) in pts with PD-L1 TAP < 5% (n = 28). All 60 pts reported ≥1 treatment-emergent adverse event (TEAE), the most common being anemia (43.3%) and platelet count decreased (41.7%). In total, 43 pts (71.7%) had ≥grade 3 TEAEs and 28 (46.7%) had serious adverse events. TEAEs leading to discontinuation of TIS and OCI occurred in 5 (8.3%) pts. TEAEs led to death in 2 (3.3%) pts; one event (neutropenic sepsis) was related to chemo, while the other (pulmonary embolism) was not treatment related. Conclusions: OCI 900 mg + TIS 200 mg + chemo was generally well tolerated and showed encouraging antitumor activity in pts with stage IV GC/GEJC. Clinical trial information: NCT04047862 .

4027 Background: DKN-01 is an anti-DKK1 mAb which has demonstrated anti-tumor activity in patients with advanced GEA with low tumor PD-L1 expression, a subset with very limited therapeutic options. DKN-01 has immunomodulatory activity, stimulates a pro-inflammatory tumor microenvironment, and upregulates PD-L1 levels. Here we present 2-year survival data for 1L advanced GEA patients who received combination treatment with DKN-01, the Fc-optimized anti-PD-1 tislelizumab, and CAPOX chemotherapy. The ORR was previously reported (68% in ITT and 79% in PD-L1-low populations). Methods: This Phase 2, multi-center, single arm Part A of the DisTinGuish (NCT04363801) study investigated DKN-01 + tislelizumab + CAPOX as 1L therapy in advanced HER2(-) GEA, regardless of DKK1 and PD-L1 expression levels. Tumor DKK1 and PD-L1 were assessed by central laboratories. The primary endpoint was ORR in a modified intent to treat population (>1 dose DKN-01); secondary endpoints included PFS and OS in the ITT population. Results: Twenty-five patients were enrolled from September 2020 to April 2021. As of 23 January 2023: Median age was 61 years (22, 80); 17 patients had GEJ adenocarcinoma; 8 had gastric cancer. Twenty-one patients had tumors with evaluable DKK1 expression. Twenty-two patients had tumors with evaluable PD-L1 expression; the majority (73%) were low expressors (vCPS <5%). Median (m) duration on treatment is 11.3 months (mo). Seven patients remain on study, with 4 on-treatment beyond 2 years. The mPFS is 11.3 mo in the overall ITT population and 10.7 mo in patients with low tumor PD-L1 expression. The mOS is 19.5 mo in the overall ITT population and 18.7 mo in the patients with low tumor PD-L1 expression. Treatment related adverse events (TRAEs) were mild with most G1/2. The most common AEs related to the study drug regimen were nausea (72%), diarrhea (64%) and fatigue (60%). Five patients experienced G3 DKN-01-TRAEs including decreased neutrophil count (1), diarrhea (1), vomiting (1), hypophosphatemia (2), and pulmonary embolism (1). Conclusions: At 2-years of follow-up, 1L treatment of advanced GEA patients with DKN-01 in combination with tislelizumab and CAPOX resulted in a prolongation of PFS and OS compared with the modern SOC regimen of nivolumab plus chemotherapy, both in the overall population (mPFS 11.3 vs 7.7 mo; mOS 19.5 vs 13.8 mo) and in the PD-L1 low subgroup (mPFS 10.7 vs 7.5 mo; mOS 18.7 vs 12.4 mo), alongside a manageable safety profile. The prolonged PFS and OS observed in the current study are notable, especially in our trial population dominated by patients with tumors of low PD-L1 expression, where the known benefit of anti-PD-1 therapy is limited. The ongoing Part C of this study is evaluating mFOLFOX6/CAPOX plus tislelizumab with or without DKN-01 in the same 1L GEA patient population. Further evaluation of biomarkers is also ongoing. Clinical trial information: NCT04363801 .

4007 Background: Biliary tract cancer (BTC) is an aggressive malignancy with a poor prognosis, and current treatment options for advanced BTC are limited, with second-line therapy, FOLFOX and S-1 offering an objective response rate (ORR) of 5.0% and 7.5%, respectively. Up to 20% of BTCs overexpress human epidermal growth factor receptor 2 (HER2). Tucatinib (TUC) is a highly selective HER2-directed TKI approved for HER2-positive (HER2+) metastatic breast and colorectal cancer. Discussed here are the efficacy and safety results of TUC combined with Trastuzumab (Tras) in pts with previously treated HER2+ metastatic BTC. Methods: SGNTUC-019 (NCT04579380) is an open-label phase 2 basket study evaluating efficacy, safety, and tolerability of TUC and Tras in pts with HER2-altered solid tumors. Pts in the BTC cohort had been previously treated with and progressed after ≥1 line of systemic therapy for metastatic disease. Eligible pts had locally determined HER2+ (defined as HER2 overexpression determined by immunohistochemistry [IHC] 3+ or HER2 amplification determined by in situ hybridization assay or next-generation sequencing) metastatic BTC. Pts were treated on a 21-day cycle with TUC (300 mg orally twice a day) and Tras (8 mg/kg IV followed by 6 mg/kg every 3 wks). Disease status was determined based on RECIST v1.1 with assessments performed every 6 wks for 24 wks and every 12 wks thereafter. The primary endpoint is confirmed objective response rate (cORR) per investigator assessment. Secondary endpoints include overall survival (OS), disease control rate (DCR), duration of response (DOR), progression-free survival (PFS), and safety. Results: Thirty pts were enrolled in the BTC cohort as of data cutoff date of 30 Nov 2022. The median duration of follow-up was 8.3 months. cORR was 46.7% (90% CI, 30.8, 63.0), with 14 responses including 1 complete and 13 partial responses. Median DOR was 6.0 months (90% CI, 5.5, not estimable). DCR was 76.7% (n=23; 90% CI, 60.6, 88.5), and median PFS was 5.5 months (90% CI, 3.9, 8.1). At data cutoff, 13 (43.3%) patients had died, and the 12-months OS rate was 53.8% (90% CI, 35.2, 69.1%). Overall, the most common treatment-emergent adverse events (TEAEs) reported were pyrexia (43.3%) and diarrhea (40.0%). Grade ≥3 TEAEs were reported in 18 (60.0%) of 30 pts; however, only 6 (20.0%) and 2 (6.7%) of these pts had Grade ≥3 TEAEs related to TUC and Tras, respectively. Two (6.7%) pts discontinued TUC due to TEAEs, cholangitis and liver disorder. No deaths were due to TEAEs. Conclusions: The combination of TUC and Tras was well tolerated in pts with previously treated HER2+ metastatic BTC. The observed antitumor activity supports the combination of TUC and Tras as a future chemotherapy-free treatment option for this population with historically poor outcomes. Clinical trial information: NCT04579380 .

4006 Background: Liposomal irinotecan + 5-fluorouracil/leucovorin (5-FU/LV) is approved in the USA and Europe for mPDAC following progression with gemcitabine-based therapy. A phase 1/2 study (NCT02551991) demonstrated promising anti-tumor activity in patients with mPDAC who received first-line liposomal irinotecan 50 mg/m2 + 5-FU 2400 mg/m2 + LV 400 mg/m2 + oxaliplatin 60 mg/m2 (NALIRIFOX). Here, we present results from NAPOLI 3 (NCT04083235), a randomized, open-label, phase 3 study investigating the efficacy and safety of NALIRIFOX compared with nab-paclitaxel 125 mg/m2 + gemcitabine 1000 mg/m2 (Gem+NabP) as first-line therapy in patients with mPDAC. Methods: Eligible patients with histopathologically/cytologically confirmed untreated mPDAC were randomized (1:1; stratified by Eastern Cooperative Oncology Group [ECOG] performance status, geographic region and presence/absence of liver metastases) to receive NALIRIFOX on days 1 and 15 of a 28-day cycle or Gem+NabP on days 1, 8 and 15 of a 28-day cycle. The primary endpoint was overall survival (OS); secondary endpoints were progression-free survival (PFS), overall response rate (ORR) and safety. OS was evaluated when at least 543 events were observed using a stratified log-rank test with an overall one-sided significance level of 0.025. Results: Overall, 770 patients (NALIRIFOX, n = 383; Gem+NabP, n = 387) were included. Baseline characteristics were balanced between arms. At a median follow-up of 16.1 months, 544 events had occurred. Median OS was 11.1 months in the NALIRIFOX group versus 9.2 months in the Gem+NabP group; median PFS was 7.4 months versus 5.6 months. Median (95% CI) duration of response was 7.3 (5.8–7.6) and 5.0 (3.8–5.6) months in patients who received NALIRIFOX and Gem+NabP, respectively. Grade 3/4 treatment-emergent adverse events occurring in at least 10% of patients receiving NALIRIFOX versus Gem+NabP included diarrhea (20.3% vs 4.5%), nausea (11.9% vs 2.6%), hypokalemia (15.1% vs 4.0%), anemia (10.5% vs 17.4%) and neutropenia (14.1% vs 24.5%). Conclusions: First-line NALIRIFOX demonstrated clinically meaningful and statistically significant improvement in OS and PFS compared with Gem+NabP in patients with mPDAC. The NALIRIFOX safety profile was consistent with the profiles of the regimen components and generally manageable. Clinical trial information: NCT04083235 . [Table: see text]

4004 Background: Immune checkpoint inhibitor (ICI) studies have shown an association between the occurrence of imAEs and outcomes. In the Phase 3 HIMALAYA study (NCT03298451) in uHCC, STRIDE (Single T Regular Interval D) significantly improved overall survival (OS) vs sorafenib (S), and D monotherapy was noninferior to S. STRIDE and D had manageable safety (Abou-Alfa et al. NEJM Evid 2022). STRIDE is approved for uHCC in the United States and Japan and recommended for approval by the European Medicines Agency; D is approved in Japan. This exploratory analysis assessed the association between imAEs and outcomes in HIMALAYA. Methods: Safety was assessed in participants (pts) who received ≥1 dose of STRIDE (T 300 mg [one dose] plus D 1500 mg once every 4 weeks [Q4W]) or D (1500 mg Q4W). imAEs were AEs of special interest associated with drug exposure and consistent with an immune-mediated mechanism of action with no found alternate etiology. Median OS (mOS) and OS rates were estimated using the Kaplan–Meier method. OS hazard ratios (HRs) and 95% CIs were calculated using Cox modeling, with imAEs as a time-varying covariate and stratified by etiology (HBV/HCV/others), ECOG (0/1), and macro-vascular invasion (yes/no) for pts with vs without imAEs of any grade. Pts with >1 imAE were counted once. Results: In total, 388 pts (STRIDE) and 388 pts (D) were included in the analysis. Any grade imAEs, Grade 3 or 4 imAEs, and imAEs leading to discontinuation occurred in 139 (35.8%), 49 (12.6%), and 22 (5.7%) pts, respectively for STRIDE and 64 (16.5%), 25 (6.4%), and 10 (2.6%) pts, respectively for D. imAEs requiring high-dose steroids (≥40 mg prednisone or equivalent daily) occurred in 78 (20.1%) pts for STRIDE and 37 (9.5%) pts for D. An improvement in OS was seen with STRIDE in pts with imAEs vs pts without (HR, 0.73; 95% CI, 0.56–0.95). OS rates at 6, 12, and 24 months (mo) were higher for STRIDE in pts with imAEs vs pts without. The association between imAEs and OS was less clear for D and may be limited by small pt number. In a landmark analysis of pts with vs without imAEs within 6 mo of STRIDE (n=307) or D (n=287), OS HRs (95% CIs) were 0.65 (0.47–0.90) and 1.39 (0.95–2.04), respectively. Conclusions: In HIMALAYA, imAEs with STRIDE or D were manageable and generally low grade. In this exploratory analysis, the occurrence of imAEs was associated with improved OS for STRIDE, generally consistent with findings for other ICIs. Clinical trial information: NCT03298451 . [Table: see text]

e15640 Background: The standard management of locally advanced rectal cancer (LARC) is neo-adjuvant concurrent chemo radiation (CCRT) followed by total meso-rectal excision. Recently there is an increased interest in total neo-adjuvant treatment (TNT). Most patients with rectal cancer in developing countries present in advanced stage for several reasons including lack of resources and delayed health seeking behavior. Most patients are not able to get standard management. This study tries to assess treatment patterns and outcomes in LARC. Methods: A cross-sectional study was conducted in patients with LARC that are treated at TASH from Jan 1, 2020 up to Sept. 2022. The data was collected from Patient’s cards using a pre-structured format that included demographic data, laboratory, pathological and imaging information. Data analysis was conducted by using IBM SPSS version 25. Results: 100 patients were included in the study, 51% were male. The median (range) age at diagnosis was 45.5 (20-86) years. 81% of patients came to our center without getting any oncologic treatment and 75.3% of them were presented on a multi-disciplinary tumor board for their treatment decision. Upfront surgery was decided in 48.1% (39/81) of patients. Standard neo-adjuvant treatment of either TNT or CCRT was decided in 23.4% (19/81) and 8.6% (7/81) of patients respectively. There is no significant association between tumor location, TNM stage, mesorectal fascia status and first treatment decision. Only 12 (14.8%) patients were able to finish their whole treatment plan. The most common reason for not finishing all treatment was prolonged radiation waiting time, with the median (range) waiting time of 10 ± 7.1 (1-26) months. From 81 treatment naive patients, 79 were decided to have surgery; and 59.5% (47/79) underwent the planned surgery with 89.9% R0 resection rate. R0 resection rate in patients who undergo upfront surgery was 91.2% (31/34). Neo-adjuvant chemotherapy was given to 34.6% (28/81); and only 18% (5/28) underwent subsequent surgery. The most common reason for not undergoing subsequent surgery was disease progression 43.5% (10/23) during or after finishing the neo-adjuvant chemotherapy. Only 24% of the study participants received radiotherapy. From the patients who took radiotherapy, only two patients received short course radiotherapy. Conclusions: Treatment decisions for rectal cancer in our study did not conform to standard treatment recommendations. Upfront surgery maybe a better option than neoadjuvant chemotherapy, since timely administration of standard neoadjuvant treatment is not possible. Alternative radiotherapy treatment options like short course radiotherapy may be better in resource limited setting to alleviate the longer radiotherapy waiting time.

e15626 Background: Studies have shown the effectiveness of immune checkpoint inhibition (ICI) in patients with tumors demonstrating microsatellite instability (MSI-H) and an associated defect in DNA mismatch repair (dMMR). In particular, KEYNOTE-177 demonstrated significant survival benefit for patients with unresectable or metastatic colorectal cancer with MSI-H or dMMR. Recently published case reports and series have demonstrated similar outcomes for patients with locally advanced and resectable rectal cancer. We report on the experience of patients with locally advanced, resectable rectal adenocarcinoma treated across the Mayo Clinic Health System. Methods: We conducted a retrospective analysis of patients treated at Mayo Clinic since 2015 A search of the Mayo Clinic database was done to include parameters for confirmed rectal adenocarcinoma, dMMR in pathology reports. Patients receiving ICI treatment including pembrolizumab, nivolumab/ipilimumab and durvalumab in any combination with chemotherapy and/or radiation were included. Patients with metastatic disease at the time of surgical intervention or ICI were excluded. Clinical data was assimilated. Results: Twenty-one patients met criteria for inclusion in our analysis. Fifteen patients had de novo disease. Six patients had local recurrence and had been treated previously with chemotherapy, radiation (RT) and surgery. None of the patients included had prior ICI therapy. Fifteen patients had Lynch syndrome. The median age of diagnosis was 41.5 years. Seven patients underwent surgical intervention. of the seven patients received surgery upfront followed by immunotherapy. The remaining six had neoadjuvant immunotherapy alone or in combination with chemotherapy and/or radiation. Prior to surgery, all patients demonstrated radiographic partial response (rPR). 67% of these demonstrated a pathologic complete response (pCR) while 33% had residual disease. The patient who received surgery upfront and adjuvant ICI continues to have radiographic stable disease after 1 year of treatment. For patients who did not have surgery, 50% had radiographic “complete or near complete” response (rCR), 43% had rPR and 7% had radiographic stable disease. Ten patients received RT and ICI with 70% demonstrating rCR and 30% rPR. Overall, the objective response rate was 90 Response to treatment was observed upwards of 75 months. Only 1 person in the study had progression of disease that occurred after 14 months of therapy. Conclusions: Similar to KEYNOTE-177, patients with locally advanced MSI-H/dMMR rectal cancer have significant and durable response to immunotherapy alone or in combination with chemotherapy, radiation and surgery. Further large prospective trials are needed to validate these findings and determine a standardized approach.