PURPOSE: In patients with resectable gastric/gastroesophageal junction (GEJ) adenocarcinoma, surgery plus perioperative platinum-based chemotherapy is the standard of care. Perioperative chemotherapy remains debatable for gastric/GEJ adenocarcinoma with deficient mismatch repair (dMMR)/microsatellite instability–high (MSI-H). PATIENTS AND METHODS: NEONIPIGA (ClinicalTrials.gov identifier: NCT04006262 ) phase II study evaluated neoadjuvant nivolumab 240 mg once every two weeks ×6 and ipilimumab 1 mg/kg once every six weeks ×2, followed by surgery and adjuvant nivolumab 480 mg once every four weeks (nine injections) in patients with locally advanced resectable dMMR/MSI-H, clinical (c) tumor (T)2-T4 node (N)x metastasis (M)0 gastric/GEJ adenocarcinoma. The primary end point was a pathological complete response (pCR) rate. RESULTS: Between October 2019 and June 2021, 32 patients with dMMR/MSI-H gastric/GEJ adenocarcinoma were enrolled. The median age was 65.5 years (range, 40-80). Clinical stages were cT2-T3N0 (n = 9), cT2-T3N1 (n = 22), and cT3N1M1 (n = 1, wrongly included). With a median follow-up of 14.9 months (95% CI, 10.6 to 17.6), 32 patients received neoadjuvant immunotherapy (27 patients completed all cycles). Neoadjuvant therapy-related grade 3/4 adverse events occurred in six patients (19%). Twenty-nine patients underwent surgery; three did not have surgery and had complete endoscopic response with tumor-free biopsies and a normal computed tomography scan (two refused surgery and one had metastasis at inclusion). The rate of surgical morbidity (Clavien-Dindo classification) was 55% (one postoperative death occurred). All 29 patients had an R0 resection, and 17 (58.6%; 90% CI, 41.8 to 74.1) had pCR (pathological T0N0). Becker tumor regression grades 1a, 1b, 2, and 3 were observed in 17 patients, three (including two pathological T0N1), two, and seven patients, respectively. Of the 29 patients with surgery, 23 received adjuvant nivolumab. At database lock, no patient had relapse and one died without relapse. CONCLUSION: Nivolumab and ipilimumab-based neoadjuvant therapy is feasible and associated with no unexpected toxicity and a high pCR rate in patients with dMMR/MSI-H resectable gastric/GEJ adenocarcinoma.

Colorectal cancers with microsatellite instability (MSI) represent 15% of all colorectal cancers, including Lynch syndrome as the most frequent hereditary form of this disease. Notably, MSI colorectal cancers have a higher density of tumor-infiltrating lymphocytes (TIL) than other colorectal cancers. This feature is thought to reflect the accumulation of frameshift mutations in sequences that are repeated within gene coding regions, thereby leading to the synthesis of neoantigens recognized by CD8+ T cells. However, there has yet to be a clear link established between CD8+ TIL density and frameshift mutations in colorectal cancer. In this study, we examined this link in 103 MSI colorectal cancers from two independent cohorts where frameshift mutations in 19 genes were analyzed and CD3+, CD8+, and FOXP3+ TIL densities were quantitated. We found that CD8+ TIL density correlated positively with the total number of frameshift mutations. TIL densities increased when frameshift mutations were present within the ASTE1, HNF1A, or TCF7L2 genes, increasing even further when at least one of these frameshift mutations was present in all tumor cells. Through in vitro assays using engineered antigen-presenting cells, we were able to stimulate peripheral cytotoxic T cells obtained from colorectal cancer patients with peptides derived from frameshift mutations found in their tumors. Taken together, our results highlight the importance of a CD8+ T cell immune response against MSI colorectal cancer–specific neoantigens, establishing a preclinical rationale to target them as a personalized cellular immunotherapy strategy, an especially appealing goal for patients with Lynch syndrome. Cancer Res; 75(17); 3446–55. ©2015 AACR.

In the phase III HIMALAYA study (NCT03298451), STRIDE (Single Tremelimumab Regular Interval Durvalumab) significantly improved overall survival (OS) vs. sorafenib in unresectable HCC and demonstrated long-term survival benefits. We report an updated exploratory analysis of OS after 5 years of follow-up, including survival by multiple tumour response measures. Participants were randomised to STRIDE (tremelimumab plus durvalumab), durvalumab or sorafenib. OS, depth of response and serious adverse events were assessed. Extended long-term survivors (≥48 months beyond randomisation) were described. The updated data cut-off was 01 March 2024. Median (95% CI) follow-up durations were 62.49 (59.47-64.79) months (STRIDE) and 59.86 (58.32-61.54) months (sorafenib). The OS hazard ratio (95% CI) for STRIDE vs. sorafenib was 0.76 (0.65-0.89). OS rates at 60 months for STRIDE vs. sorafenib were 19.6% vs. 9.4% overall, 28.7% vs. 12.7% in participants achieving disease control per RECIST v1.1, and 50.7% vs. 26.3% in participants achieving >25% tumour shrinkage. No late-onset treatment-related serious adverse events were reported for STRIDE. There were more extended long-term survivors with STRIDE (83/393, 21.1%) than sorafenib (45/389, 11.6%), and extended long-term survival occurred across all clinically relevant subgroups. At 5 years, STRIDE sustained an OS benefit vs. sorafenib and maintained a manageable safety profile. OS benefit with STRIDE was improved in participants with disease control. Data suggest that any degree of tumour shrinkage with STRIDE can be associated with improved OS, indicating that conventional response measures may not fully capture the benefits of STRIDE. Nevertheless, participants experiencing deep responses appear to have the greatest benefit. STRIDE continues to set new benchmarks in unresectable HCC with 1 in 5 patients alive at 5 years. NCT03298451. The phase III HIMALAYA study showed that STRIDE (Single Tremelimumab Regular Interval Durvalumab) improved overall survival (OS) vs. sorafenib in participants with unresectable HCC, including after 4 years of follow-up. Understanding the efficacy and safety of STRIDE over the longer term is important for healthcare providers; here, we demonstrate that STRIDE sustained an OS benefit vs. sorafenib and maintained a manageable safety profile after 5 years of follow-up. OS benefit with STRIDE was improved in participants with disease control and any degree of tumour shrinkage, indicating that conventional response measures may not fully capture the benefits of STRIDE. These findings are important as they set new benchmarks in unresectable HCC and may help guide clinical decisions in the future.

Tumor DNA mismatch repair (MMR) deficiency testing is important to the identification of Lynch syndrome and decision making regarding adjuvant chemotherapy in stage II colorectal cancer (CRC) and has become an indispensable test in metastatic tumors due to the high efficacy of immune checkpoint inhibitor (ICI) in deficient MMR (dMMR) tumors. CRCs greatly benefit from this testing as approximately 15% of them are dMMR but only 3% to 5% are at a metastatic stage. MMR status can be determined by two different methods, microsatellite instability (MSI) testing on tumor DNA, and immunohistochemistry of the MMR proteins on tumor tissue. Recent studies have reported a rate of 3% to 10% of discordance between these two tests. Moreover, some reports suggest possible intra- and inter-tumoral heterogeneity of MMR and MSI status. These issues are important to know and to clarify in order to define therapeutic strategy in CRC. This review aims to detail the standard techniques used for the determination of MMR and MSI status, along with their advantages and limits. We review the discordances that may arise between these two tests, tumor heterogeneity of MMR and MSI status, and possible explanations. We also discuss the strategies designed to distinguish sporadic versus germline dMMR/MSI CRC. Finally, we present new and accurate methods aimed at determining MMR/MSI status.