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PD-1 plus CTLA-4 blockade is highly effective in advanced-stage, mismatch repair (MMR)-deficient (dMMR) colorectal cancers, yet not in MMR-proficient (pMMR) tumors. We postulated a higher efficacy of neoadjuvant immunotherapy in early-stage colon cancers. In the exploratory NICHE study (ClinicalTrials.gov: NCT03026140 ), patients with dMMR or pMMR tumors received a single dose of ipilimumab and two doses of nivolumab before surgery, the pMMR group with or without celecoxib. The primary objective was safety and feasibility; 40 patients with 21 dMMR and 20 pMMR tumors were treated, and 3 patients received nivolumab monotherapy in the safety run-in. Treatment was well tolerated and all patients underwent radical resections without delays, meeting the primary endpoint. Of the patients who received ipilimumab + nivolumab (20 dMMR and 15 pMMR tumors), 35 were evaluable for efficacy and translational endpoints. Pathological response was observed in 20/20 (100%; 95% exact confidence interval (CI): 86–100%) dMMR tumors, with 19 major pathological responses (MPRs, ≤10% residual viable tumor) and 12 pathological complete responses. In pMMR tumors, 4/15 (27%; 95% exact CI: 8–55%) showed pathological responses, with 3 MPRs and 1 partial response. CD8 + PD-1 + T cell infiltration was predictive of response in pMMR tumors. These data indicate that neoadjuvant immunotherapy may have the potential to become the standard of care for a defined group of colon cancer patients when validated in larger studies with at least 3 years of disease-free survival data. Results from the NICHE study show remarkable pathological responses to neoadjuvant combination immunotherapy in patients with early-stage colon cancer and uncover potential biomarkers of response.

Pembrolizumab has shown improved progression-free survival versus chemotherapy in patients with newly diagnosed microsatellite instability-high or mismatch repair-deficient metastatic colorectal cancer. However, the treatment's effect on overall survival in this cohort of patients was unknown. Here, we present the final overall survival analysis of the KEYNOTE-177 study. This randomised, open-label, phase 3 study was done in 193 academic medical centres and hospitals in 23 countries. We recruited patients aged at least 18 years, with an Eastern Cooperative Oncology Group performance status of 0 or 1, and who had previously untreated microsatellite instability-high or mismatch repair-deficient metastatic colorectal cancer. Patients were randomly assigned (1:1) in blocks of four using an interactive voice response system or integrated web response system to intravenous pembrolizumab 200 mg every 3 weeks or to the investigator's choice of intravenous mFOLFOX6 (oxaliplatin 85 mg/m2 on day 1, leucovorin 400 mg/m2 on day 1, and fluorouracil 400 mg/m2 bolus on day 1 followed by a continuous infusion of 1200 mg/m2 per day for 2 days on days 1–2) or intravenous FOLFIRI (irinotecan 180 mg/m2 on day 1, leucovorin 400 mg/m2 on day 1, and fluorouracil 400 mg/m2 bolus on day 1 followed by a continuous infusion of 1200 mg/m2 per day for 2 days on days 1–2), every 2 weeks with or without intravenous bevacizumab 5 mg/kg every 2 weeks or intravenous weekly cetuximab (first dose 400 mg/m2, then 250 mg/m2 for every subsequent dose). Patients receiving chemotherapy could cross over to pembrolizumab for up to 35 treatment cycles after progression. The co-primary endpoints were overall survival and progression-free survival in the intention-to-treat population. KEYNOTE-177 is registered at ClinicalTrials.gov, NCT02563002, and is no longer enrolling patients. Between Feb 11, 2016, and Feb 19, 2018, 852 patients were screened, of whom 307 (36%) were randomly assigned to pembrolizumab (n=153) or chemotherapy (n=154). 93 (60%) patients crossed over from chemotherapy to anti-PD-1 or anti-PD-L1 therapy (56 patients to on-study pembrolizumab and 37 patients to off-study therapy). At final analysis (median follow-up of 44·5 months [IQR 39·7–49·8]), median overall survival was not reached (NR; 95% CI 49·2–NR) with pembrolizumab vs 36·7 months (27·6–NR) with chemotherapy (hazard ratio [HR] 0·74; 95% CI 0·53–1·03; p=0·036). Superiority of pembrolizumab versus chemotherapy for overall survival was not demonstrated because the prespecified α of 0·025 needed for statistical significance was not achieved. At this updated analysis, median progression-free survival was 16·5 months (95% CI 5·4–38·1) with pembrolizumab versus 8·2 months (6·1–10·2) with chemotherapy (HR 0·59, 95% CI 0·45–0·79). Treatment-related adverse events of grade 3 or worse occurred in 33 (22%) of 153 patients in the pembrolizumab group versus 95 (66%) of 143 patients in the chemotherapy group. Common adverse events of grade 3 or worse that were attributed to pembrolizumab were increased alanine aminotransferase, colitis, diarrhoea, and fatigue in three (2%) patients each, and those attributed to chemotherapy were decreased neutrophil count (in 24 [17%] patients), neutropenia (22 [15%]), diarrhoea (14 [10%]), and fatigue (13 [9%]). Serious adverse events attributed to study treatment occurred in 25 (16%) patients in the pembrolizumab group and in 41 (29%) patients in the chemotherapy group. No deaths attributed to pembrolizumab occurred; one death due to intestinal perforation was attributed to chemotherapy. In this updated analysis, although pembrolizumab continued to show durable antitumour activity and fewer treatment-related adverse events compared with chemotherapy, there was no significant difference in overall survival between the two treatment groups. These findings support pembrolizumab as an efficacious first-line therapy in patients with microsatellite instability-high or mismatch repair-deficient metastatic colorectal cancer. MSD.

Mismatch repair deficiency (dMMR) is found in approximately 15% of non-metastatic colon cancers (CCs) and is characterized by a defective DNA mismatch repair system, resulting in hypermutated and highly immunogenic tumors. Although patients with dMMR CC have limited benefit from chemotherapy, these tumors have been shown to respond exceptionally well to neoadjuvant anti-PD-1 plus anti-CTLA-4, with high rates of pathologic responses. Here, based on data from melanoma studies, we postulated a high efficacy and favorable toxicity profile of anti-PD-1 plus anti-LAG-3. In the NICHE-3 study, a total of 59 patients with locally advanced dMMR CC were treated with two 4-weekly cycles of nivolumab (480 mg) plus relatlimab (480 mg) before surgery. Pathologic response was observed in 57 of 59 (97%; 95% confidence interval (CI): 88–100%) patients, meeting the primary endpoint. Responses included 54 (92%; 95% CI: 81–97%) major pathologic responses (≤10% residual viable tumor) and 40 (68%; 95% CI: 54–79%) pathologic complete responses. With a median follow-up of 8 months (range, 2–19), one patient had recurrence of disease. The treatment displayed an acceptable safety profile, with all-grade and grade 3–4 immune-related adverse events (irAEs) occurring in 80% and 10% of patients, respectively. The most common irAEs were infusion-related reactions (29%), thyroid dysfunction (22%) and fatigue (20%). In conclusion, our results show that neoadjuvant nivolumab/relatlimab induces high rates of pathologic responses and that further investigation of this treatment in larger studies is warranted. These data add to the body of evidence in support of neoadjuvant immunotherapy regimens in dMMR CC. ClinicalTrials.gov identifier: NCT03026140 . In the phase 2 NICHE-3 trial, patients with locally advanced mismatch repair-deficient colon cancer who were treated with neoadjuvant anti-PD1 and anti-LAG3 agents showed high rates of pathological responses, requiring validation in larger trials.

IntroductionLynch syndrome (LS) and constitutional mismatch repair deficiency (CMMRD) are hereditary cancer syndromes associated with mismatch repair (MMR) deficiency. Tumours show microsatellite instability (MSI), also reported at low levels in non-neoplastic tissues. Our aim was to evaluate the performance of high-sensitivity MSI (hs-MSI) assessment for the identification of LS and CMMRD in non-neoplastic tissues.Materials and methodsBlood DNA samples from 131 individuals were grouped into three cohorts: baseline (22 controls), training (11 CMMRD, 48 LS and 15 controls) and validation (18 CMMRD and 18 controls). Custom next generation sequencing panel and bioinformatics pipeline were used to detect insertions and deletions in microsatellite markers. An hs-MSI score was calculated representing the percentage of unstable markers.ResultsThe hs-MSI score was significantly higher in CMMRD blood samples when compared with controls in the training cohort (p<0.001). This finding was confirmed in the validation set, reaching 100% specificity and sensitivity. Higher hs-MSI scores were detected in biallelic MSH2 carriers (n=5) compared with MSH6 carriers (n=15). The hs-MSI analysis did not detect a difference between LS and control blood samples (p=0.564).ConclusionsThe hs-MSI approach is a valuable tool for CMMRD diagnosis, especially in suspected patients harbouring MMR variants of unknown significance or non-detected biallelic germline mutations.

A deficient mismatch repair system (dMMR) is present in 10–20% of patients with sporadic colorectal cancer (CRC) and is associated with a favourable prognosis in early stage disease. Data on patients with advanced disease are scarce. Our aim was to investigate the incidence and outcome of sporadic dMMR in advanced CRC. Data were collected from a phase III study in 820 advanced CRC patients. Expression of mismatch repair proteins was examined by immunohistochemistry. In addition microsatellite instability analysis was performed and the methylation status of the MLH1 promoter was assessed. We then correlated MMR status to clinical outcome. Deficient mismatch repair was found in only 18 (3.5%) out of 515 evaluable patients, of which 13 were caused by hypermethylation of the MLH1 promoter. The median overall survival in proficient MMR (pMMR), dMMR caused by hypermethylation of the MLH1 promoter and total dMMR was 17.9 months (95% confidence interval 16.2–18.8), 7.4 months (95% CI 3.7–16.9) and 10.2 months (95% CI 5.9–19.8), respectively. The disease control rate in pMMR and dMMR patients was 83% (95% CI 79–86%) and 56% (30–80%), respectively. We conclude that dMMR is rare in patients with sporadic advanced CRC. This supports the hypothesis that dMMR tumours have a reduced metastatic potential, as is observed in dMMR patients with early stage disease. The low incidence of dMMR does not allow drawing meaningful conclusions about the outcome of treatment in these patients.

Deficient mismatch repair system (dMMR)/microsatellite instability (MSI) is found in about 5% of metastatic colorectal cancers (mCRCs) with a major therapeutic impact for immune checkpoint inhibitor (ICI) use. We conducted a multicentre study including all consecutive patients with a dMMR/MSI mCRC. MSI status was determined using the Pentaplex panel and expression of the four MMR proteins was evaluated by immunohistochemistry (IHC). The primary endpoint was the rate of discordance of dMMR/MSI status between primary tumours and paired metastases. We included 99 patients with a dMMR/MSI primary CRC and 117 paired metastases. Only four discrepancies (3.4%) with a dMMR/MSI primary CRC and a pMMR/MSS metastasis were initially identified and reviewed by expert pathologists and molecular biologists. Two cases were false discrepancies due to human or technical errors. One discordant case could not be confirmed due to the low level of tumour cells. The last case had a confirmed discrepancy with a dMMR/MSI primary CRC and a pMMR/MSS peritoneal metastasis. Our study demonstrated a high concordance rate of dMMR/MSI status between primary CRCs and their metastases. The analysis of one sample, either from the primary tumour or metastasis, with consistent dMMR and MSI status seems to be sufficient prior to treatment with ICI.

Community microattribution review of the evidence for colon cancer risk conferred by constitutional variants in MLH1 , MSH2 , MSH6 and PMS2 has resulted in the reclassification of two-thirds of the variants reported in existing databases and led to clinical recommendations for the interpretation of 1,370 variants that do not result in obvious protein truncation. The clinical classification of hereditary sequence variants identified in disease-related genes directly affects clinical management of patients and their relatives. The International Society for Gastrointestinal Hereditary Tumours (InSiGHT) undertook a collaborative effort to develop, test and apply a standardized classification scheme to constitutional variants in the Lynch syndrome–associated genes MLH1 , MSH2 , MSH6 and PMS2 . Unpublished data submission was encouraged to assist in variant classification and was recognized through microattribution. The scheme was refined by multidisciplinary expert committee review of the clinical and functional data available for variants, applied to 2,360 sequence alterations, and disseminated online. Assessment using validated criteria altered classifications for 66% of 12,006 database entries. Clinical recommendations based on transparent evaluation are now possible for 1,370 variants that were not obviously protein truncating from nomenclature. This large-scale endeavor will facilitate the consistent management of families suspected to have Lynch syndrome and demonstrates the value of multidisciplinary collaboration in the curation and classification of variants in public locus-specific databases.

This trial tested the influence of aspirin or resistant starch on the incidence of colorectal cancer or colonic adenomas in patients with the Lynch syndrome (hereditary nonpolyposis colon cancer). Neither intervention influenced the incidence of colorectal neoplasms in the Lynch syndrome. Neither aspirin or resistant starch influenced the incidence of colorectal neoplasms in the Lynch syndrome. The regular use of aspirin or aspirin-like agents is associated with a moderate reduction in the risk of colonic polyps and colorectal cancer. 1 – 4 Randomized trials of high-fiber diets have not shown a reduction in the risk of adenomas or colorectal cancer, 5 but none have investigated the effects of resistant starch. There is epidemiologic evidence of a negative correlation between colon cancer and starch intake. 6 Resistant starches escape digestion in the upper gut; colonic fermentation yields short-chain fatty acids, including butyrate, which has antineoplastic properties. 7 In carcinogen-treated rats, resistant starch reduces the development of intestinal tumors 8 , 9 and the production . . .

The phase 2 trial KEYNOTE-158 ( NCT02628067 ) evaluated pembrolizumab in microsatellite-instability-high and mismatch-repair-deficient (MSI-H/dMMR) noncolorectal tumors. With 373 participants (95% with baseline MSI/dMMR documentation) and 4.5 years of follow-up, the primary endpoint of overall response rate was 33.8%. Secondary endpoints of duration of response, overall survival and progression-free survival were 63.2, 19.8 and 4.0 months, respectively. Grade ≥3 treatment-related adverse events occurred in 50 (13%) participants. These results further support pembrolizumab use in MSI-H/dMMR tumors. Marabelle et al. present updated data from the KEYNOTE-158 trial after ~4.5 years of follow-up, reporting an overall response rate of 34% and a median overall survival of 19.8 months in participants with MSI-H/MMR advanced noncolorectal solid tumors.