In comparison with CrD-SBC, CD-SBC patients harbour MSI and high TILs more frequently and show better outcome. This seems mainly due to their higher TIL density, which at multivariable analysis showed an independent prognostic value. MSI/TIL status, KRAS mutations and HER2 amplification might help in stratifying patients for targeted anti-cancer therapy.

Purpose: BRAF mutations are grouped in activating RASindependent signaling as monomers (class 1-V600E) or as dimers (class 2-codons 597/601), and RAS-dependent with impaired kinase activity (class 3-codons 594/596). Although clinical, pathologic, and molecular features of V600E BRAFmutated metastatic colorectal cancer (mCRC) are well known, limited data are available from the two other classes. Experimental Design: Data from 117 patients with BRAF (92 class 1, 12 class 2, and 13 class 3)-mutated mCRC were collected. A total of 540 BRAF wt mCRCs were included as control. IHC profiling was performed to determine the consensus molecular subtypes (CMS), cytokeratin 7/20 profiles, tumor-infiltrating lymphocyte infiltration, and BM1/BM2 categorization. Overall survival (OS) and progression-free survival were evaluated by Kaplan-Meier and log-rank test. Results: Class 3 BRAF-mutated mCRC was more frequently left sided (P ¼ 0.0028), pN0 (P ¼ 0.0159), and without peritoneal metastases (P ¼ 0.0176) compared with class 1, whereas class 2 cases were similar to class 1. Hazard ratio for OS, as compared with BRAF wt, was 2.38 [95% confidence interval (CI), 1.61-3.54] for class 1, 1.90 (95% CI, 0.85-4.26) for class 2, and 0.93 (95% CI, 0.51-1.69) for class 3 (P < 0.0001). Class 2 and 3 tumors were all assigned to CMS2-3. A higher median CD3/CD8-positive lymphocyte infiltration was observed in BRAF-mutated class 2 (P ¼ 0.033) compared with class 3 cases. Conclusions: For the first time, different clinical and pathologic features and outcome data were reported according to the three BRAF mutation classes in mCRC. Specific targeted treatment strategies should be identified in the near future for such patients.

ConclusionFCM seems to be a promising tool for enhanced specimens' reporting performance, given its simple application and very rapid microscopic image generation (<5 min/specimen). This technique may potentially be used for intraoperative pathological specimens' analysis.

Background Immunotherapy with immune checkpoint inhibitors (ICIs) is highly effective in microsatellite instability–high (MSI‐H) metastatic colorectal cancer (mCRC); however, specific predictive biomarkers are lacking. Patients and Methods Data and samples from 85 patients with MSI‐H mCRC treated with ICIs were gathered. Tumor infiltrating lymphocytes (TILs) and tumor mutational burden (TMB) were analyzed in an exploratory cohort of “super” responders and “clearly” refractory patients; TILs were then evaluated in the whole cohort of patients. Primary objectives were the correlation between the number of TILs and TMB and their role as biomarkers of ICI efficacy. Main endpoints included response rate (RR), progression‐free survival (PFS), and overall survival (OS). Results In the exploratory cohort, an increasing number of TILs correlated to higher TMB (Pearson's test, p = .0429). In the whole cohort, median number of TILs was 3.6 in responders compared with 1.8 in nonresponders (Mann‐Whitney test, p = .0448). RR was 70.6% in patients with high number of TILs (TILs‐H) compared with 42.9% in patients with low number of TILs (odds ratio = 3.20, p = .0291). Survival outcomes differed significantly in favor of TILs‐H (PFS: hazard ratio [HR] = 0.42, p = .0278; OS: HR = 0.41, p = .0463). Conclusion A significant correlation between higher TMB and increased number of TILs was shown. A significantly higher activity and better PFS and OS with ICI in MSI‐H mCRC were reported in cases with high number of TILs, thus supporting further studies of TIL count as predictive biomarker of ICI efficacy. Implications for Practice Microsatellite instability is the result of mismatch repair protein deficiency, caused by germline mutations or somatic modifications in mismatch repair genes. In metastatic colorectal cancer (mCRC), immunotherapy (with immune checkpoint inhibitors [ICIs]) demonstrated remarkable clinical benefit in microsatellite instability–high (MSI‐H) patients. ICI primary resistance has been observed in approximately 25% of patients with MSI‐H mCRC, underlining the need for predictive biomarkers. In this study, tumor mutational burden (TMB) and tumor infiltrating lymphocyte (TIL) analyses were performed in an exploratory cohort of patients with MSI‐H mCRC treated with ICIs, demonstrating a significant correlation between higher TMB and increased number of TILs. Results also demonstrated a significant correlation between high number of TILs and clinical responses and survival benefit in a large data set of patients with MSI‐H mCRC treated with ICI. TMB and TILs could represent predictive biomarkers of ICI efficacy in MSI‐H mCRC and should be incorporated in future trials testing checkpoint inhibitors in colorectal cancer.