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Background: The majority of pancreatic ductal adenocarcinomas (PDACs) are driven by mutant (mt) KRAS. How mt KRAS and co-driver mutations affect the immune cell (IC) landscape of PDAC remains uncertain. Herein, we characterize the types of IC in the PDAC tumor microenvironment (TME) and the prevalence of immuno-oncologic (IO) biomarkers by genomic and transcriptomic analysis in the context of KRAS status. Materials and methods: 4142 PDAC and 3727 colorectal cancer (CRC) cases with KRAS mt were analyzed using next-generation DNA sequencing, immunohistochemistry, and whole-transcriptome RNA sequencing. Microsatellite instability and deficiency in mismatch repair (MSI-H/dMMR) and tumor mutational burden (TMB) were also assessed. Results: We found KRAS mt in 81% of PDAC, with the most common variant being G12D in PDAC, and fewer cases of KRAS mt were co-expressed with the predictive IO marker MSI-H/dMMR than KRAS-wild-type (wt). However, KRASG12D, KRASG12V, and KRASQ61 mutations had significantly lower TMB than KRAS wt tumors in PDAC. The IC environment of KRAS mt PDAC showed significant differences in nearly all IC types; a similar pattern was observed in CRC but was less pronounced. Conclusions: Therapeutic IO targets like programmed death-ligand 1 are enriched in pancreatic adenocarcinoma cases harboring specific targetable variants of KRAS mt PDAC. Better understanding of the TME could lead to tailored immunotherapeutic strategies to overcome these barriers in KRAS mt PDAC, possibly in combination with molecularly targeted treatment strategies.

Background: Since 2004, a regimen of 6 months of treatment with oxaliplatin plus a fluoropyrimidine has been standard adjuvant therapy in patients with stage III colon cancer. However, since oxaliplatin is associated with cumulative neurotoxicity, a shorter duration of therapy could spare toxic effects and health expenditures., Methods: We performed a prospective, preplanned, pooled analysis of six randomized, phase 3 trials that were conducted concurrently to evaluate the noninferiority of adjuvant therapy with either FOLFOX (fluorouracil, leucovorin, and oxaliplatin) or CAPOX (capecitabine and oxaliplatin) administered for 3 months, as compared with 6 months. The primary end point was the rate of disease-free survival at 3 years. Noninferiority of 3 months versus 6 months of therapy could be claimed if the upper limit of the two-sided 95% confidence interval of the hazard ratio did not exceed 1.12., Results: After 3263 events of disease recurrence or death had been reported in 12,834 patients, the noninferiority of 3 months of treatment versus 6 months was not confirmed in the overall study population (hazard ratio, 1.07; 95% confidence interval [CI], 1.00 to 1.15). Noninferiority of the shorter regimen was seen for CAPOX (hazard ratio, 0.95; 95% CI, 0.85 to 1.06) but not for FOLFOX (hazard ratio, 1.16; 95% CI, 1.06 to 1.26). In an exploratory analysis of the combined regimens, among the patients with T1, T2, or T3 and N1 cancers, 3 months of therapy was noninferior to 6 months, with a 3-year rate of disease-free survival of 83.1% and 83.3%, respectively (hazard ratio, 1.01; 95% CI, 0.90 to 1.12). Among patients with cancers that were classified as T4, N2, or both, the disease-free survival rate for a 6-month duration of therapy was superior to that for a 3-month duration (64.4% vs. 62.7%) for the combined treatments (hazard ratio, 1.12; 95% CI, 1.03 to 1.23; P=0.01 for superiority)., Conclusions: Among patients with stage III colon cancer receiving adjuvant therapy with FOLFOX or CAPOX, noninferiority of 3 months of therapy, as compared with 6 months, was not confirmed in the overall population. However, in patients treated with CAPOX, 3 months of therapy was as effective as 6 months, particularly in the lower-risk subgroup. (Funded by the National Cancer Institute and others.).