Clinical Implication of KRAS Mutation Variants in Patients With Resected Colon Cancer

Aim: This study evaluated the clinical implication of KRAS proto-oncogene, GTPase (KRAS) mutation variants in patients with resected colon cancer (CC). Patients and Methods: We retrospectively reviewed 482 patients diagnosed with CC who underwent curative surgical resection at Kyungpook National University Chilgok Hospital. The inclusion criteria were: Pathologically diagnosed with primary CC; stage I-III CC according to the 7th edition of American Joint Committee on Cancer staging system; and with available test results for KRAS mutation status. In total, 345 patients met these criteria and were included in this study. Results: Among the 345 patients, 140 (40.6%) exhibited KRAS mutations, with their incidences as follows: 90/140 (64.3%) in exon 2 codon 12, 37/140 (26.4%) in exon 2 codon 13, 1/140 (0.1%) in exon 3 codon 59, 7/140 (5.0%) in exon 3 codon 61, and 5/140 (3.6%) in exon 4 codon 146. KRAS mutation status was not a significant prognostic factor for disease-free survival or overall survival. Although there were no significant differences in survival between patients with exon 2 codon 12 and exon 2 codon 13 mutations, poorer disease-free survival (p=0.085) and overall survival (p=0.005) were seen in those with exon 3 codon 61 mutation than in others. Conclusion: KRAS mutation status was not correlated with survival, but exon 3 codon 61 mutation might be a factor for poor prognosis in patients after resection of CC.

Discordance of KRAS Mutational Status between Primary Tumors and Liver Metastases in Colorectal Cancer: Impact on Long-Term Survival Following Radical Resection

If KRAS mutation status of primary colorectal tumor is representative of corresponding colorectal liver metastases (CRLM) mutational pattern, is controversial. Several studies have reported different rates of KRAS discordance, ranging from 4 to 32%. Aim of this study is to assess the incidence of discordance and its impact on overall survival (OS) in a homogenous group of patients. KRAS mutation status was evaluated in 107 patients resected for both primary colorectal tumor and corresponding CRLM at the same institution, between 2007 and 2018. Discordance rate was 15.9%. Its incidence varied according to the time interval between the two mutation analyses (p = 0.025; Pearson correlation = 0.2) and it was significantly higher during the first 6 months from the time of primary tumor evaluation. On multivariable analysis, type of discordance (wild-type in primary tumor, mutation in CRLM) was the strongest predictor of poor OS (p < 0.001). At multivariable logistic regression analysis, the number of CRLM >3 was an independent risk factor for the risk of KRAS discordance associated with the worst prognosis (OR = 4.600; p = 0.047). Results of our study suggested that, in the era of precision medicine, possibility of KRAS discordance should be taken into account within multidisciplinary management of patients with metastatic colorectal cancer.

Subgroup analyses of patients (pts) with microsatellite instability-high/mismatch repair-deficient (MSI-H/dMMR) metastatic colorectal cancer (mCRC) treated with nivolumab (NIVO) plus low-dose ipilimumab (IPI) as first-line (1L) therapy:Two-year clinical update.

58 Background: In the phase 2 CheckMate 142 trial, NIVO + low-dose IPI had robust, durable clinical benefit and was well tolerated as 1L therapy for MSI-H/dMMR mCRC (median follow-up, 29.0 months [range, 24.2–33.7]) (Lenz et al. J Clin Oncol 2020;38:Abstract 4040; NCT02060188). Objective response rate (ORR) per investigator (INV) was achieved in 69% of pts (95% CI, 53–82); progressive disease rate was 13%. Median progression-free survival (PFS) and overall survival (OS) were not reached. Median duration of treatment was 19.1 months (95% CI, 11.1–29.0). Grade 3–4 treatment-related adverse events (TRAEs) occurred in 22% of pts. We present the post hoc subgroup analyses of efficacy and safety outcomes in pts from the same follow-up based on demographics and baseline disease characteristics. Methods: Pts with MSI-H/dMMR mCRC and no prior treatment for metastatic disease received NIVO 3 mg/kg Q2W + low-dose IPI 1 mg/kg Q6W until disease progression or discontinuation. ORR (primary endpoint, RECIST v1.1) and PFS were assessed per INV. Post hoc subgroup analyses of efficacy (by ECOG performance status [PS], stage at initial diagnosis, primary tumor location, and BRAF/KRAS mutation status) and safety (by age and ECOG PS) are presented. Results: Among 45 treated pts, efficacy (Table) and safety were generally consistent across evaluated subgroups. ORR was similar in pt subgroups by BRAF/ KRAS mutation status, stage at initial diagnosis, primary tumor location, and ECOG PS (Table). Median PFS and OS were not reached (NR) in evaluated subgroups after a minimum follow-up of 24.2 months (Table). Incidence of grade 3–4 TRAEs for subgroups by age and ECOG PS were consistent with the overall population. Conclusions: NIVO + low-dose IPI demonstrated robust, durable clinical benefit; was well tolerated with 2-year follow-up; and was consistent in evaluated subgroups in 1L MSI-H/dMMR mCRC. Clinical trial information: NCT02060188. [Table: see text]

BIOM-06. CLINICAL AND PROGNOSTIC SIGNIFICANCE OF KRAS MUTATIONS FOR BRAIN METASTASES FROM COLORECTAL ADENOCARCINOMA IN THE UNITED STATES

BACKGROUND KRAS mutations in colorectal adenocarcinomas have been associated with metastatic involvement of the brain (BM); and predict a lack of benefit to EGFR-targeted antibodies. Herein we leverage national data to evaluate the prevalence and impact of KRAS mutations on colorectal BMs. METHODS Newly-diagnosed patients with stage 4 colorectal adenocarcinoma were identified from the National Cancer Database, comprising &gt;70% of newly-diagnosed cases in the U.S. from 2010–2016. Multivariable logistic regression was used to evaluate predictors of brain involvement, including KRAS mutation status. Overall survival (OS) was estimated with Kaplan-Meier techniques, and compared by logrank test and multivariable Cox regression. RESULTS Of 86,719 patients newly presenting with stage 4 colorectal adenocarcinoma, 1.5% (n=1,318) had BMs. 39.7% of BM cases had KRAS mutation testing, in which 57.9% (n=361) of BM cases were KRAS-mutant, as opposed to only 45.6% (n=13,259) of non-BM cases (p&lt; 0.001). Mutant KRAS persisted as independently associated with BMs (OR 1.37, 95%CI: 1.09–1.72, p=0.006) following adjustment for age at diagnosis, sex, AJCC cT and cN status, and metastatic lung, liver, or bone involvement. Overall, BM patients displayed a median OS of 5.3 months (95%CI: 4.6–6.1): 7.5 months (95%CI: 5.7–10.6) if KRAS-wildtype vs. 12.0 months (95%CI: 10.4–15.4) if KRAS-mutant (p=0.01). The improved OS associated with KRAS-mutant BMs also persisted (HR 0.63, 95%CI: 0.47–0.84, p=0.001) after adjusting for the aforementioned clinical variables, in addition to comorbidity index, chemoradiotherapy, metastasectomy, and treating hospital type. CONCLUSIONS Nationally, testing colorectal BM patients for KRAS mutation status—a predictive biomarker for EGFR-mab therapy—remains underutilized. KRAS-mutant colorectal adenocarcinomas were more likely to have metastatic brain involvement, with KRAS-wildtype BMs demonstrating significantly worse OS than KRAS-mutant BMs. Our data suggest that KRAS mutation testing is underutilized in colorectal BM patients and provides useful prognostic information.