Biomarker testing patterns among patients with early and late-onset metastatic colon cancer.

Abstract

e15575 Background: Molecular testing is essential in considering targeted therapies, particularly for the increasing number of metastatic colon cancer (mCC) patients (pts) diagnosed at younger ages who may present with more aggressive disease. This analysis compares demographic and clinical characteristics, and biomarker testing and positivity rates of mCC pts diagnosed at younger versus older ages. Methods: We analyzed 1029 pts with mCC (stage IV at diagnosis) between 01/01/2016 - 12/31/2020 who received care in community health systems in the United States. Pts 18-49 years at mCC diagnosis were considered early onset (EO), and those 50 or older were considered late onset (LO). We compared the distributions of year at diagnosis, gender, race/ethnicity, smoking status, histology, stage at diagnosis, tumor sidedness, KRAS, NRAS, and BRAF testing, and positivity rates between EO and LO mCC pts. Differences in distributions were assessed using chi-square tests. Results: EO pts (n = 148) were more likely to have left-sided tumors than LO pts (n = 881, 55% vs. 36%; p-value < 0.001), and were less likely to be ever smokers (24% vs. 40%; p-value < 0.001); the remaining demographic and clinical characteristics were similar between the two groups. Testing was significantly more common among EO than LO pts for KRAS (71% vs 48%), NRAS (39% vs 29%), and BRAF (41% vs 31%) (Table). Annual NRAS and BRAF testing rates increased between 2016 - 2020 for both groups: NRAS rates increased from 13% to 41%, and 5% to 37%, for EO and LO pts, respectively; BRAF rates increased from 13% to 41%, and 5% to 40%, for EO and LO pts, respectively. KRAS testing rates held at a consistent rate over time for EO pts, and increased over time among LO mCC pts (35% - 52%). The positivity rates for KRAS, NRAS and BRAF mutations were similar among tested pts in both groups. Conclusions: In this real world analysis, pts with EO mCC were more likely to have left sided primary cancers, and less likely to have a smoking history. Of note, BRAF testing showed a marked increase over time among all mCC pts. EO pts were more likely to receive KRAS, NRAS and BRAF testing. Further understanding of the correlates of EO mCC, biomarker testing practices, and subsequent treatment decisions is critical to improving pt outcomes.[Table: see text]