Real-world time on treatment and overall survival in patients with metastatic colorectal cancer receiving cetuximab in second line after failing irinotecan or oxaliplatin-based regimens.

Abstract

e15568 Background: Anti-epidermal growth factor receptor agents are increasingly used in later lines of therapy for the treatment of metastatic colorectal cancer (mCRC). However, the real-world time on treatment (TOT) and overall survival (OS) of patients with mCRC receiving cetuximab in second-line (2L) setting have not been described. Therefore, we sought to evaluate TOT, OS and identify factors associated with longer TOT and OS based on retrospective observational data. Methods: A total of 1,011 patients were selected from the nationwide Flatiron electronic health record database (January 2013-August 2020) who were: 1) diagnosed with mCRC, 2) received 2L treatment with cetuximab containing regimens, and 3) had failed oxaliplatin/irinotecan-based regimens in first-line (1L). TOT was defined as the time from initiation of cetuximab in 2L (index date), to the last date showing evidence of cetuximab administration. End of therapy was defined if patients progressed to third-line of therapy, or having a death record. OS was calculated from the index date to the date of death or censored to last visit date available. The Kaplan-Meier estimates, and stepwise Cox models were adapted to calculate hazard ratios (HR) and 95% confidence intervals (CI) for associated factors. Results: Majority of patients receiving 2L treatment with cetuximab containing regimens were: less than 65 years old (58%), male (60%), had a median body mass index (BMI) of 26.6 kg/m², received FOLFOX regimens in 1L (61%) and were treated in the community setting (96%). The most common 2L regimens were cetuximab+FOLFIRI (46%) and cetuximab+Irinotecan (29%). Overall, the median TOT (mTOT) for patients receiving 2L cetuximab was 3.94 months (median Interquartile range (mIQR) 3.51-4.40), and median OS (mOS) was 14.36 months (mIQR 13.01-15.70). Of all cetuximab containing regimens, receiving cetuximab+FOLFIRI in 2L (mTOT = 4.43 months, mIQR 3.71-5.36), KRAS wild-type (vs. KRAS+), and receiving 2L cetuximab after prior therapy with 1L CapeOX (vs. FOLFOX) were associated with a longer mTOT. Living in the South region (vs. Midwest) was associated with a shorter mTOT. Having a higher BMI (obese vs. underweight HR = 0.46, 95% CI 0.32-0.66) was associated with a longer mOS, while receiving cetuximab+FOLFOX in 2L (mOS = 10.97 months, mIQR 5.55-14.06) or being older (≥65 vs. < 65 years; HR = 1.24, 95% CI 1.05-1.46) were associated with a shorter mOS. Conclusions: In this real-world retrospective analysis we show TOT and OS overall in mCRC patients who received cetuximab containing regimens in 2L. These patients were mostly male, < 65 years, and majority received FOLFOX regimens in 1L therapy. Key factors associated with TOT and OS were treatment regimens received in 1L and 2L. In addition, KRAS status and region were associated with TOT, while BMI and age were associated with OS only.