Adverse events (AE) following diagnosis (Dx) in older metastatic colorectal cancer (mCRC) patients (Pts).

Abstract

e14068 Background: The relative safety of newer drugs in older pts with mCRC is understudied. The objective of this analysis is to determine factors associated with AEs in a population-based sample of older mCRC pts treated in real-world clinical settings. Methods: Pts ≥ age 65 Dx with mCRC in 2004-2007 were identified from SEER-Medicare, and excluded if they were enrolled in a Medicare HMO or lacked Medicare parts A and B. Pts who received 1st line (1L) chemotherapy (CTx) within 3 mo of Dx were dichotomized as 1L CTx alone and 1L CTx + bevacizumab (BV). Preexisting conditions (PCs) identified from claims in the 12 mo prior to start of 1L CTx were grouped into 5 categories (cardiovascular (CV), cerebrovascular (CNS), gastrointestinal (GI), tissue integrity (TI), and pulmonary (Pulm)). Claims for any of these same conditions between start of 1L CTx and end of follow-up were identified as AEs. Crude AE incidence rates were determined. Logistic regression was used to examine factors associated with BV use. Factors associated with time to 1st AE were identified in a Cox model. Results: 4,514 pts (median age 77) met inclusion, of whom 1,139 (25%) received 1L CTx only and 669 (15%) received 1L CTx + BV. BV use was less likely among pts age ≥ 75 (OR 0.35, p<0.001), non-whites (OR 0.75, p=0.002), and women (OR 0.8, p=0.001). Bev use was as likely in pts with CV, Pulm, or CNS PCs, and more likely in pts with GI (OR 1.67, p <0.001) and TI (OR 2.75, p=0.001) PCs. In a Cox model of time to 1st AE with death as a competing risk, increased risk of AE was associated with age ≥ 75 (HR 1.13, p=0.02), CNS PC (HR 1.35, p=0.02), and CV PC (HR 1.13, p=0.05). Relative to 1L CTx alone, pts receiving 1L CTx + BV did not have a higher AE risk (HR 0.89, 95% CI 0.80-0.99). AE incidence was higher in pts receiving 1L CTx alone (without subsequent biologic) (185 events / 100,000 person-days (P-D) compared with pts receiving 1L CTx + BV (139 events / 100,000 P-D). Conclusions: In this cohort, pts who received 1L CTx + BV had neither increased AE incidence nor increased risk of 1st AE compared to pts who received 1L CTx alone. PCs were not associated with decreased BV use. These data suggests BV utilization may not increase AE risk among elderly mCRC pts tx in the community.