Survival trends and patterns of chemotherapy use in elderly metastatic colorectal cancer (mCRC) patients.

Abstract

6118 Background: Since 2002, several drugs (including bevacizumab (Bv), oxaliplatin (Ox), irinotecan (Iri)) have been approved for mCRC. The goals of this study are to examine patterns of newer chemotherapy (CTx) use and survival trends in older mCRC pts. Methods: Pts ≥ age 65 with mCRC diagnosis (dx) 2001–5 were identified from the SEER–Medicare database. Pts were excluded for Medicare HMO, lack of Medicare parts A and B, or second cancer. First–line (1L) CTx was identified within 3 mo of dx. Pts were categorized by dx year (2001–3 vs. 2004–5) and treatment (none, CTx, CTx + Bv.). A logistic regression model identified factors associated with 1L Bv use. A Cox proportional hazards regression model was used to assess association of various factors (age, comorbidity, hepatic resection (rsxn), CTx) with survival. Results: 5,725 pts (median age 77) met criteria, of whom 2,647 (46%) received 1L CTx. In 2004–5, 32% and 12% of treated pts received Ox and Iri (vs.1% and 34% in 2001–3). Following its approval in 2004, 25% of treated pts received Bv. Factors associated with 1L Bv use include age <75 (OR 1.43, p=0.02) and concurrent use of Ox (OR 10.11, p<0.001) or Iri (OR 5.82, p<0.001). In a Cox proportional hazards model, survival was greater in pts with lower comorbidity, age <75, hepatic rsxn, 1L CTx use, and dx 2004–5. Pts dx 2004–5 who used Bv had the greatest survival compared with untreated pts dx 2001–3 (HR 0.46, p<0.001, median OS 15 vs. 6 mo). Conclusions: In an elderly mCRC cohort, nearly half of pts received 1L CTx, many with regimens containing Iri, Ox, or Bv. Survival was greatest in pts dx 2004–5 who used Bv. Increased Ox use may also have improved survival in this period. Future SEER–Medicare analyses may help elucidate the relative benefit of other new agents in the elderly, a population under–represented in clinical trials. Cox proportional hazards model. Factor HR 95% CI P Age < 75 0.71 0.66 – 0.75 <0.001 Comorbidity (Klabunde) ≤ 1 0.75 0.70 – 0.80 <0.001 Hepatic rsxn 0.68 0.58 – 0.79 <0.001 Dx 2001-3 + 1L CTx 0.84 0.78 – 0.91 <0.001 Dx 2004-5 no 1L CTz 0.88 0.81 – 0.95 0.002 Dx 2004-5 + 1L CTx 0.63 0.57 – 0.69 <0.001 Dx 2004-5 + 1L CTx and Bv 0.46 0.39 – 0.55 <0.001 Reference: Age ≥ 75. Comorbidity >1, No hepatic rsxn, Dx 2001-3 no 1L CTx