Author Affiliations: Mayo Clinic, Rochester, Minnesota (Drs Sargent and Grothey) (firstname.lastname@example.org); and University of Birmingham, Birmingham, Alabama (Mr Gray).
To the Editor: We do not believe that the conclusion by Dr Biagi and colleagues that survival was compromised by later initiation of adjuvant chemotherapy for colorectal cancer1 is justified by the data presented. The poorer survival in patients starting chemotherapy at later times observed in their meta-analysis of observational studies could be explained by patients with significant comorbidities recovering less quickly from surgery and thus starting chemotherapy later. Indeed, the Adjuvant Colon Cancer Endpoints Group (ACCENT)2 had previously discussed performing a similar analysis of our much larger, individual patient database from randomized trials, but the trial groups represented agreed that such an analysis would be so seriously biased by confounding factors (eg, age, comorbidities) that it would likely be more misleading than informative.
Sargent D, Grothey A, Gray R. Time to Initiation of Adjuvant Chemotherapy and Survival in Colorectal Cancer. JAMA. 2011;306(11):1199-1200. doi:10.1001/jama.2011.1319