Does delaying adjuvant chemotherapy after curative surgery for colorectal cancer impair survival? A meta-analysis

In stage III colorectal cancer (CRC), adjuvant chemotherapy (CT) is usually prescribed within two months after curative surgery. Whether or not delaying initiation of CT affects survival is still debated.

We performed a meta-analysis (MA) of all published studies (full papers or abstracts) comparing delayed CT with standard care. Studies were obtained from a PubMed query (keywords: CRC, adjuvant treatment, delay of CT), a review (Chau et al., 2006), cross-checking references and abstracts from the proceedings of ASCO, ASCO GI and WCGI annual meetings. We chose a cutoff delay of 8 weeks. Risk Ratios (RRs) were calculated from the recorded events (deaths, relapses). We used EasyMA software (fixed-effect model).

Fourteen studies (including four abstracts) were identified (17,645 patients; 5,952 males, 5,151 females, mean age 70 years). Of these, three could not be statistically analysed and three used another cutoff (4, 5 or 6 weeks), leaving 8 studies for main MA (13,158 patients; 3,932 males, 3,644 females, 5,942 missing data; 5,576 colon cancers, 6,677 rectal, 1,265 missing data). Delaying CT more than 8 weeks was associated to worse Overall Survival (OS) (RR: 1.20; 95% Confidence Interval (CI) 1.15-1.26). In the MA including all studies whatever their cutoff, longer delay was similarly associated to a worse OS but not a worse Relapse-Free Survival (RFS) (five studies).

Adjuvant chemotherapy should be started within 8 weeks after surgery. Delaying the initiation of adjuvant CT for more than 8 weeks after surgery significantly decreased OS but not RFS. This discrepancy might be due to factors not directly related to cancer (post-operative complications, social status) or to a more accurate appraisal of death.