Excess mortality after curative surgery for colorectal cancer changes over time and differs for patients with colon versus rectal cancer

Abstract

Background. Improved management of colorectal cancer patients has resulted in better five-year survival for rectal cancer compared with colon cancer. We compared excess mortality rates in various time intervals after surgery in patients with colon and rectal cancer. Material and methods. We analysed all patients with curative resection of colorectal cancers reported in the Cancer Registry of Norway before (1994–1996) and after (2001–2003) national treatment guidelines were introduced. Excess mortality was analysed in different postoperative time intervals within the five-year follow-up periods for patients treated in 1994–1996 vs. 2001–2003. Results. A total of 11 437 patients that underwent curative resection were included. For patients treated from 1994 to 1996, excess mortality was similar in colon and rectal cancer patients in all time intervals. For those treated from 2001 to 2003, excess mortality was significantly lower in rectal cancer patients than in colon cancer patients perioperatively (in the first 60 days: excess mortality ratio = 0.46, p = 0.007) and during the first two postoperative years (2–12 months: excess mortality ratio = 0.54, p = 0.010; 1–2 years: excess mortality ratio = 0.60, p = 0.009). Excess mortality in rectal cancer patients was significantly greater than in colon cancer patients 4–5 years postoperatively (excess mortality ratio = 2.18, p = 0.003). Conclusion. Excess mortality for colon and rectal cancer changed substantially after the introduction of national treatment guidelines. Short-term excess mortality rates was higher in colon cancer compared to rectal cancer for patients treated in 2001–2003, while excess mortality rates for rectal cancer patients was significantly higher later in the follow-up period. This suggests that future research should focus on these differences of excess mortality in patients curatively treated for cancer of the colon and rectum.

Acknowledgements

We are very grateful to Maja Pohar Perme, Ph.D. for valuable discussions on excess mortality calculations and use of the relsurv statistical package. A part of the results were presented at the Excellence in Oncology Congress, Athens, Greece, 2010. In conjunction with the presentation, those results were published in abstract form in the Int J Cancer Supplement 1, March 2011 as Abstract OP 05.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

This study was funded by the Folke Hermansen Cancer Research Foundation (grant no. 424401).