Metachronous colorectal cancer: a competing risks analysis with consideration for a stratified approach to surveillance colonoscopy.

BACKGROUND

The incidence of metachronous cancer will become an important clinical consideration as the life expectancy of the population increases and as rates of curative resection improve.

OBJECTIVE

To assess the pattern of metachronous cancer development following curative resection of colorectal cancer in an unselected patient population offered postoperative colonoscopic surveillance.

METHOD

Prospective clinical follow-up after curative colorectal cancer resection and surveillance colonoscopy with or without polypectomy in accordance with the national guidelines. Actuarial analysis and competing risk analysis were performed to account for death and recurrence and to stratify for age, gender, stage, and tumor site.

RESULTS

Five hundred thirty-eight patients with median follow-up 4 years 2 month (0-16) years. Fifteen patients (3%) developed metachronous cancer, at a median time interval of 90 months from primary resection. Thirteen metachronous cancer patients (87%, 13/15) underwent one to five surveillance colonoscopies: nine patients were asymptomatic at time of diagnosis of metachronous cancer. Competing risks analysis suggests that the adjusted cumulative incidence in males aged 55 is 4% at 10 years compared with 1% in females aged 85 years old.

CONCLUSIONS

A patient aged under 65 at the time of the primary curative resection carries a 2% 5-year risk of metachronous cancer, implying that 3 year surveillance colonoscopy is justified. Whereas patients aged over 75 carry less than a 2% 10-year risk, implying that it is seldom warranted to repeat the colonoscopy more frequently than every 5 years. A stratified approach to the frequency of surveillance colonoscopy requires further consideration.