Background: A fecal test followed by diagnostic colonoscopy for a positive result is a widely endorsed screening strategy for colorectal cancer (CRC). However, the relationship between the time delay from the positive test to the follow-up colonoscopy and CRC mortality has not been established.
Methods: From a population-based screening program, we identified CRC patients newly diagnosed from 2005 through 2015 by a positive fecal occult test followed by a colonoscopy. The primary outcome measure was CRC-specific mortality according to four categories for the time elapsed between the positive result and the subsequent colonoscopy.
Results: The 1749 patients underwent colonoscopies within 0-3 months (n = 981, 56.1%), 4-6 months (n = 307, 17.5%), 7-12 months (n = 157, 9.0%), and later than 12 months (n = 304, 17.4%). CRC-specific deaths according to exposure groups were: 13.8% (135 of 981) for 0-3 months, 10.7% (33 of 307) for 4-6 months (crude hazards ratio [HR] = 0.74, 95% confidence interval [CI] = 0.51 to 1.14), 11.5% (18 of 157) for 7-12 months (crude HR = 0.83, 95% CI = 0.51 to 1.42), and 22.7% (69 of 304) for longer than 12 months (crude HR = 1.40, 95% CI = 1.04 to 1.90). The only variable that was associated with mortality risk was the number of positive slides (P = .003). High positivity was twice the value in the 0-3 as the longer-than-12 months group: 51.9% vs 25.0% and similar for the 4-6 and 7-12 months groups (38.1% and 36.5%), respectively. The adjusted HRs for CRC mortality were 0.81 (95% CI = 0.55 to 1.19); 0.83 (95% CI = 0.50 to 1.41), and 1.53 (95% CI = 1.13 to 2.12, P = .006) for the 4-12, 7-12, and longer-than-12-months groups, respectively, compared with the shortest delay group.
Conclusions: Among screen-diagnosed CRC patients, performance of colonoscopy more than 12 months after the initial positive fecal occult blood test was associated with more advanced disease and higher mortality due to CRC.