Association between time to colonoscopy after a positive guaiac fecal test result and risk of colorectal cancer and advanced stage disease at diagnosis

We evaluated time to colonoscopy after a positive guaiac-based fecal occult blood test (gFOBT) result and its association with the risk of overall colorectal cancer (CRC) and advanced-stage disease at diagnosis. We conducted a retrospective cohort study (2011-2013) within the Clalit Health Services, Israel. Participants were patients between 50 and 74 years old with a positive gFOBT result who had follow-up colonoscopies within 24 months. The exposure was time to colonoscopy, and the main outcome measure was a risk for overall and advanced CRC (defined as Stages III-IV). Odds ratios (ORs) and 95% confidence intervals (CIs) were adjusted for patient demographics and baseline risk factors. Of the 17,958 patients with positive gFOBT results (median age, 61 years [interquartile range, 56-67 years]; women, 52.2%), there were 685 cases of CRC and 156 cases of an advanced-stage disease diagnosed. The rate of cancer diagnosis at 0-3, 4-6, 7-9, 10-12 and 13-24 months was 3.9%, 2.5%, 3.5%, 4.2% and 7.3%, respectively (p < 0.001). Compared to colonoscopy follow-up within 0-3 months, risks for any CRC and advanced stage disease were higher for a follow-up of 12-24 months: OR, 1.97 (95% CI, 1.51-2.56) and 1.88 (95% CI, 1.43-2.46), respectively. For right-sided cancer (n = 194), an increased risk starts at 10 months, OR, 1.91 (95% CI 1.03-3.56). A result of 3-6 positive fields was significantly associated diagnosis of cancer (OR, 5.52; 95% CI, 4.71-6.46) and advanced stage disease (OR, 8.07; 95% CI, 5.74-11.36). Encouraging an early uptake of colonoscopy and targeting those with 10-24 months delay and a 3-6 positive fields is warranted.