ASPO Abstracts
Abnormal Stool Blood Tests and Colorectal Cancer Mortality in a Large United States Cohort
Category: Early Detection & Risk Prediction
Conference Year: 2020
Abstract Body:
Purpose: Our aim was to examine the association between fatal colorectal cancer (CRC) and
time to colonoscopy among individuals who underwent diagnostic colonoscopy after abnormal
stool blood test (SBT) in a cohort of United States Veterans.
Methods: We performed a cohort study of Veterans aged 50-75 years, with an abnormal SBT
using the Veterans Health Administration’s (VA) national electronic health record data during the
years 1999 and 2010. Colonoscopy receipt was ascertained using current procedural terminology
codes after abnormal SBT. The study outcome, CRC death, was defined through National Death
Index cause-specific mortality data. We followed patients through CRC-related death, other
death, or until December 31, 2015. Multivariable Cox proportional hazards modeling was used to
generate CRC-specific mortality hazard ratios (HRs) and 95% confidence intervals (CI) for 3-
month colonoscopy intervals, with 3-6 months as the reference. Models were adjusted for age,
sex, race/ethnicity, smoking, diabetes, body mass index, and Charlson Comorbidity Index.
Results: We included 222,004 patients with abnormal SBTs; the average age was 63 with a
standard deviation of 7.2 years, 97% were male, 72% were Non-Hispanic White and 20% were
Black. Of the 222,004 patients, 69% completed diagnostic colonoscopy within 12 months of
abnormal SBT, 4% were diagnosed with CRC, and 1% died of CRC specific death. Compared to
patients with a colonoscopy at 3-6 months (standard of care), CRC-related mortality risk was
significantly higher for patients with colonoscopies at 0-3 months (HR=1.29; 95% CI, 1.14-1.47),
18-21 months (HR=1.57; 95% CI,1.19-2.06), and 21-24 months (HR=1.46; 95% CI, 1.07-1.97).
No significant increase in mortality risk was shown for 6-9 month, 9-12 month, 12-15 month, 15-
18 months, and 24+ month intervals.
Conclusion: Time to colonoscopy plays a significant role in CRC death after abnormal SBT.
Compared to a colonoscopy performed during a 3-6-month window, a colonoscopy performed
outside of the 15-month window had a higher risk for mortality. Given the impact of timely
diagnostic colonoscopy on CRC mortality, development of interventions to increase timely
diagnostic follow-up after abnormal SBT are essential to CRC outcome improvement.
Keywords: Colorectal cancer, mortality, screening