Colorectal cancers diagnosed relatively soon after a colonoscopy are referred to as interval colorectal cancers.
It is not clear whether interval colorectal cancers arise from prevalent lesions missed at colonoscopy or represent specific aggressive biology leading to poor survival.
Using Danish population-based medical registries, Dr Rune Erichsen from Denmark investigated patients with “interval” colorectal cancers diagnosed within 1–5 years of a colonoscopy, and compared them with cases with colonoscopy 10 years before diagnosis and to “sporadic” colorectal cancers with no colonoscopy before diagnosis.
Multivariate logistic regression was used to explore the association between clinical, demographic, and comorbidity characteristics and interval colorectal cancers.
|The 1-year survival was 71% in sporadic cases|
|American Journal of Gastroenterology|
The comparison of the 982 interval colorectal cancers to the 358 patients with colorectal cancers 10 years after colonoscopy revealed nearly similar characteristics and mortality.
The doctors found that compared with the 35,704 sporadic colorectal cancers, interval cases were slightly older, more likely to be female, have comorbidities, have proximal tumors, and tumors with mucinous histology, but stage was similar.
The team found that female sex, localized stage at diagnosis, proximal tumor location, and high comorbidity burden were factors independently associated with interval colorectal cancers.
The 1-year survival was 68% in interval, and 71% in sporadic cases, with an adjusted MRR of 0.92.
After 5 years, survival was 41% in interval, and 43% in sporadic cases, and the adjusted 2–5 year MRR was 1.0.
Dr Erichsen's team concludes, "Clinical characteristics and survival among interval colorectal cancers did not suggest aggressive biology, but rather that the majority represented missed lesions."