Women diagnosed with interval breast cancers — those detected between routine screenings — had a higher risk for aggressive disease and death, a restrospective study in Canada indicated.

Among women participating in a national screening program, and with a median follow-up of 7 years, breast cancer-specific mortality was more than threefold higher for women diagnosed with interval breast cancers compared to those whose cancers were found on screening, which included a sojourn time of 2 years to account for lead-time bias (hazard ratio [HR] 3.55, 95% CI 2.01-6.28, P<0.001), reported Saroj Niraula, MD, MSc, of the University of Manitoba in Canada, and colleagues.

The findings highlight the differences in the natural history of these cancers “and highlights inadequacies in current breast cancer screening practice,” the group wrote in JAMA Network Open. “Many of the aggressive and lethal forms of breast cancers either go unnoticed on mammogram or develop