True Interval Breast Cancers May Have Aggressive Features
True interval cancers have adverse prognostic features compared with screen-detected cancers
MONDAY, May 9 (HealthDay News) -- True and missed interval cancers are more likely to have a higher grade and stage compared with screen-detected breast cancers, and true interval cancers have additional adverse prognostic features, according to a study published online May 3 in the Journal of the National Cancer Institute.
Victoria A. Kirch, Ph.D., from Cancer Care Ontario in Toronto, and colleagues compared the prognostic value of tumor characteristics according to type of breast cancer diagnosed in the interval between mammographic screenings. A cohort of 431,480 women in the Ontario Breast Screening Program, aged 50 years and older, underwent screening between 1994 and 2002. A total of 288 breast cancers diagnosed within 24 months following a negative screening mammogram (true interval cancers), and 87 cancers that were not identified at the time of screening but were identified in retrospect (missed interval cancers), were matched with 450 screen-detected cancers. Tumors were evaluated for stage, grade, mitotic index, histology, and hormone receptor expression.
The investigators found that both true and missed interval cancers were of higher stage and grade compared with screen-detected cancers. Compared with screen-detected cancers, true interval cancers had a significantly increased mitotic index (odds ratio [OR], 3.13), had a significantly increased percentage of nonductal histology (OR, 1.94), and were significantly more likely to be both estrogen and progesterone receptor-negative (OR, 2.09 and 2.49, respectively).
"Both true and missed interval cancers were of higher stage and grade than were screen-detected cancers. However, compared with screen-detected cancers, true interval cancers were more likely to have additional adverse prognostic features," the authors write.