Breast cancers detected in the interval between screening mammograms tend to have more aggressive characteristics than cancers detected during screening mammography. These results were published in the Journal of the National Cancer Institute.
Interval breast cancers refer to breast cancers that are detected in between screening mammograms. Previous studies have suggested that interval cancers are faster growing than cancers that are detected by routine mammography.
The current study built upon these findings by distinguishing “true” interval cancers (cancers that were not detectable at the time of the previous mammogram) from “missed” interval cancers (cancers that were detectable at the time of the previous mammogram, but were missed). Information was collected about 288 women with true interval cancers, 87 women with missed interval cancers, and 450 women with screen-detected cancers (cancers detected during routine screening mammography).
Compared with screen-detected cancers, both true and missed interval cancers had a higher stage and higher grade at diagnosis.
- True interval cancers were also more likely to have a high mitotic index (a marker of rapid cell division), to be negative for both estrogen receptors and progesterone receptors, and to involve less common types of breast cancer.
These results provide additional evidence that interval cancers (particularly true interval cancers) tend to have worse prognostic features than screen-detected cancers. The researchers conclude “The findings suggest a need for more sensitive screening modalities to detect true interval breast cancers and different approaches for early detection of the fast-growing tumors.”
Reference: Kirsh VA, Chiarelli AM, Edwards SA et al. Tumor characteristics associated with mammographic detection of breast cancer in the Ontario Breast Cancer Screening Program. Journal of the National Cancer Institute. Early online publication May 3, 2011.