Breast Tumors Detected Between Mammograms More Likely to Be Aggressive

Breast cancers that are first identifiable in the interval between screening mammograms are more likely to be aggressive, fast-growing tumors according to new findings.

The study's findings were published online May 3, 2011, in the Journal of the [US] National Cancer Institute. Other studies have shown that cancers diagnosed between mammograms, known as interval cancers, tend to have a worse prognosis than those detected during routine screening. This study examined the difference between "true" interval tumors--those not detectable on the earlier mammogram--and "missed" interval tumors--those not detected on the previous mammogram due to technical errors or misinterpretation.

The authors, Anna M. Chiarelli, PhD, from Cancer Care Ontario (Toronto, Canada), and colleagues, analyzed data from the Ontario Breast Screening Program for 288 women with true interval cancers and 87 women with missed interval cancers. Both kinds of interval tumors were compared to screen-detected tumors in 450 women who were similar in terms of age, location of the screening center, and length of time since their last mammogram.

As predicted, the true and missed interval tumors were of higher stage and grade than screen-detected cancers. However, true interval cancers were also more likely to be estrogen receptor-negative and progesterone receptor-negative, to have a high mitotic index, and to have a less common histology.

The investigators concluded that the findings suggest "a need for further advancement in imaging technologies to detect certain types of breast carcinomas and different approaches for early detection of fast-growing tumors."

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