Invasive breast cancers are more likely to be found through breast MRI screening rather than mammography in women with elevated risk factors, according to results of a study published online April 20 in the journal Radiology.

Mammography is a critical tool in breast cancer screening, having improved patient survival rates by as much as 30 percent since the 1990s. However, additional screening with breast MRI is often recommended for women who are at an increased risk of developing the disease.

Little research has been focused on the types of cancer each modality typically detects, said lead author Janice S. Sung, MD, and her colleagues from Memorial Sloan Kettering Cancer Center in New York.

“Mammography has its limitations, especially in young women with dense breasts who are at high risk for cancer,” they wrote. “Few studies have been performed to examine the frequency of interval cancers in women at high risk who undergo screening with annual mammography and MR imaging or to correlate the biologic characteristics of breast cancers diagnosed with the method of detection.”

Sung and her team set out set out to compare breast MRI and mammography according to the clinical, imaging, and histopathologic features of the cancers they detected at screening as well as interval cancers detected between screening examinations in women with elevated breast cancer risk.

To do so, they performed a retrospective review of 7,519 high-risk women who underwent MRI screening and mammography between January 2005 and December 2010. Patient records were analyzed by age, cancer risk, tumor results, and time between diagnosis of interval cancer and most recent screening examination.

Their results showed that of 222 cancers diagnosed, 167 (75 percent) were found with MRI, 43 (19 percent) with mammography and 12 (5 percent) were interval cancers. MRI was more likely to discover invasive cancers (71 percent), while cancers diagnosed through mammography were typically calcifications or ductal carninoma in situ (88 percent).

“In women at high risk for breast cancer who underwent screening with mammography and MR imaging, invasive cancers were more likely to be detected at MR imaging, whereas most cancers detected at screening mammography were ductal carcinoma in situ,” the authors concluded. “The results of this study suggest that annual screening with breast MR imaging and mammography in women at high risk is effective for diagnosis of invasive cancers that are predominantly smaller than a centimeter and node negative."