Alternating Mammography and MRI for Breast Cancer Detection

Alternating mammography and MRI every 6 months appears to be the best way to detect cancer in high-risk women, an M.D. Anderson study found. This strategy can identify cancers not found by mammography alone, said Huong Le-Petross, MD, assistant professor, Diagnostic Radiology, who presented a retrospective pilot study at a poster session during the San Antonio Breast Cancer Symposium.

“Standard of practice for high-risk women is to perform mammography and MRI every year at the same time. We wanted to see if imaging women every 6 months with alternating modalities would improve detection yield,” she said.

The study was based on a retrospective chart review of 334 women who participated in a high-risk breast cancer-screening program from January 1997 to December 2007 and had one to four MRI screening cycles. Women were deemed high risk if they had hereditary breast and ovarian cancer syndrome, a personal history of breast cancer, a biopsy indicating atypia or lobular carcinoma in situ, or a 20% or higher lifetime risk of developing breast cancer according to the Gail Model.

Of these women, 86/334(26%) underwent alternate mammography/MRI alternating every 6 months. The other 248 women either had prophylactic mastectomy or initiated chemoprevention strategies. All study participants had a clinical breast exam every 6 months. Median follow-up was 2 years (range, 1-4 years).

Nine cancers were detected in seven of the 86 women (8.1%) who underwent screening MRI (five invasive ductal carcinomas, one invasive lobular carcinoma, and three ductal carcinoma in situ [DCIS]). Of these nine cancers, five (55%) were found by MRI but not by mammography, three (33%) were found by both modalities, and both mammography and MRI missed one cancer (11%) 1mm in size that was found by mastectomy. Mammography alone did not detect any of these cancers.

Of the nine tumors, eight were found by MRI, for a sensitivity of 89%. Mean size of the cancers was 10.4 mm (range, 1 mm to 25 mm).

“MRI identified the majority of cancers, while mammography picked up only three of nine. For five of the eight MRI-detected cancers, the mammogram from 6 months earlier was normal or showed benign findings. The global picture is that MRI can pick up breast cancers that mammography cannot,” Dr. Le-Petross said. Future studies are needed to confirm these findings.

Longer follow-up will be needed to determine whether earlier detection with an alternative imaging strategy will be life-saving. “We are challenging the gold standard — mammography,” she said.