MRI Plus Mammography Finds More Cancers After Chest Irradiation

An MRI scan in addition to mammography detects more breast cancers in women who underwent therapeutic chest radiation as children or young adults, than either modality alone, according a new study released this week in Radiology.

Lead author Janice S. Sung, MD, a radiologist at Memorial Sloan-Kettering Cancer Center in New York City, said that MRI as an adjunct to mammography has already been shown effective at breast cancer screening in women with high risk factors, like family history or genetic mutation. However, this study focused specifically on the risk factor of chest irradiation, mostly for Hodgkin’s Disease.

Women who received a moderate to high dose of chest irradiation at a young age, have a 13 to 20 percent chance of developing breast cancer by age 45. In the general population, the cumulative rate of developing breast cancer by that age is only one percent.

For the retrospective study, Sung and the other authors reviewed 10 years of breast cancer MRI screenings, through 2008, from women who had chest irradiation for a primary cancer. Those included 247 screenings from 91 women. The authors looked at the findings and recommendations on each MRI study, plus they reviewed each woman’s most recent mammogram. They studied the pathology reports for the cancers diagnosed, the method of detection and the tumor characteristics.

During the study period, 10 cancers were found. Of those, four were detected by MRI alone, three from mammography alone, and three from the combination of MRI and mammography. The cancers detected by MRI alone were all invasive carcinomas, whereas the tumors found only by mammography manifested as microcalcifications. Two of those three cancers were ductal carcinoma in situ (DCIS), and the third was DCIS with microinvasion. Of the cancers detected using both modalities, mammography detected microcalcifications in all three, while the MRI found two cancers with mass-like enhancements, and one with linear enhancement.

The combination of MRI and mammography resulted in a 4.4 percent incremental cancer detection rate, and the authors conclude that this course of screening produces the highest sensitivity for breast cancer detection.

The findings support existing evidence that MR imaging has a higher sensitivity in detecting invasive cancer, whereas mammography is more sensitive in finding in situ carcinoma. “Our results support existing recommendations for annual screening MRI as an adjunct to annual mammography in women with a history of chest irradiation,” Dr. Sung said in a statement.

In spite of the benefits, study authors note that few 40 to 50 year old women in this high-risk population undergo breast screening MRI. They opine that this is due to limited insurance coverage and lack of awareness of the screening modality benefit.