Radiology: MR + mammo best for women with rad therapy history
 | |
| Breast MRI Navigation software Image source: Sentinelle Medical |
Women who receive radiation therapy as children and young adults for diseases like Hodgkin’s lymphoma face a significantly greater risk of breast cancer later in life with the incidence of breast cancer increasing approximately eight years after chest irradiation. Thirteen to 20 percent of women treated with moderate- to high-dose chest irradiation for a pediatric cancer will be diagnosed with breast cancer by age 40 to 45, which is similar to incidence among women with a BRCA gene mutation.
The American Cancer Society, American College of Radiology, Society of Breast Imaging and the Children’s Oncology Group recommend annual MR screening as an adjunct to mammography for women who face a 20 percent or greater lifetime risk for cancer, including those with a history of radiation therapy to the chest.
The current study sought “to assess the utility of screening MRI in detecting otherwise occult breast cancers in women with a history of radiation therapy to the chest,” explained the study’s lead author Janice S. Sung, MD, radiologist at Memorial Sloan-Kettering Cancer Center (MSKCC) in New York City.
Sung and colleagues reviewed screening breast MRIs performed at MSKCC between January 1999 and December 2008 on women with a history of chest irradiation. They looked at data from 247 screening breast MRIs in 91 women, with a focus on the number of cancers diagnosed, the method of detection and the tumor characteristics.
Of the 10 cancers found during the study period, four were detected with MRI alone, three with MRI and mammography and three with mammography alone. The four cancers detected with MRI alone were invasive, while the three cancers detected with mammography alone were in their early stages.
“These results support existing evidence that MR imaging is more sensitive than mammography in detecting early invasive breast cancers in women who are at high risk due to a genetic mutation or strong family history,” observed the researchers. In contrast, mammography may better depict DCIS [ductal carcinoma in situ], which also reinforces findings from other studies of high-risk populations.
The addition of MRI to the screening process resulted in a 4.4 percent incremental cancer detection rate, which is within the 2 to 7 percent prevalence of cancer detected only at MR imaging reported in other high-risk populations, according to Sung and colleagues. A combination of MRI and mammography produced the highest sensitivity for detecting breast cancers.
However, Sung and colleagues noted that MR studies prompted biopsy recommendations in 24 percent of the cohort, which is relatively high for high-risk MR screening. The biopsy positive predictive value was 29 percent.
Sung and colleagues acknowledged several limitations to the study including a small sample size and variation in the number and timing of screening studies. They also pointed out that “radiation therapy for early Hodgkin’s lymphoma has evolved and current therapy employs a combination of smaller radiation fields and lower radiation doses.” These changes may impact future breast cancer incidence in this population. Another consideration, offered the authors, is that “it is unclear whether [supplemental MR screening] will result in reduced morbidity and mortality within this population.”
“Our results support existing recommendations for annual screening MRI as an adjunct to annual mammography in women with a history of chest irradiation,” Sung et al concluded, while cautioning that “MR imaging should be used in addition to and not in place of mammography in this population, as the sensitivity for detecting breast cancers by using a combination of MR imaging and mammography was higher than that for either modality alone.”