June 18, 2014
News Review From Harvard Medical School -- 2 Breast-Cancer Tests for High-Risk Women?
A study of women with a high risk of developing breast cancer has found that annual MRI scans find more cancers than mammograms. The study included 2,207 women, ages 30 to 69. All were at high risk of breast cancer. They had high-risk genes, a family history of breast cancer, a history of radiation treatment before age 30 or other factors that increased breast-cancer risk. All were screened with digital mammograms and breast MRI scans. In the first year, the screening found 35 breast cancers. Of those, 23 were detected by MRI alone and 12 were found on both tests. No cancers were detected by mammogram alone. A researcher, quoted by HealthDay news, said the findings suggest that high-risk women should have both tests each year, starting at age 30. But the testing program will continue, and researchers will report later on long-term results. The Journal of Clinical Oncology published the study online. HealthDay News wrote about it June 17.
By Howard LeWine, M.D.
Harvard Medical School
What Is the Doctor's Reaction?
Angelina Jolie went public with her personal decision to have a double mastectomy. For women like her, at high risk of breast cancer, this choice offers the best prevention. However, most women at high risk make different choices.
High-risk women more often choose screening methods to detect early breast cancer. The international screening guidelines for high-risk women recommend yearly MRI exams starting no later than age 30. This may or may not include yearly mammograms. These guidelines were developed by the American Cancer Society and the United Kingdom Health Service.
MRI uses magnetic fields rather than radiation to create an image of the breast. MRI images provide more detail than mammograms. They detect small cancers that mammograms can miss.
The superiority of MRI screening for women with a high risk of breast cancer is not in question. But mammograms expose women to radiation. Are there benefits to having a mammogram that outweigh the admittedly small risk from radiation? That is, do they detect cancers that MRI exams don't find?
This report helps answer that question for now. In Canada, the Ontario Breast Screening Program includes both yearly MRI and mammograms in its screening for high-risk women. Women ages 30 to 69 are eligible for the program.
MRI detected all of the breast cancers confirmed by biopsy. However, 23 of 35 breast cancers seen on MRI were not found on mammograms. So clearly breast MRI for high-risk women is warranted.
What might adding a mammogram to an MRI offer these women? In this study and other studies, breast MRI showed many more false positives than mammograms. False positives are spots that could be cancers. But on further testing, usually biopsy, they are not found to be cancers. Mammograms also can show false positives, but not as often. So perhaps a woman who had a questionable MRI might be spared a biopsy or surgery if her mammogram appeared normal.
What Changes Can I Make Now?
You are at high risk of breast cancer if you have a 20% or greater lifetime risk of developing it. Experts generally use the following standards to determine which women belong in that high-risk category:
- A known genetic risk, as determined by a positive test for mutations in the BRCA1 or BRCA2 genes. The estimated lifetime risk for these women is 40% to 87%.
- Other strong breast-cancer risk genes or, if you have not been tested, a first-degree relative (parent, sibling or child) who has tested positive for these gene mutations.
- A lifetime risk of 20% to 25%, as calculated by tools developed by the National Cancer Institute (NCI) and other organizations. You can find the NCI risk calculator at www.cancer.gov/bcrisktool.
- Radiation therapy delivered to the chest between the ages of 10 and 30. Regular screening is particularly important for survivors of Hodgkin's disease. They have nearly a 50% risk of developing breast cancer.
- A family cancer syndrome or certain other rare genetic disorders. These conditions may increase breast-cancer risk by causing mutations in genes that suppress tumor growth or cause chromosome damage.
If you are at high risk of breast cancer, you should have breast MRI yearly. You and your doctor can decide if a yearly mammogram is also needed.
If you're uncertain about your risk, talk with your doctor. Your risk for breast cancer changes with age and family history. Be sure to update your doctor if new cases of cancer occur in your family. Your doctor may refer you to a genetics counselor for a detailed assessment.
What Can I Expect Looking to the Future?
The Ontario Breast Cancer Program will continue to offer both MRI and mammograms each year to women at high breast-cancer risk. Future reports on their findings will help determine which women might need only MRI exams and which women would benefit from getting both.