Researchers at Princess Margaret Cancer Centre have confirmed in a screening effectiveness study that early screening with magnetic resonance imaging (MRI) can reduce breast cancer mortality for female survivors of childhood Hodgkin lymphoma who received chest radiation.
The findings published by Hodgson et al in the Journal of the National Cancer Institute build on previous clinical work that demonstrated MRI detects breast cancer at early stages in young survivors who are not old enough to start standard breast cancer screening, said David Hodgson, MD, MPH, a radiation oncologist at the Princess Margaret Cancer Centre, University Health Network. Dr. Hodgson is also a Professor in the Department of Radiation Oncology, Faculty of Medicine at the University of Toronto.
“If you are a young woman who was treated with radiation therapy to your chest as a teenager or child for Hodgkin lymphoma, or for that matter, chest radiation therapy for any reason, you should be having a conversation with your family doctor or your oncologist about whether to start breast cancer screening earlier than most women would,” said Dr. Hodgson.
Dr. Hodgson estimates that there are thousands of Hodgkin lymphoma survivors in North America treated throughout the 1990's and later who received chest radiation therapy and are unaware they are at risk and eligible for early screening. “Many of these are women who received radiotherapy to more normal tissue or at higher doses than are used currently, but even for more recently treated patients, screening should reduce the risk of breast cancer death.”
For the study, Dr. Hodgson's research team gathered published information from dozens of studies about the risk of developing breast cancer in childhood lymphoma survivors, the accuracy of different forms of breast cancer screening, and the rates at which women agree to be screened when asked.
Using mathematical models, the researchers used these data to quantify the effectiveness of starting screening early—at age 25—for women who received chest radiation as a teenager. They found that using mammography, about 260 survivors of childhood lymphoma would need to be invited to have early breast cancer screening to prevent one breast cancer death, which compares favorably to widely endorsed screening programs for average risk women aged 50 or older, which generally require 300 to 1,300 women to be invited to prevent one breast cancer death. Notably, the use of MRI for screening improved the effectiveness considerably compared to mammography, reducing the number of women needing screening to prevent one breast cancer death to less than 80.
Dr. Hodgson cautions that “false-positives” from MRI screening are common given that this scanning method is so sensitive it detects many changes in breast tissue, most of which are not cancer. The results indicate that from the age of 25 to 39, about a third of patients will have a false-positive, and as screening extends to age 75, almost 80% of women screened with MRI will have at least one false-positive. “This is important for patients to know and for physicians to counsel patients about because it's stressful for a patient to be called back about suspicious finding,” the researchers concluded.
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