New Study Calls for Change In Deciding Frequency of Mammograms
Says factors such as breast density and women’s values should be considered
Issued Jointly By California Pacific Medical Center And UCSF
San Francisco, Calif., July 5, 2011 - Mammograms should not be done on a one-size fits all basis, but instead should be personalized based on a woman’s age, the density of her breasts, her family history of breast cancer and a number of other factors including her own values. That’s the conclusion of a new study in the July 5 issue of the Annals of Internal Medicine.
The study is likely to be controversial as it challenges the current guidelines from groups such as the American Cancer Society and the US Preventive Task Force which recommend one frequency – screening every 1 or 2 years – for all women.
No one doubts that mammograms save lives but there is disagreement over when women should begin getting mammograms and how often they should get them: should they be done every two years starting at 50 or every year starting at age 40?
“Most guidelines use age as the determining factor in when, and how often, a woman should get a mammogram,” says Steve Cummings, MD, of the San Francisco Coordinating Center at the California Pacific Medical Center Research Institute – part of the Sutter Health network - and the lead author of the study. “What our study shows is that other factors, particularly breast density, are just as important, if not more so, in helping a woman decide what is most appropriate for her. We show that mammography should be personalized. The best interval for you depends on your age, breast density, and other risk factors for breast cancer.”
Many studies have shown that the denser a woman’s breast on a mammogram, the greater her risk of breast cancer. Low density or fatty breasts means a low risk of breast cancer while high density or less fatty breasts means a higher risk.
Using data from the Breast Cancer Surveillance Consortium and Surveillance Epidemiology and End Results of the National Cancer Institute the researchers developed a model to compare the lifetime costs and health benefits for women who got mammograms every year, every two years, every three to four years, or who never got a mammogram. The women all had different risk factors for breast cancer and the model assumed that they all began as healthy but could subsequently fall into one of six different categories: remain healthy, develop ductal carcinoma in situ (DCIS), develop localized invasive breast cancer, regional invasive breast cancer, distant invasive breast cancer, die from invasive breast cancer, or die from causes other than breast cancer.
The authors used the data to estimate how many extra mammograms over 10 years would be needed to prevent one death from breast cancer in those having mammograms once every three to four years compared to no mammograms, and in those having mammography every two years compared to once every three to four years. They also estimated the costs for each frequency of mammography for each year of quality life gained.
“Our analysis suggests that women with a first-degree relative with breast cancer or with a history of a breast biopsy should have an initial screening mammography at age 40,’’ said study co-author Karla Kerlikowske, MD, MS, an expert in mammography at the University of California, San Francisco.
“For women age 40 to 49 with high breast density and with either a first-degree relative with breast cancer or a prior breast biopsy, the benefits versus harm for performing mammography every two years is similar to screening an average-risk woman in her 50s. This amounts to about 20 percent of women in their 40s. For women age 40 to 49 without these risk factors, it is reasonable to wait until age 50 to start mammography screening.’’
Lead author Dr. John Schousboe of the Park Nicollet Institute and the University of Minnesota in Minneapolis, Minnesota, noted that yearly mammography was not cost-effective in that it was expensive and yielded little additional health benefits compared to mammography once every 2 years, regardless of breast density or other risk factors.
The frequency of mammography is not just a clinical decision, he said, it also has a strong emotional component. “Feelings matter too. For example some mammograms produce a ‘false positive’ result and these can cause a lot of worry for a woman. The effect of mammograms on a woman’s quality of life should be considered in her decision about when to be screened. If mammograms reassure you, then more often is ok. If they worry or bother you, then less frequent may be ok."
Dr. Susan Love, President of the Dr. Susan Love Research Foundation commented that "this is exactly the type of analysis that we need if we are going to help women and doctors figure out the best schedule of screening for them. Personalized medicine extends beyond treatment to risk definition and appropriate screening schedules. "
The study was supported by grants from Eli Lilly and Co. and the Da Costa Family Foundation for Research in Breast Cancer Prevention at CPMC. However, the sponsors had no role in the design, data collection, analysis or interpretation of the study.
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