Oy! (Probably not the best word to start my website this week, but I couldn’t come up with a different one.) Right after I wrote about the recommendations for women who were found to have dense breasts during their screening mammogram, I, and everyone in the media, read the article published in last week’s JAMA titled ” A Systemic Assessment of Benefits and Risks to Guide Breast Cancer Screening Decisions”.
The authors, who are on the faculties of Brigham and Women’s Hospital and Harvard Medical School, reviewed articles that were published between 1960 and 2014. They searched for information on the benefits of mammogram, harms of mammogram and modes of individualized mammography screening decisions including communication of risks and benefits. The article is long and the citations many, but basically, the conclusion is that there was an overall 15 to 20% decrease in the relative risk of breast cancer-specific mortality as a result of mammography screening. Broken down by age groups, mammography screening was associated with a 15% decrease in breast cancer mortality for women in their 40s and 32% for women in their 60s.
So that’s the good news. The bad news is (according to the article) that the risk of a false positive diagnosis was high… For a 40- or 50- year old woman undergoing 10 years of annual mammograms, the risk of false positive results over that period of time was about 61% and for women aged 66 to 74 who had annual mammograms over 10 years, the false-positive rate was 49.7%. (A false positive result raises suspicion for breast cancer and leads to further testing, additional imaging and/or biopsy but does not result in a cancer diagnosis.) The authors also considered the statistics from published trials on overdiagnosis. (I know this term is difficult to understand when we are discussing breast cancer but basically it means that the type of tumor that was detected, such as DCIS, will not eventually lead to invasive or life-threatening disease and/or the patient will die of something else and not from her breast tumor.)
In order to better convey the context of these statistics, the authors discuss lifetime risk of breast cancer as well as risk at any age. For a woman in United States, the average lifetime risk of breast cancer is 12.3%. However, the 10 year risk of invasive breast cancer at age 40 is “only” 1.5%, at age 50, it’s 2.2% and at age 60 it is 3.5%. (These numbers may somewhat decrease the concerns for many of us who worry about our breast health risk in the decade to come.) The high 12.3% number represents a risk over an entire lifetime… well into our late 80s or even early 90s.
So how do we look at risk-benefit when it comes to screening mammogram? If dollar cost is the issue, it accounts for almost $8 billion in annual health care expenditures in United States. But for those women whose lives have been saved or who had to undergo lesser procedures in order to treat their breast cancer, national cost is probably not an issue. Therapies have improved and most women diagnosed with breast cancer do not die from the disease, even if their tumors were detected without mammography. However, as pointed out in an editorial in the same JAMA issue “many women diagnosed with late stage disease who were not screened recently wrongly blame themselves, encouraging others not to make the same “mistake”. Others attribute their survival to screening mammogram received even when this is unlikely to be the case.”I hope this doesn’t sound too cavalier. These were statements in the articles and I, like many women and physicians, feel that any deaths from breast cancer are tragic.
So how do you decide if and how often you should get screened? The authors give a a list of pointers that should be considered by each woman when she considers making her mammogram appointment and by her physicians who suggest she get screened, especially at an early, under 50 age.
* Many cancers will be found, but most women diagnosed with breast cancer will survive regardless of whether the cancer was found by a mammogram.
* Some cancers that are found would have never caused problems.
* Often, women are called back for further testing because of an abnormality that is not cancer.
* Mammography decreases the number of women who will die from breast cancer. This benefit is greater for women who are at higher risk for breast cancer based on older age or other risk factors such as family history.
* The number of women whose lives are saved because of mammography varies by age. For every 10,000 women who get regular mammograms for the next 10 years, the number whose lives will be saved because of the mammograms over each age group is approximately
- 5 of 10,000 women aged 40 to 49 years
- 10 of 10,000 women aged 50 to 59 years
- 42 of 10,000 women age 60 to 69 years
* If your breast cancer risk is higher than average, you may benefit more from a mammogram than someone with average risk.
* About half or more of women who have a mammogram yearly for 10 years will have a false positive mammogram and need additional studies. Up to 20% of these women will need a biopsy.
* In some women the mammogram will find an invasive cancer or noninvasive conditions such as DCIS that would never have caused problems. We cannot tell which these are so they will be treated just like other cancers. There is about a 19% chance that the cancer is overdiagnosed and treatment may be unnecessary.
I know this all sounds complicated and makes decisions about screening more difficult. But in the end it really has to do with your values and your personal philosophies regarding healthcare. Do you prefer to do more to insure that a diagnosis of this malignancy be made or do you think less is more and want minimize the risk of a false positive result that could cause anxiety, procedures and cost? I prefer the former but realize that many women don’t.