Breast Cancer Screening and Mammography
On November 22, 2012, the New England Journal of Medicine published the results of a study examining trends in the screening of breast cancer between 1976 and 2008. The researchers found that screening has promoted a two-fold increase in the number of women diagnosed with early stage breast cancer. However, the findings also indicated the number of women diagnosed with late stage cancer has not significantly declined. Thus, the study concludes that many women, as many as 1.3 million over 30 years and 31% of women diagnosed with breast cancer in 2008 alone, were overdiagnosed. Overdiagnosis means that tumors were detected which would not have resulted in clinical symptoms during the woman’s lifetime. The article discussing the study is available to subscribers here.
The recent study would appear to support a decision by the U.S. Preventive Services Task Force (USPSTF) in December 2009 to abandon its earlier recommendation of breast cancer screening every 1 to 2 years for all women over age 40. The USPSTF now recommends clinicians recommend biennial screening for women ages 50 to 74 and “individualize decision making to begin biennial screening according to the patient’s context and values” for women between the ages of 40 and 49. The Task Force reasoned that the benefit of screening before age 50 was small compared with the potential harms of screening , such as psychological harm, unnecessary imaging and biopsies, harm associated with unnecessary treatment, exposure to radiation, and inconvenience related to false-positive findings. Like the NEJM study more recently, the Task Force cited the harm of overdiagnosis prompting women to undergo treatment and possible complications from treatment of an early form of cancer which may never become clinically apparent or cause death.
It is important to understand the USPSTF guidelines do not represent a universal consensus on breast cancer screening. On July 20, 2011, the American College of Obstetricians and Gynecologists (ACOG) recommended annual screening mammography starting at age 40. Critical to this recommendation is data showing the window of opportunity between the time very small evidence of cancer is detectable by mammogram and when that cancer becomes symptomatic is shortest for women between the ages of 40-49 (2 – 2.4 years compared with 4-4.1 years for ages 70-74). Thus, although the incidence of breast cancer in women ages 40-49 is smaller than in older women, annual mammograms improve the chances of detecting and treating cancer in women in their 40’s before the cancer spreads.
To major non-profit organizations involved in the fight against breast cancer recommend screening for women over the age of 40: the American Cancer Society and Susan G. Komen for the Cure recommend annual mammography for women over age 40. In addition, the National Cancer Institute recommends screening mammography every 1-2 years for women over age 40.
The experts do not disagree that breast cancer screening saves lives. The real debate is over screening guidelines that properly weigh the benefits against the perceived harms of early breast cancer screening. The USPSTF acknowledges the sequence by which ductal carcinoma in situ (DCIS), the most prevalent form of early breast cancer, develops into invasive cancer is unknown. And though not all cases of DCIS progress to invasive cancer, the likelihood that DCIS will develop into invasive cancer is unknown.
It should be no surprise Susan G. Komen, ACOG, the American Cancer Society and the National Cancer Institute recommend screening mammography for women after age 40. The USPSTF emphasizes the perceived harms associated with testing and treatment for women who have early forms of cancer that may never shorten their lives. In this writer’s opinion, it’s dangerous to create guidelines for cancer screening which assume women would prefer to wait as many as 10 years before they learn they have breast cancer. People consider cancer a killer who they should not gamble with. Adherence to USPSTF guidelines will allow breast cancer to smolder for years before diagnosis, with no way of knowing whether the delay will prove the difference between life and death for many women.
Recommending against screening mammography before the age of 50 is like assuming women who learn they have early or non-symptomatic breast cancer would take the bet their cancer will remain noninvasive and defer treatment. The lives of women in their 40’s with breast cancer who are not lucky enough to have a slow growing form of the disease should not be cast aside as statistically insignificant.
Risk tolerance varies from individual to individual. But the debate about screening for breast cancer begs the question: how many women would decide the benefit of the early diagnosis outweighs the risk of overdiagnosis? In a study conducted in Pittsburgh, PA, on questioning of over 1500 women between 40 and 59, 97% of women claimed a false-positive result would not deter them from continuing with regular screening and most would be willing to be recalled for non-invasive or invasive testing if it improved their chances of detecting cancer earlier. See Ganott M.A. Screening Mammography: Do Women Prefer a Higher Recall Rate Given the Possibility of Earlier Detection of Cancer? Radiology 238:3, 793-800 (March 2006). Interestingly, an article recently published in the Pittsburgh Post-Gazette discusses a recent study by the Pennsylvania Health Care Cost Containment Council and observations by a local physician and her colleagues of the increasing number of women choosing to undergo preventive mastectomies. Preventive mastectomies may represent only one end of the spectrum, but such a trend underscores how important it is for clinicians to make sure every patient has an opportunity to understand and make informed decisions about breast cancer screening.
It is extremely important that people recognize and understand the debate about screening mammography. Patients and their loved ones must stay informed about their options and the risks. Clinicians must fully inform their patients about the potential harms and benefits of screening before age 50 and at 1 or 2 year intervals. People trust their doctors to use their professional judgment and recommend the best care for a given condition. However, with the varied data and recommendations for breast cancer screening so dependent on the perceived physical and psychological harms of overdiagnosis, it is impossible to exclude the patient and their family from the equation. The true harm associated with screening mammography is measured on a personal level.
From a different perspective, Dr. Andrew Kaunitz offers a concise statement summarizing the recent NEJM study and how clinician could best address the uncertainty regarding which breast cancers will progress to advanced disease – http://www.medscape.com/viewarticle/775209.