The Never Ending Controversy of Screening Mammography
Well, it seems like this topic is like a cat, having multiple (probably more than nine) lives. I posted about mammograms, and, the ongoing ‘controversy’ in February, 2014, and, the topic constantly resurfaces: Are mammograms necessary? Are they ‘harmful’? When should we start? Who should have one and how often?
Truths are truths … no one can disagree.
Mammography screening is one of the major medical advances in the last 50 years. However, it has undergone greater scrutiny and more challenges than virtually any other medical intervention. – Daniel B. Kopans, MD (Miami Breast Conference, 2015)
Facts About Screening Mammography:
1. Randomized, controlled trials have, unequivocally, shown a statistically significant mortality reduction for screening mammogrpahy beginning at the age of 40 years.
2. When mammography screening is introduced into general populations, the death rate from breast cancer declines.
3. Randomized, controlled trials have shown a benefit from mammography screening women ages 40-49 years.
4. Since 1990 (approximately 5 years after screening mammography became ‘standard’; and, enough time to identify mortality differences), the breast cancer death rate per 100,000 females began to fall; over the same period, with access to the same therapy, the death rate for MEN ultimately remained the same. Why? WOMEN ARE BEING SCREENED!
5. Screening mammography does not prevent breast cancer.
6. Screening mammography is not perfect.
So, why the controversy?
Some of the fiction …
1. The radiation from the mammogram will cause more cancers than will be cured – FACT: radiation risk is age related and decreases to unmeasurable levels by age 40.
2. There is no benefit from screening women ages 40-49 – FACT: the randomized controlled trials have always shown a significant reduction for screening women ages 40-49. Flawed analyses created a false impression. With longer follow-up the benefit is significant.
3. The parameters of screening change abruptly at the age of 50 – FACT: age 50 was made to look like a threshold by grouping and averaging data. None of the parameters of screening changes at 50 or any other age. The recall rate from screening AND the percentage of women who are recommended for biopsy is constant with no abrupt change at age 50 or any other age.
4. Breast cancer is not a big issue for women ages 40-49 years – FACT: more than 30,000 women are diagnosed with breast cancer each year while in their forties. More than 40% of the years of life lost are due to breast cancers among women in their forties.
5. Mammography screening leads to false positive studies that lead to biopsies that permanently scar the breast so that when a lesion is palpable the mammogram is useless – FACT: most ‘false positive studies’ are resolved by a few extra pictures or an ultrasound; a ‘benign’ biopsy heals with little or no residual changes on the mammogram; once a lesion is palpable most of the value of the mammogram has been lost.
6. The breast tissues are dense prior to the age of 50 hiding most cancers. At age 50 the breasts turn to fat and screening begins to save lives – FACT: the percent of women with dense breasts declines gradually with age, with no sudden drop at ANY age. 50% of women over the age of 50 have “dense” tissue.
7. Screening women in their forties should be based on their risk of developing breast cancer – FACT: women with a genetic predisposition (BRCA 1 or 2) account for only 10% of cancers each year while other risk factors account for another 15%. THE VAST MAJORITY OF WOMEN WITH BREAST CANCER (75%) HAVE NO IDENTIFIABLE RISK FACTORS. If only high risk women are screened most women who develop breast cancer will not benefit from early detection.
8. Money can be saved by allowing women to die from breast cancer by starting screening at age 50 and screening every two years (this is the current US Preventative Task Force recommendation) – FACT: dying from breast cancer is expensive. $250,000 for the last year of life and another $250,000 in economic and societal losses (this increases to $1.4 million for women who die in their forties).
The “debate” is not about the facts, but has been the result of data manipulation, and pseudoscience that has been permitted and perpetuated by bias and failed peer review at the medical journals, and disseminated by an uncritical media. Mammography is not the ultimate answer to breast cancer. It does not find all cancers and does not find all cancers early enough for a cure, but while we wait for a cure, or a safe way to prevent breast cancer, ALL WOMEN 40 AND OVER SHOULD BE ENCOURAGED TO PARTICIPATE IN SCREENING EVERY YEAR.
A recent publication (The Breast Journal, Volume 21 Number 1, 2015; 13-20) analyzed 9 randomized breast cancer screening trials, and, found that in the trials that achieved a 20% or greater reduction in advanced stage disease, there was an average breast cancer mortality reduction of 28% among women invited to screening. It is important to understand, that using advanced disease at diagnosis, as a surrogate for survival, will underestimate the survival advantage, since some women who are diagnosed with ‘early’ stage disease, will unfortunately also suffer mortality, and, some in the advanced stage will survive due to the biology of their disease. This is the motivation for recent legislation in the USA states requiring imaging practices to inform women with significant breast density that they are at higher risk of a missed cancer, and, that they should consider having a discussion on supplemental/additional imaging. Finally, the important role of early detection in reducing the incidence rate of advanced disease has additional benefits beyond a reduction in breast cancer specific mortality, and these benefits often go unmentioned in debates over the value of screening in the era of improved therapy. These advantages include having the option of breast conserving therapy, which in addition to avoiding removal of the entire breast is associated with fewer side effects, postoperative upper body impairments, less chronic pain, less sexual dysfunction, better body image, and, less psychological distress. The option of removing less lymph nodes, is associated with less post operative symptomatology. The need for chemotherapy and radiation therapy are much more likely when treating advanced disease. Thus, early detection is also associated with reduction in the risk of greater treatment morbidity and diminished quality of life after diagnosis.
(Most of this information was presented at the 2015 Miami Breast Cancer Conference by Dr. Daniel B. Kopans, MD; Professor of Radiology; Harvard Medical School; Senior Radiologist Breast Imaging Division; Massachusetts General Hospital)