Do mammograms make sense as an early-warning tool for most seemingly healthy women over age 40? I say yes — with some caveats — to this long and hotly debated question. Others, of course, say no.
Critics of annual mammograms point to the issue of overtreatment. Just last month, for example, a report in the Annals of Internal Medicine showed that screening mammograms (those done for women without signs of breast cancer) often lead to unnecessary treatments. One in three women in the study whose breast cancer was identified by a screening mammogram had a potentially harmless disease that may not require treatment. That work has raised questions about the benefits of screening mammograms.
The findings of screening studies, including mammography, can be influenced by certain biases in the study design.
Length-time bias means that screening is more likely to identify relatively slow-growing cancers which pose less risk to life than more aggressive cancers. This was at play in the Annals study. Lead-time bias means that patients diagnosed through screening, before disease symptoms appear, appear to live longer.
Such biases can come into play in cohort studies, like the Annals report, which follow a large group of women, some of whom chose to have mammograms and others who didn’t. Length-time and lead-time biases can be minimized by randomized clinical trials, in which a large number of women are enrolled. Half of the participants are randomly selected to have screening mammograms, and the other half do not have screening mammograms. A number of such trials have been conducted in the United States and around the world.
Analyses of completed randomized trials have clearly demonstrated a benefit for screening mammograms, with a 15 to 20 percent reduction in breast cancer deaths.
That said, concerns about overtreatment after a suspicious mammogram are valid. The best way to avoid overtreatment of less-aggressive breast cancers is to more accurately characterize the biologic type of every breast cancer. This approach is leading to more appropriate treatment.
For example, we know that breast-conserving surgery (lumpectomy) is just as effective as mastectomy for most women with breast cancer. And recent studies have confirmed that many women with ductal carcinoma in situ, a type of cancer in which the cancerous cells are confined to the lining of the milk ducts and haven’t spread beyond them, do not require radiation after surgery because this type of cancer isn’t very aggressive and poses little risk.
Based on genomic testing studies, we know that there are different molecular subtypes of cancer. One woman’s breast cancer may be quite different from another’s; each type has its own prognosis and requires its own medical treatment.
Many cases of invasive breast cancer are less biologically aggressive than others. The groundbreaking MINDACT study of nearly 6,700 European women with breast cancer showed that genomic testing allowed nearly half of those diagnosed with early-stage invasive breast cancer to safely avoid chemotherapy without compromising their chance of a cure.
Some guidelines recommend that women begin having regular mammograms at age 40, others recommend starting at age 50. Which one is “right” is more an issue about population health than individual health. Adopting what I call “smart screening” may be a better approach. It involves earlier and possibly more intense breast cancer screening among women at higher risk for the disease, perhaps because of their family history, and later and possibly less-intense screening among those at low risk.
When breast cancer is detected, a complete diagnosis must include a review of the cancer’s biology. To make that happen, women diagnosed with breast cancer should see both an oncologist and a surgeon and have their cancer’s genome sequenced before starting any treatment. More than ever, women should feel empowered to take an active role in their treatment by educating themselves, asking questions, and seeking additional medical opinions until they feel comfortable with their path forward.
Treatment options for breast cancer treatment were once determined by the stage of the disease. Today, one-size-fits-all treatment for a particular cancer stage doesn’t work — treatment should be determined first by testing the cancer’s genome to identify its biologic type then by determining the stage of the disease and how much cancer is present.
By combining all of this information, women with early stage breast cancer can get the right treatment and most can confidently expect to be cured of their disease.
Dennis Citrin, MD, is a board-certified medical oncologist at Cancer Treatment Centers of America at Midwestern Regional Medical Center and the author of Knowledge Is Power: What Every Woman Should Know About Breast Cancer.
As soon as you start talking about relative reductions in incidence of the disease without mentioning absolute rates of all cause mortality, and rates of unnecessary morbidity you lose me. Sorry. Not convinced- look beyond disease specific death rates and you see pretty much an ineffective screening program, and at worst, a net harm.
This article wasn’t fact checked and is misleading and makes me question the credibility of Stat. This is not rocket science and a 2 minute google search would give you multiple articles in the last 2 years that disprove any claim that breast cancer screening prevents deaths.
Your link goes to an outdated 2002 article.
1) There is NO evidence that screening prevents deaths based on meta-analysis, and huge studies in europe.
“A new UK study suggests screening for breast cancer does not reduce deaths from the disease. The study, which looked at nearly 40 years of breast screening, adds to the controversy surrounding whether it is screening or improvement in treatment that accounts for the fall in rates of death from breast cancer.
The researchers from the Department of Public Health at the University of Oxford, report their findings online in the June issue of the Journal of the Royal Society of Medicine.”
2) Another study
“The Canadian study tracked almost 90,000 women for 25 years, and found that having an annual mammogram between the ages of 40 to 59 did not lower the chance of dying from breast cancer more than having a physical examination. ”
3) Finally just last year, a new study in the New England Journal of Medicine “After more than 30 years of widespread promotion of routine breast cancer screening for women at average risk, an undeniable body of research shows the significant harms and limited benefits of population-based screening. The truth is that widespread mammography screening has failed to dramatically reduce the number of deaths from breast cancer. “four out of five (81%) of the tumors actually represented overdiagnosis, or a diagnosis of breast cancer that would never cause symptoms or lead to death.”
Hello, The studies you referenced are not new studies but a re-evaluation of the same older studies. And the reason is simple, all of the randomized clinical trials of screening mammography in large populations were initiated decades ago.
1. The “new UK study” published in the Journal of The Royal Society of Medicine is not in fact, a new study but is a re-calculation of the original Swedish five county study published in 2002.
The authors concluded that based on statistical methodology, the reported reduction in mortality (20%) associated with mammographic screening was too high. However, their re-calculation still showed a significant reduction in breast cancer deaths in the screened population compared with unscreened.
To quote directly from the paper:
“So, proper allocation of breast cancer deaths to the intervention and post-intervention periods led to an equalization of relative risks found for the intervention, post-intervention and follow-up periods, with a risk of breast cancer death that remained about 15% lower in the screening group throughout the entire trial duration.”
For those who wish to read the entire paper, see:
2. The Canadian study (which is also 25 years old) has been criticized by numerous authors for its quality, randomization, and design. A recent review of these criticisms (Heywang-Kobrunner et al in European Radiology vol 26 pp 342-350, Feb 2016) concluded:
“Twenty-five-year follow-up data of the Canadian National Breast Cancer Screening Study (CNBSS) indicated no mortality reduction. What conclusions should be drawn? After conducting a systematic literature search and narrative analysis, we wish to recapitulate important details of this study, which may have been neglected: Sixty-eight percent of all included cancers were palpable, a situation that does not allow testing the value of early detection. Randomization was performed at the sites after palpation while blinding was not guaranteed. In the first round, this “randomization” assigned 19/24 late stage cancers to the mammography group and only five to the control group, supporting the suspicion of severe errors in the randomisation process. The responsible physicist rated mammography quality as “far below state of the art of that time. Radiological advisors resigned during the study due to unacceptable image quality, training, and medical quality assurance. Each described problem may strongly influence the results between study and control groups. Twenty-five years of follow-up cannot heal these fundamental problems. This study is inappropriate for evidence-based conclusions. The technology and quality assurance of the diagnostic chain is shown to be contrary to today’s screening programs, and the results of the CNBSS are not applicable to them.
3. The third study she referred to (the 2016 New England Journal paper) does not directly compare death rates in screened and unscreened patients. It does show that screening results in the detection of smaller tumors, and the size of the invasive cancer is clearly recognized to be an important prognostic factor. To quote directly from the paper:
“After the advent of screening mammography, the proportion of detected breast tumors that were small (invasive tumors measuring <2 cm or in situ carcinomas) increased from 36% to 68%; the proportion of detected tumors that were large (invasive tumors measuring ≥2 cm) decreased from 64% to 32%…The potential of screening to lower breast cancer mortality is reflected in the declining incidence of larger tumors. However, with respect to only these large tumors, the decline in the size-specific case fatality rate suggests that improved treatment was responsible for at least two-thirds of the reduction in breast cancer mortality."
The paper concludes that screening mammography results in nearly a doubling of the incidence of small tumors. The authors conclude that approximately two-thirds of the observed reduction breast cancer deaths can be attributed to better treatment, implying that "only one third" are due to screening mammography.
As a practicing medical oncologist who treats women with breast cancer every day, I can assure the reader that the prognosis for patients with smaller tumors is significantly better and the treatment required is also often much less invasive.
A 15 to 20 percent reduction in breast cancer death with zero reduction in all cause mortality. Doesn’t look so good with a broader gaze
Hello Michael, 40,000 women die every year in the United States from breast cancer. A 20% reduction means 8,000 lives saved, over a decade 80,000. Not so insignificant from my perspective!
You did not provide us with your screening preference. Yes, a lot of what you said are truisms: genetic markers help, some study methodology has flaws, the science is imperfect, etc.
But how do you “‘personalize” and based on your conclusions, what percentage of women would you screen at younger ages (40 yo) based on your insights of US population data? I am making the question easier by asking it from population level. A small percentage? If yes, how would you take it to the individual level with precision?
Hi Brad, the preferred method for screening remains mammography and an important point to make is that technology of mammography has undergone major advances in the 30+ years since the screening studies were first evaluated.
Lack of space prevents a detailed discussion here of when the first screening mammogram should be obtained (40 vs. 50), annual vs. biannual. Important to remember that only approximately 10% of women who develop breast cancer have an identifiable familial risk. Every woman has enough of a risk that she should have screening mammograms.
In addition to the 240,000 diagnosed annually with invasive breast cancer, an additional 60,000 are now diagnosed annually with DCIS (ductal carcinoma in situ which is pre-invasive cancer). The increased diagnosis of DCIS over the past thirty years is largely attributable to screening mammogram. Not only is DCIS virtually 100% curable, treatment is much simpler than treatment of invasive breast cancer; no need for chemotherapy.
The most recent review of the subject of screening for breast cancer from the US Preventive Services Task Force (Feb 2016) states: The USPSTF found adequate evidence that mammography screening reduces breast cancer mortality in women aged 40 to 74 years.”
To read the entire report, click on the link below:
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