Tuesday, April 1, 2014
The new uncertainty about mammograms
“I’d like to be tested for every kind of cancer.”
All primary care doctors have heard this request. Our answer is an explanation that we can’t. Understanding this explanation is important before we get to the most recent study about mammograms.
We don’t test for all kinds of cancers for an important reason. The outcome of most cancers don’t depend on when they are diagnosed. This may come as a surprise to many, since we’ve all heard the message of the importance of early diagnosis. But that message only applies to a handful of cancers. Diagnosing colon cancer early definitely saves lives, hence the value of screening colonoscopies. Early diagnosis of cervical cancer is also beneficial, hence Pap tests. But many cancers do not fit this pattern. Take leukemia for instance. Some leukemias are curable; others are not. When they’re diagnosed makes little difference. So testing everyone for leukemia wouldn’t save any lives.
This problem is compounded in cancers that are very-slow growing and occur mostly in older people. These cancers, if undetected, may never harm the patient, and the patient could live a normal lifespan and die of an entirely unrelated problem. Detecting these cancers early doesn’t help anyone. That’s called over-diagnosis, diagnosing a disease that would have never caused harm. (That’s a major problem with prostate cancer screening and is why PSA tests are no longer recommended.)
As of 2009 the best evidence we had suggested that mammograms save lives by diagnosing breast cancer early. (I reviewed the evidence in a post back then.) The U.S. Preventive Services Task Force (USPSTF) combined the data of all the randomized studies of mammograms and calculated that on average 1 life is saved from breast cancer for every 377 women in their 60s who undergo mammograms. For women in their 50s the benefit is smaller (i.e. more women must have mammograms to save one life) and for women in their 40s the benefit is smaller still. Because of the very small benefit to women in their 40s the USPSTF recommended against routine mammograms in this age range. (I disagreed in my post.) And they recommended mammograms every 2 years for women between the ages of 50 and 74.
BMJ published an important study that shines new light on the question. The study began in 1980 and randomized almost 90,000 women in Canada between the ages of 40 and 59 into 2 groups. One group received annual mammograms for 5 years, and the other (the control group) did not. If early detection by mammography saved lives, you would expect more deaths from breast cancer in the control group than in the mammogram group. The initial results, which were published long ago, showed the same number of breast cancer deaths in both groups. The objection was that since breast cancer can grow very slowly a benefit of mammography may not be noticed for many years.
The current study publishes the result of following these women for another 22 years. The results are very surprising. About 500 women died of breast cancer in both groups. The survival curves of the 2 groups were identical, meaning every year the same number of women died of breast cancer in both groups.
To make matters worse, the study showed definite harms of mammography. 106 more cases of breast cancer were diagnosed in the mammogram group than in the control group. But since the same number of women died in both groups those 106 caners were all cases of over-diagnosis, diagnosis of a cancer that would not have harmed the patient. For every 424 women who underwent mammography, one over-diagnosed cancer was detected, resulting in a biopsy and cancer treatment that did not help the patient.
Unfortunately, and predictably, radiologist groups immediately attacked the study. Had they argued “Please keep getting mammograms, otherwise we won’t have as much work to do,” their objections would have at least made sense. One objection was that in 1980 analog mammogram machines were used, and current digital machines are thought to be superior. But all of the studies showing that mammograms were beneficial were done in the 60s and 70s with even older equipment. So to claim that mammograms are proven life-savers and that this study should be ignored because it used old technology is purposely misleading. The current digital technology has never been proven in randomized trials to save lives.
The other objection claimed some methodological flaws. These charges have been denied by the authors of the study and investigated by Canada’s National Cancer Institute, which found no serious flaws. I’ll spare you the technical details. I’m no expert, but I read the study myself and the biggest methodological flaw I found is that BMJ spells “randomized” with an s.
So where does that leave us?
First, we have to remember that this study included women only up to the age of 59. So this study doesn’t tell us anything about the benefit of mammography in women in their 60s or 70s.
But the bigger point is not likely to be refuted that mammograms in women in their 40s and 50s have very small or non-existent benefits and also definite harms. I might not change my current recommendations until groups like the USPSTF mull over the current findings and make new pronouncements, but I will certainly caution women that the benefit of mammograms is controversial and that an abnormal finding could lead to invasive procedures that may not extend their lives.
Vast Study Casts Doubts on Value of Mammograms (New York Times)
Mammograms May Be Useless, Study Finds (Wall Street Journal video)
Cancer screening expert to radiologists: Stop lying about mammograms (Los Angeles Times)
Mammograms: Are they needed or not? (CNN Health)
Mammography Screening (The Medical Letter blog)
Twenty five year follow-up for breast cancer incidence and mortality of the Canadian National Breast Screening Study: randomised screening trial (BMJ article)
New Mammogram Recommendations Betray Women, Doctors and Science (my post in 2009 reviewing the evidence on mammography)
Albert Fuchs, MD, FACP, graduated from the University of California, Los Angeles School of Medicine, where he also did his internal medicine training. Certified by the American Board of Internal Medicine, Dr. Fuchs spent three years as a full-time faculty member at UCLA School of Medicine before opening his private practice in Beverly Hills in 2000. Holding privileges at Cedars-Sinai Medical Center, he is also an assistant clinical professor at UCLA's Department of Medicine. This post originally appeared at his blog.
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Members of the American College of Physicians contribute posts from their own sites to ACP Internistand ACP Hospitalist. Contributors include:
Albert Fuchs, MD, FACP, graduated from the University of California, Los Angeles School of Medicine, where he also did his internal medicine training. Certified by the American Board of Internal Medicine, Dr. Fuchs spent three years as a full-time faculty member at UCLA School of Medicine before opening his private practice in Beverly Hills in 2000.
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Amanda Xi, ACP Medical Student Member, is a first-year medical student at the OUWB School of Medicine, charter class of 2015, in Rochester, Mich., from which she which chronicles her journey through medical training from day 1 of medical school.
Ira S. Nash, MD, FACP, is the senior vice president and executive director of the North Shore-LIJ Medical Group, and a professor of Cardiology and Population Health at Hofstra North Shore-LIJ School of Medicine. He is Board Certified in Internal Medicine and Cardiovascular Diseases and was in the private practice of cardiology before joining the full-time faculty of Massachusetts General Hospital.
Zackary Berger, MD, ACP Member, is a primary care doctor and general internist in the Division of General Internal Medicine at Johns Hopkins. His research interests include doctor-patient communication, bioethics, and systematic reviews.
Controversies in Hospital
Run by three ACP Fellows, this blog ponders vexing issues in infection prevention and control, inside and outside the hospital. Daniel J Diekema, MD, FACP, practices infectious diseases, clinical microbiology, and hospital epidemiology in Iowa City, Iowa, splitting time between seeing patients with infectious diseases, diagnosing infections in the microbiology laboratory, and trying to prevent infections in the hospital. Michael B. Edmond, MD, FACP, is a hospital epidemiologist in Iowa City, IA, with a focus on understanding why infections occur in the hospital and ways to prevent these infections, and sees patients in the inpatient and outpatient settings. Eli N. Perencevich, MD, ACP Member, is an infectious disease physician and epidemiologist in Iowa City, Iowa, who studies methods to halt the spread of resistant bacteria in our hospitals (including novel ways to get everyone to wash their hands).
db's Medical Rants
Robert M. Centor, MD, FACP, contributes short essays contemplating medicine and the health care system.
Suneel Dhand, MD, ACP Member
Suneel Dhand, MD, ACP Member, is a practicing physician in Massachusetts. He has published numerous articles in clinical medicine, covering a wide range of specialty areas including; pulmonology, cardiology, endocrinology, hematology, and infectious disease. He has also authored chapters in the prestigious "5-Minute Clinical Consult" medical textbook. His other clinical interests include quality improvement, hospital safety, hospital utilization, and the use of technology in health care.
Juliet K. Mavromatis, MD, FACP, provides a conversation about health topics for patients and health professionals.
Dr. Mintz' Blog
Matthew Mintz, MD, FACP, has practiced internal medicine for more than a decade and is an Associate Professor of Medicine at an academic medical center on the East Coast. His time is split between teaching medical students and residents, and caring for patients.
Toni Brayer, MD, FACP, blogs about the rapid changes in science, medicine, health and healing in the 21st century.
Vineet Arora, MD, FACP, is Associate Program Director for the Internal Medicine Residency and Assistant Dean of Scholarship & Discovery at the Pritzker School of Medicine for the University of Chicago. Her education and research focus is on resident duty hours, patient handoffs, medical professionalism, and quality of hospital care. She is also an academic hospitalist.
John H. Schumann, MD, FACP, provides transparency on the workings of medical practice and the complexities of hospital care, illuminates the emotional and cognitive aspects of caregiving and decision-making from the perspective of an active primary care physician, and offers behind-the-scenes portraits of hospital sanctums and the people who inhabit them.
Ryan Madanick, MD, ACP Member, is a gastroenterologist at the University of North Carolina School of Medicine, and the Program Director for the GI & Hepatology Fellowship Program. He specializes in diseases of the esophagus, with a strong interest in the diagnosis and treatment of patients who have difficult-to-manage esophageal problems such as refractory GERD, heartburn, and chest pain.
Mike Aref, MD, PhD, FACP, is an academic hospitalist with an interest in basic and clinical science and education, with interests in noninvasive monitoring and diagnostic testing using novel bedside imaging modalities, diagnostic reasoning, medical informatics, new medical education modalities, pre-code/code management, palliative care, patient-physician communication, quality improvement, and quantitative biomedical imaging.
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David Katz, MD
David L. Katz, MD, MPH, FACP, is an internationally renowned authority on nutrition, weight management, and the prevention of chronic disease, and an internationally recognized leader in integrative medicine and patient-centered care.
Richard Just, MD, ACP Member, has 36 years in clinical practice of hematology and medical oncology. His blog is a joint publication with Gregg Masters, MPH.
Kevin Pho, MD, ACP Member, offers one of the Web's definitive sites for influential health commentary.
Michael Kirsch, MD, FACP, addresses the joys and challenges of medical practice, including controversies in the doctor-patient relationship, medical ethics and measuring medical quality. When he's not writing, he's performing colonoscopies.
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Alexander M. Djuricich, MD, FACP, is the Associate Dean for Continuing Medical Education (CME), and a Program Director in Medicine-Pediatrics at the Indiana University School of Medicine in Indianapolis, where he blogs about medical education.
Rob Lamberts, MD, ACP Member, a med-peds and general practice internist, returns with "volume 2" of his personal musings about medicine, life, armadillos and Sasquatch at More Musings (of a Distractible Kind).
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Other blogs of note:
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Also known as the Green Journal, the American Journal of Medicine publishes original clinical articles of interest to physicians in internal medicine and its subspecialities, both in academia and community-based practice.
A collaborative medical blog started by Neil Shapiro, MD, ACP Member, associate program director at New York University Medical Center's internal medicine residency program. Faculty, residents and students contribute case studies, mystery quizzes, news, commentary and more.
Michael Benjamin, MD, ACP member, doesn't accept industry money so he can create an independent, clinician-reviewed space on the Internet for physicians to report and comment on the medical news of the day.
The Public Library of Science's open access materials include a blog.
One of the most popular anonymous blogs written by an emergency room physician.