This week the Journal of the American Medical Association (JAMA) published yet another article on mammography and breast cancer screening.
The new report comes from Drs. Lydia Pace and Nancy Keating, both physicians with public health degrees and appointments at Harvard-affiliated institutions. The article has value, and I would find it hard to argue with most of the authors' findings and conclusions.
But already it has generated a predictable round of headlines along the lines of "Large Study Finds Little Benefit in Mammography." Although you might be tiring of the topic, this matters a lot, not just to your author, but to the millions of women who don't want to die prematurely from breast cancer or find themselves with advanced disease. Instead of stamping out breast cancer, it seems like we're just pacing back and forth over the same old data.
Now, a reader might wonder why I remain convinced that mammography -- when done right -- has the potential to save many women's lives and, what's more, spare even greater numbers from the physical, financial and emotional toll of prolonged treatment for Stage 4 disease.
Some of my reasons include the following:
1. Clinical trials, most notably the Swedish trial, have demonstrated a significant survival benefit over the long term. These findings, which demonstrated an advantage or women screened in their 40s, received little attention in the news.
2. Mammography is not all the same. The results depend on the radiologists who interpret the images. Some radiologists, by their training and expertise, deliver lower false positive rates and higher true positive (malignant) "pickup" rates. To say that mammography doesn't work, based on studies over a population, discounts the potential (and likely) benefit of having the procedure done by experts.
3. Pathology methods have improved over the past three decades. Some doctors, including epidemiologists and PCPs, may not be aware of new tools for evaluating tumors that lessen the risk of over-treating early-stage and indolent tumors.
4. Longer survival is not the only benefit of mammography. Late detection involves risks, and costs. "Screening neglect," as some researchers call it, adds intensity to needed treatment when patients first seek care for advanced disease.
Reading the new JAMA paper, "A Systematic Assessment of Benefits and Risks to Guide Breast Cancer Screening Decisions," feels like listening to a well-prepared talk, replete with charts. Essentially, it's a review of large published studies on mammography. The authors examined the literature, going back to 1960 -- but with an appropriate emphasis on more recent studies, to address four (huge, complex) questions: 1) what is the benefit of mammography screening, and how does it vary by patient age and risk?; 2) what are the harms of mammography screening?; 3) what is known about personalizing screening recommendations? 4) how can patients be supported to make more informed decisions about screening?
This is an ambitious set of questions, to say the least. The tables provided, which are for the most part inconclusive, draw heavily on findings that vary in the era of data collected, methods of analysis, and reasonableness of authors' assumptions, i.e. validity.
But there is no news here on mammography, except that these two thoughtful investigators carefully reviewed the literature. There is no new information about mammography's effectiveness, the false positive rate, the harms of screening, over-diagnosis, etc.
Unfortunately the article, at a glance, may add to the growing perception among journalists, primary care physicians who may not read below the paper's title, and others -- including many ordinary women -- that mammography's effectiveness has been, again, disproved. And so if journalists cover this "story," as they have and will, our collective memory will incorrectly recall another negative finding, which this is not.
The authors' main conclusions are that decision aides may be helpful, and that developing better ways of screening for breast cancer would be even better than that. I agree.
(This blog is adapted from a recent post at Medical Lessons.)