I’ve written more times than I can remember about the phenomenon of overdiagnosis and the phenomenon that is linked at the hip with it, overtreatment. Overdiagnosis is a problem that arises when large populations of asymptomatic, apparently healthy people are screened for a disease or a condition, the idea being that catching the disease at an earlier stage in its progression will allow for more successful treatment. Two prominent examples include—of course—screening for breast cancer with mammography and screening for prostate cancer with prostate-specific antigen (PSA) testing, and I’ve written about the problem of overdiagnosis with each of them on many occasions. Basically, overdiagnosis occurs when the screening test picks up what we call “preclinical” disease (i.e., disease that hasn’t become symptomatic) that, if left untreated, would never become symptomatic or endanger the health or life of the patient). Although intuitively, it seems to the lay public (and, truth be told, most doctors) that detecting cancer earlier must be inherently better, it turns out that it’s way more complicated than you think. There is a price to be paid for early diagnosis in the form of overtreatment of disease that doesn’t need treatment and for disease that is destined to threaten the life of the patient earlier treatment doesn’t always result in better outcomes. Also, whenever you screen for a condition in asymptomatic people, you will always—always—find much more of it, and the significance of those added diagnoses is not always clear, as a new study in JAMA Oncology shows.
DCIS and mammography: Some background
Before I get to the meat of the study, from my perspective, nowhere is the problem of overdiagnosis and overtreatment in cancer screening as pronounced than in the condition known as ductal carcinoma in situ (DCIS). DCIS is commonly referred to as “stage 0” breast cancer and is characterized by milk duct cells that appear malignant but remain confined to the milk ducts. In other words, they haven’t invaded the tissue surrounding the ducts. In general, DCIS is treated similarly to breast cancer, with surgical excision, either by mastectomy or breast-conserving surgery, followed by radiation therapy if breast conserving surgery is used. Then, depending on its hormone receptor status, adjuvant treatment consists of blocking estrogen for five years. The rationale for this treatment is the view of DCIS as being a precursor to fully invasive breast cancer and that treating the DCIS will prevent the development of breast cancer. Over the last couple of decades, however, it has become clear that not all DCIS is created equal. Much of it will never progress to breast cancer in the lifetime of the woman (particularly if the woman is older, which means less time for fully malignant transformation to occur). Evidence suggesting this includes studies showing an increase in DCIS incidence by 16-fold since the 1970s, when mammography started to be introduced on a large scale, with little change in the incidence of invasive cancer. Today, 20-25% of mammography-detected breast cancer diagnoses are DCIS; forty years ago, DCIS was an uncommon diagnosis, except associated with an invasive cancer.
Blogging is a rather immediate endeavor. Over the last nine years (nearly), I’ve lost track of how many times I saw something that I wanted to blog about but by the time I got around to it, it was no longer topical. Usually what happens is that my Dug the Dog tendencies take over, as I’m distracted by yet another squirrel, although sometimes there are just too many
targets topics and too little time. Fortunately, however, sometimes the issue is resurrected, sometimes in a really dumb way, such that I have an excuse to correct my previous oversight. This is just such a time, and the manner in which the topic has been resurrected is every bit as dumb as the rant by the Food Babe that Mark Crislip so delightfully deconstructed last Friday. Unfortunately, for purposes of snark, I’m not Mark Crislip—but, then, who is?—but fortunately I am known elsewhere (and sometimes here) for being a bit “insolent.” So let’s dig in. We’ll start with the idiocy and then use that as a “teachable moment” about cancer biology. Funny how I manage to do that sort of thing so often.
Abuse of cancer science for political purposes
I realize that we at SBM are supposed to stay, for the most part, apolitical, but the idiocy that’s leading me to revisit a topic is unavoidably political because it involves using a profound misunderstanding of science for political ends. Specifically, I’m referring to the misuse of a legitimate scientific debate about cancer screening and diagnosis for purely political ends. First, however, for those not living in the US or my fellow citizens who might be blissfully unaware (in this case) of recent events, during the first half of October, our nation underwent what can only be described as a self-inflicted crisis that could have caused worldwide economic turmoil if it hadn’t been (sort of) resolved at the last minute. The reason for the crisis boiled down to the extreme resistance of some of our more radically conservative Representatives to the Patient Protection and Affordable Care Act, usually referred to as just the Affordable Care Act (ACA) or, colloquially, Obamacare. Normally when we write about Obamacare here on SBM, it’s to complain about how advocates of unscientific medicine and outright quackery have tried to piggyback their advocacy on the ACA in order to have health insurance plans sold through government exchanges cover modalities like naturopathy, chiropractic, and other so-called “complementary and alternative medicine” (CAM) or “integrative medicine.” In related posts, I’ve examined the evidence with respect to the relationship between health insurance and mortality and whether attacks on Medicaid as not improving the health of patients insured by it have any validity. (Let’s just say they are oversimplifications and distortions.)
There are times when the best-laid blogging plans of mice and men often go awry, and this isn’t always a bad thing. As the day on which so many Americans indulge in mass consumption of tryptophan-laden meat in order to give thanks approached, I had tentatively planned on doing an update on Stanislaw Burzynski, given that he appears to have slithered away from justice yet again. Then what to my wondering eyes should appear in my e-mail in box but news of a study that practically grabbed me by my collars, shook me, and demanded that I blog about it. As if to emphasize the point, suddenly e-mails started appearing by people who had seen stories about the study and, for reasons that I still can’t figure out after all these years, were interested on my take on the study. Yes, I realize that I’m a breast cancer surgeon and therefore considered an expert on the topic of the study, mammography. I also realize that I’ve written about it a few times before. Even so, it never ceases to amaze me, even after all these years, that anyone gives a rodential posterior about what I think. Then I started getting a couple of e-mails from people at work, and I knew that Burzynski had to wait or that he would be relegated to my not-so-secret other blog (I haven’t decided yet).
As is my usual habit, I’ll set the study up by citing how it’s being spun in the press. My local home town paper seems as good a place to begin as any, even though the story was reprinted from USA Today. The title of its coverage was Many women receiving unnecessary breast cancer treatment, study shows, with the article released the day before the study came out in the New England Journal of Medicine: