Further adventures in misunderstanding risk

Missing appendicitis can be a death sentence. It’s not a prolonged one, either. If you have appendicitis, you pretty much get treatment (an appendectomy, or at least antibiotics), or it ruptures, you get much, much sicker. At that point, you get treatment, or you die. Treating an already ruptured appendix is much, much harder than treating an unruptured one, with more complications and an increased risk of death.

Because of this, doctors err on the side of caution. We accept that we will take a certain number of people to the operating room to have an appendectomy, and wind up removing a normal appendix. We do this because we’d rather have a certain number of people have an unnecessary procedure than suffer the real and known complications of a burst appendix.

But surgeons still hate that. They don’t want to subject people, including kids, to unnecessary surgery. Even though the rates of normal appendices removed have been, in the last decade, in the 18% range, we keep working on technology to reduce the false positive rate. A more recent study found that the percent of normal appendices removed had dropped to 14%. That’s still not good enough.

I bring this up because “Social and Clinical Determinants of Contralateral Prophylactic Mastectomy” was just published in JAMA Surgery:

Importance: The growing rate of contralateral prophylactic mastectomy (CPM) among women diagnosed as having breast cancer has raised concerns about potential for overtreatment. Yet, there are few large survey studies of factors that affect women’s decisions for this surgical treatment option.

Objective: To determine factors associated with the use of CPM in a population-based sample of patients with breast cancer.

Design, Setting, and Participants: A longitudinal survey of 2290 women newly diagnosed as having breast cancer who reported to the Detroit and Los Angeles Surveillance, Epidemiology, and End Results registries from June 1, 2005, to February 1, 2007, and again 4 years later (June 2009 to February 2010) merged with Surveillance, Epidemiology, and End Results registry data (n = 1536). Multinomial logistic regression was used to evaluate factors associated with type of surgery. Primary independent variables included clinical indications for CPM (genetic mutation and/or strong family history), diagnostic magnetic resonance imaging, and patient extent of worry about recurrence at the time of treatment decision making.

Main Outcomes and Measures: Type of surgery received from patient self-report, categorized as CPM, unilateral mastectomy, or breast conservation surgery.

This was a study looking at women who had breast cancer, and then had to decide whether to remove their other breast “prophylactically”. It’s important to understand that most women don’t need that procedure. The Society of Surgical Oncology says it should only be considered in women who have a genetic mutation, like a BRCA gene mutation, or a family history of at least two first-degree relatives with breast or ovarian cancer.

This study found, however, that 69% of the women who had the procedure performed had neither of these risk factors. A Cochrane Review of the procedure found that it does not improve survival in women without these risk factors. The vast majority of women who underwent a prophylactic mastectomy will receive no benefit from it at all.

It gets worse. Women who had an MRI were significantly more likely to have the procedure, even when the MRI showed nothing was wrong with their other breast. New technology is increasing the rate of unnecessary procedures, not decreasing it.

I started this post with a discussion of appendectomies, because I wanted to show you that we have a reference point. There are other diseases that are life threatening, scary, and can lead to unnecessary procedures. In those instances, we act. We accept a false positive rate, but work to keep it low. Our addition of new technologies tries to reduce that low number even further.

With respect to breast cancer, though, we seem willing to tolerate an incredibly high rate of unnecessary surgery, even when we know that the surgery won’t do any good. Our addition of new technology seems to make things worse, not better. Everything is going in the wrong direction, even the numbers of women who choose to have the procedure.

Women who have this surgery have complications. Almost half of women who have reconstruction with this procedure require an unanticipated re-operation in the future. In essence, many women are accepting a real risk of future problems while trying to prevent a phantom one.


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