By: Dr. Geoffrey Modest
There was an important note of caution in an article in JAMA, finding that more women are getting bilateral mastectomies to treat unilateral cancer, with data suggesting this might be harmful (see doi:10.1001/jama.2014.10707). This was observational cohort study in the population-based California Cancer Registry from 1998-2011, with median follow-up of 89.1 months. Findings:
–189,734 patients with unilateral early-stage breast cancer were followed. Excluded those with tumor >5cm/paget’s/mammographic diagnosis only.
–Rate of bilat mastectomies was 2.0% in 1998, increasing to 12.3%!!! in 2011. unilateral decreased from 46.3 to 33.4% and breast-conserving surgery with radiation was pretty stable at 51.7 to 54.2%.
–More specifically, re: bilateral mastectomies:
–In those <40yo, the rate increased from 3.6% to 33%
–Was more in those receiving care in National Cancer Institute-designated cancer center: 8.6% vs 6.0%
–Was most common in non-Hispanic whites at 6.9%, others in the 3-5% range; unilateral mastectomy more common in racial/ethnic minorities — Filipina 52.8%, Hispanic 45.6%, vs non-Hispanic whites 35.2%
–Tracked with neighborhood socioeconomic status quintile (highest rate in highest SES communities). also with private insurance (7.7%) vs public/medicaid (3.3%). unilateral mastectomy also more with public/Medicaid insurance 48.4% than with private insurance (36.6%).
–10-year mortality, compared with breast-conserving surgery with radiation (16.8%): unilateral mastectomy 20.1%. Bilateral mastectomy 18.8% (nonsignif difference for bilat)
So, large increase in bilateral mastectomy in certain populations (esp privately-insured non-Hispanic whites who went to NCI-designated cancer centers), with no evident benefit after 10 years (of note, their Figure 2 shows data up to 15 years post-surgery, with leveling off of curves from 12-15 years). Those with unilateral mastectomy did worse in this and other observational studies. what are the factors explaining these changes? Those with unilateral mastectomy may have had tumors with worse prognosis (eg lymphovascular invasion or extranodal extension — items not recorded in this registry). And the above data suggests a shift from unilateral to bilateral mastectomies. Perhaps part of the issue is the role of breast MRI, which finds all kinds of difficult-to-interpret abnormalities, perhaps leading to more aggressive/bilateral surgery (ie, too much information….). Role of genetic testing (though there are pretty good short-term outcome data that bilat mastectomy is associated with improved prognosis in those with BRCA 1/2, though that is a small % of breast cancers). But, not surprisingly, bilateral mastectomy is associated with more adverse effects (including both those directly related to the surgery, such as flap failure, necrosis, infection, as well as some studies reporting bad effects on body image, sexual function and quality of life). Bottom line: we will probably never get a clear RCT with definitive answers, so we do need to look at these observational studies. Lots of data are collected in the cancer registries, but we can never be sure that there wasn’t a significant bias in who got more extensive surgery. But women should understand that for other than those positive for BRCA 1/2, the current observational data do not support a clinical benefit from more aggressive surgery and that there are real potential hazards. By the way, there is a really great book “The Emperor of All Maladies” by Siddhartha Mukherjee, which tracks the history of cancer and how its conception and approach to therapy over time reflects the overall dominant social ideology of the period; the book has a special focus on breast cancer.