Reference - JAMA Surg 2015 Jun 3 early online (level 2 [mid-level] evidence)
With the increasing prevalence of mammography for breast cancer screening has come an increase in the diagnosis of ductal carcinoma in situ (DCIS), a spectrum of abnormal cells in the breast ducts not invading surrounding tissues (NIH Consens State Sci Statements 2009 Sep 24;26(2):1). DCIS is associated with an increased risk of invasive breast cancer, but it is also associated with a low risk of breast cancer-specific mortality (Arch Intern Med 2000 Apr 10;160(7):953, Am J Surg 2006 Oct;192(4):416). Although current recommendations suggest primary DCIS treatment should include a lumpectomy plus whole breast radiation therapy (National Comprehensive Cancer Network (NCCN) guideline, Ann Oncol 2011 Sep;22 Suppl 6:vi12), the wide variations in DCIS pathology are associated with differential risks of invasive carcinoma. A recent retrospective cohort study evaluated the effect of surgery on survival in 57,222 women diagnosed with DCIS between 1988 and 2011 in the Surveillance, Epidemiology, and End Results (SEER) database.
Ninety-eight percent of women were treated surgically, of whom 61% had a partial mastectomy and 29% had a mastectomy. Of the 2% of women not treated surgically, 46.8% did not have a physician recommend surgery and 9.8% refused surgery after a physician recommendation. A large percentage of women (40.9%) not having surgery received a physician recommendation for surgery, but the reasons it was not performed were unknown. Over the median follow-up of 72 months, 1% of women died from breast cancer and 6.4% died from other causes. A propensity score-weighted analysis was performed to balance baseline patient characteristics between the surgical and nonsurgical groups. In this analysis, the estimated 10-year breast cancer-specific survival was 98.5% with surgery and 93.4% without surgery (p = 0.003). These results were not consistent across all DCIS nuclear grades, however. While women with high-grade or intermediate-grade DCIS had significantly increased survival with surgery compared to no surgery (98.4% vs. 90.5% for high grade DCIS, p < 0.001 and 98.6% vs. 94.6% for intermediate grade DCIS, p < 0.001), there were no significant differences in breast cancer-specific survival in women with low-grade DCIS (98.6% vs. 98.8%). Consistent results were found in the analysis of estimated 10-year overall survival.
Although this study is only a retrospective database analysis, it is still significant because it included a large number of women who were not treated with surgery, even though this was a small percentage of the total. Given the observational nature of this study, it is not surprising that the characteristics of women were not well balanced between the surgical and nonsurgical groups, but propensity score-weighted analyses were used to adjust for these differences. Surgery was found to significantly increase survival in women with intermediate to high-grade DCIS, in line with the current recommendations. However the failure of surgery to increase survival in women with low-grade DCIS suggests less invasive treatments may be an appropriate option for this subset. Further prospective studies are required to determine the best course of management for women with low-grade DCIS.
For more information, see the Ductal carcinoma in situ topic in DynaMed.