Bottom Line: Lumpectomy plus radiation was associated with a small clinical benefit in reduced risk of breast cancer death compared with lumpectomy or mastectomy alone in women with ductal carcinoma in situ (DCIS), a noninvasive early form of breast cancer.
Why The Research Is Interesting: Patients with DCIS are often treated with radiation after lumpectomy, although it has remained unclear whether this can reduce the risk of dying from breast cancer.
Who and When: More than 140,000 U.S. women who had DCIS between 1998 and 2014; this study compared lumpectomy plus radiation vs. lumpectomy alone, lumpectomy vs. mastectomy, and lumpectomy plus radiation vs. mastectomy
What (Study Measures and Outcomes): Use of radiation and/or extent of surgery (exposures); breast cancer mortality rates within 15 years (outcomes)
How (Study Design): This was an observational study. Researchers were not intervening for purposes of the study and cannot control all the natural differences that could explain the study findings.
Authors: Steven A. Narod, M.D., of Women's College Research Institute, in Ontario, Canada, and co-authors
Results: A small improvement in breast cancer survival was associated with radiation plus lumpectomy for DCIS. The absolute risk reduction was 0.27 percent, making it necessary to treat 370 women to save one life. Patients who had lumpectomy plus radiation had more local recurrences than the mastectomy patients but had fewer deaths.
Study Limitations: Some data were missing; investigators didn't have information on tamoxifen use; treatments in the study population weren't randomly assigned; and the possibility remains that the decision to undergo radiotherapy was associated with other favorable prognostic factors.