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) according to research published online in JAMA Network Open.

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.
More than 140,000 U.S. women who had DCIS between 1998 and 2014 were included in this study.  The study compared lumpectomy plus radiation vs. lumpectomy alone, lumpectomy vs. mastectomy, and lumpectomy plus radiation vs. mastectomy

The study measured use of radiation and/or extent of surgery (exposures) and breast cancer mortality rates within 15 years (outcomes).

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.

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.

A limitation of the study is that some data were missing.  For example, 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.

Steven A. Narod, M.D., of Women's College Research Institute, in Ontario, Canada, was the lead author of the study.

The invited commentary, "Systemic Effects of Radiotherapy in Ductal Carcinoma In Situ," by Mira Goldberg, M.D., and Timothy J. Whelan, B.M., B.Ch., of McMaster University, Ontario, Canada, was published in the same issue.

Mr. Giannakeas is supported by the Canadian Institutes of Health Research Frederick Banting and Charles Best Doctoral Research Award.  Maria Eberg, MSc (Cancer Care Ontario), contributed to the review of the statistical methods and approach. No financial contribution was received by Ms. Eberg.