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Radiation therapy plus lumpectomy is associated with better survival than total mastectomy in women with DCIS

WCH study finds lumpectomy plus radiation associated with a small clinical benefit in reducing the risk of breast cancer death in women with ductal carcinoma in situ (DCIS)

August 10, 2018  |  Download Release

Toronto, August 10, 2018 – 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:  Vasily Giannakeas, MPH, Victoria Sopik, MSc, and Steven A. Narod, M.D., of Women’s College Research Institute and the Dalla Lana School of Public Health at the University of Toronto. Giannakeas and Sopik are doctoral students of Dr. Narod.

Results: Among 29,865 women treated with mastectomy, there were 240 in breast recurrences and 254 deaths from breast cancer. Among the same number of women treated with lumpectomy and radiation there were 621 in breast recurrences and 207 deaths from breast cancer. A small improvement in breast cancer survival was associated with radiation plus lumpectomy for DCIS (25 per cent reduction in deaths). The absolute risk reduction was small, making it necessary to treat 370 women with radiotherapy to save one life. However, the beneficial effect was much stronger for young women, black women and women with large DCIS lesions.

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.

Study Conclusions: Among patients with DCIS, treatment with lumpectomy and radiotherapy is associated with better survival than patients who were treated with total mastectomy – a much more extensive surgery. This surprising result suggests that in a small proportion of patients with DCIS the cancer has spread beyond the breast at the time of diagnosis and can be treated successfully with radiotherapy. This observation supports our previous position that DCIS better resembles a small invasive cancer than a precursor lesion. It is intriguing that radiotherapy has this beneficial effect, which appear to be attributable to systemic activity rather than local control. Future studies should examine how radiotherapy affects survival.


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