Take-Home Pearl: Radiation therapy (following breast-conserving surgery) for ductal carcinoma in situ (DCIS) reduces the risk of an in-breast (local) recurrence by about half.
The European Organization for the Research and Treatment of Cancer (EORTC) study included patients with DCIS, randomized to either postoperative (adjuvant, or “in addition to”) radiation therapy (N-507) or no additional treatment (N=503). Patients were under 70 years of age, and had DCIS 5cm or smaller. The radiation therapy dose was 50 Gy in 25 treatments over a 5-week period, targeting the whole breast. The use of tamoxifen (“anti-estrogen”) therapy was not specified in the protocol. Margins were deemed negative if they were at least 1mm. Between 1986 and 1996, 1010 women entered the study. Only 5% of the patients who received radiation therapy got a boost (extra radiation to the primary DCIS area).
Results: The median follow-up time was 15.8 years. The 15-year chances of being free of an in-breast recurrence were: 1) No radiation group 69%; radiation therapy group 82%. Type of recurrence were roughly divided evenly between DCIS and invasive cancer. Radiation therapy reduced the risk of local relapse by half. A multivariate analysis showed the following features increased the risk of recurrence: age under 40; detection by clinical exam (and not simply by mammograms); solid or cribriform growth pattern; and involved or close margins.
My Take: Adjuvant radiation therapy following breast conserving surgery for DCIS reduces the risk of an in-breast recurrence significantly. No subgroup could be identified for which radiation therapy did not provide benefit. Given a lack of increase in the high long-term survival rates (98% or so in the literature), the use of radiation therapy should be based on patient preference, overall health status, and life expectancy. Finally, local recurrence rates can be even lower than what was seen in the EORTC trial: To wit, our local recurrence rates at Evergreen Hospital (Kirkland, WA, USA) are 2% at 12 year median follow-up. Perhaps this excellent outcome is due, at least in part, to a demand for good margins, the routine use of adjuvant tamoxifen and whole breast radiation therapy. I’m Dr. Michael Hunter.
Reference: Donker M, et al. J Clinical Oncology 2013;31 (November 10): 4054-4059.
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