1. Adjuvant radiotherapy (RT) following local excision reduces the risk for local recurrence (LR) of ductal carcinoma in situ (DCIS) by half at 15 years follow-up.
2. The long-term prognosis of DCIS is favorable and independent of given treatment.
Evidence Rating Level: 1 (Excellent)
Study Rundown: Preventive cancer screenings have significantly increased the incidence of ductal carcinoma in situ over the last few decades, raising questions about its optimal treatment. RT has already been shown to halve the risk of local recurrence following conservative excision; however, long-term follow-up of large clinical trials is necessary to determine whether RT should be standardized as a part of the conservative management of these patients. Therefore, the authors of this study investigated the effect of RT on long-term outcomes regarding recurrence and survival in women treated conservatively for DCIS. By comparing patients who had undergone excision + RT or excision alone at a median follow-up time of 15 years, the authors found that radiotherapy reduced the risk of local recurrence by half. However, though patients who had experienced recurrence had worse survival, they found no significant differences in breast cancer-specific or overall survival between the two treatment arms. Therefore, it remains unclear what effect, if any, adjuvant RT has on long-term survival.
The study benefits from a randomized, controlled design, a large patient population and a long follow-up time. However, future studies that consider even larger populations with more remote follow-up times may be necessary to make any conclusions regarding the effect of RT on long-term survival. Furthermore, this study did not analyze the effect of tamoxifen on outcomes. It is also possible that factors other than RT are involved in decreasing risk of local relapses.
In-Depth [randomized controlled trial]: The authors of this study used the data from 1010 women from the EORTC 10853 trial who were randomly assigned to local excision + RT or local excision alone. All of these patients were treated between 1986 and 1996, were under 70 years old, and had unilateral lesions up to 5cm in diameter without evidence of invasion and who underwent LE. The median follow-up was 15.8 years. The primary outcomes measured were local recurrence and both breast cancer-related and unrelated deaths. The authors found that adjuvant treatment with RT after excision halved the risk of LR (P < 0.001), as the 15-year LR-free rats were 69% in the excision-only group and 82% in the adjuvant group. Adjuvant RT reduced the risk of pure DCIS LR (P = 0.003) and invasive LR (P = 0.007). There was no significant difference in breast cancer-specific survival (P = 0.814) or overall survival (P = 0.931). On the basis of these findings, the authors concluded that adjuvant RT decreases the 15-year risk of local recurrence, but also that the effect of this treatment on long-term prognosis and survival is unclear.
By Monica Parks and Andrew Bishara
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