• R Heimann, C Powers, H J Halpem, A G Michel, C A Ewing, B Wyman, W Recant, and R R Weichselbaum.
• Department of Radiation and Cellular Oncology, Pritzker School of Medicine, University of Chicago, Illinois, USA.
• Cancer. 1996 Oct 15; 78 (8): 1722-30.

BackgroundAlthough breast conservation has received increased acceptance, there are still unresolved issues regarding local treatment techniques, such as the extent of surgery, in relation to the final margins of excision and the use of tumor bed boost radiation. The goal of this study was to determine the local control and breast preservation with particular emphasis on the importance of the final microscopic margins in patients receiving tumor bed boost therapy.MethodsThe authors analyzed 869 cases of Stage I and II breast carcinoma in 852 women who were treated with breast-conserving surgery and radiation therapy between 1984 and 1994. The median follow-up was 43 months. Final microscopic margins were negative in 762 (88%), microscopically positive in 82 (9%), and unknown in 25 (3%) of the patients. Negative margins were defined as no tumor cells at the surgical margin. The patients were treated with external beam radiation therapy to the entire breast to a median dose of 46 Gray (Gy). A boost to the tumor bed was delivered to 863 (99%) of the patients. The median tumor bed dose was 60 Gy. A multivariate analysis of factors impacting on the local control and overall survival was performed. Variables introduced into the model included size, age, lymph node status, microscopic margins, nuclear grade, histologic grade, and estrogen and progesterone receptor status.ResultsThe actuarial 5-year local control rate was 97%. The median time to local failure was 32 months (range, 14-69 months). In multivariate analysis, the only significant factor affecting local control was the status of margins. In patients receiving boost radiation to the excision site, the local control rate at 5 years was 98% and 89%, respectively, if the margins were negative or positive (P < 0.01). This resulted in 5-year actuarial breast preservation rates of 98% and 92% (P = 0.03). In the patients in whom the margins of excision were microscopically positive, the local control rate was 91% if the total dose to the tumor bed was > 60 Gy compared with 76% for a dose < or = 60 Gy (P = 0.05). The 5-year actuarial overall survival rate was 89%. Approximately 94% of the women considered their cosmetic outcome good to excellent.ConclusionsBy obtaining microscopically negative margins and using tumor bed boost therapy, excellent local control, breast preservation, and cosmesis can be achieved. In patients with microscopically positive margins, an acceptable local control rate can be achieved if a tumor bed boost is given.

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