Cosmetic evaluation of breast conserving treatment for mammary cancer. 2. A quantitative analysis of the influence of radiation dose, fractionation schedules and surgical treatment techniques on cosmetic results.

Abstract

The effects of surgical treatment techniques, radiation doses and fraction sizes on cosmetic outcome were analysed in a population of 161 patients with stage I and II breast cancer treated with breast conserving surgery and a wide range of radiotherapy doses. In 142 patients also quantitative measurements of nipple position asymmetries and breast contour retraction were carried out. The scoring and measurement results were analysed using a multivariate model to assess the relative importance of the various factors involved. In this material radiation dose to the breast was the most significant parameter correlated with cosmetic outcome (p = 0.0001). Radiation doses higher than 75 Gy in 37 fractions led to very poor results in more than 30% of patients. For the quantitative measurements of radiation fibrosis, a dose-response curve could be demonstrated over a dose range of 40 to 86 Gy in fraction sizes of 2 Gy. Above 50 Gy, increases in dose of 1 Gy correlated with an average displacement of nipple and breast contour of 1 mm, in upward direction and of 0.75 mm to the median. An increased amount of fibrosis was observed when part of the treatment was given in larger fraction sizes (4-6 Gy). Plotting the data against dose equivalent TE values, an alpha/beta value of 2.5 Gy could be estimated for the development of late fibrosis. Other treatment factors whose influence on cosmetic outcome could be identified and quantified were the differences in surgical techniques for the removal of the primary tumor (tumorectomy vs. segmentectomy, p = 0.05) and for the axillary clearance ("en bloc" dissection vs. separate incisions, p = 0.018). Also technical aspects of the radiotherapy on the regional lymph nodes, sometimes leading to matchline fibrosis, proved to be important (p = 0.0075). Finally, a number of tumor-related factors were assessed in order to take their relative importance into account, if necessary, when studying therapy factors. While tumor stage had only a limited impact in the range of tumors included in this study, the localisation of the tumor significantly influenced cosmetic outcome with worse results for inferior and medial localisations. While quantitative measurements were not correlated with all the factors identified for poor cosmesis, their great value is to quantify the radiation-induced fibrosis as well as the effects of different surgical techniques on nipple retraction.