Cosmetic outcome in patients receiving an interstitial implant as part of breast-conservation therapy.

Abstract

To study factors related to breast cosmetic outcome in patients treated with an interstitial implant as part of breast-conservation therapy. One hundred fifty-six patients with stage I or II breast carcinoma who received 50 Gy of external-beam irradiation followed by a 20-Gy interstitial boost were examined. The dose homogeneity index (DHI) was calculated for each evaluable implant and was examined in light of other patient-, treatment-, and tumor-related variables previously demonstrated to affect cosmesis. Of the variables examined, both the DHI (P = .021) and the total excision volume (P = .019) were significantly related to cosmetic outcome (excellent vs less than excellent) in a univariate model. In the multivariate analysis, only the total excision volume remained significant (P = .032). The mean total excision volume +/- SD in patients with excellent cosmetic outcome (81.8 cm3 +/- 84.0) was significantly less than that in patients with less than excellent cosmetic outcome (120 cm3 +/- 84). The probability of excellent cosmetic outcome linearly increased with an increase in DHI. The mean DHI was 0.74 +/- 0.12 for the cases with excellent cosmetic outcome and 0.68 +/- 0.10 for those with less than excellent cosmetic outcome. To achieve optimal cosmesis, DHI should be maximized. The volume of tissue removed, however, remains the most significant determinant.