The treatment outcome of patients undergoing breast-conserving therapy: the clinical role of postoperative radiotherapy.

Background: Treatment outcome was evaluated in patients who underwent breast-conserving therapy and tangential irradiation. After verifying background factors including systemic therapy, the clinical efficacy of postoperative irradiation was investigated.
Method: There were 708 study subjects, all of whom had early breast cancer treated between 1992 and 2002. The median follow-up period was 83 months. After breast-conserving surgery, in patients with negative surgical margins, only tangential irradiation at 48 Gy/24 fr was performed. In contrast, in those with positive surgical margins, 10 Gy of radiation boost to the tumor bed with electrons was administered after tangential irradiation with 50 Gy/25 fr. Treatment outcome was analyzed using the Kaplan-Meier method and Cox's proportional hazards regression model.
Results: The disease-free survival and no-recurrence rates within the ipsilateral breast after 5 years were 93.4 and 97.2%, respectively. Risk factors for recurrence within the ipsilateral breast included younger age of patient, the number of positive lymph nodes, and no endocrine therapy. However, the surgical margin was not a risk factor. Risk factors for relapse outwith the ipsilateral breast included younger age, the number of positive lymph nodes, and recurrence within the ipsilateral breast.
Conclusions: From our analysis of 708 Japanese women who received breast-conserving therapy, which can be regarded as a standard method in Japan, the treatment outcome was compatible with previous reports from other countries.