Background: Although many clinical data regarding breast-conserving treatment have already been reported from European and North American countries, few clinical data with long-term follow-up have been reported from Japan.
Method: We collected information on therapeutic and possible or developed prognostic factors and follow-up data for Japanese women who had received breast-conserving treatment consisting of wide excision of the primary tumor, axillary dissection and radiotherapy for unilateral breast cancer considered suitable for breast-conserving treatment from 18 Japanese major breast cancer treating hospitals; 1561 patients were registered.
Results: The median follow-up period was 77 months. Five-year disease-free and overall survival rates were 89.4 and 95.9%, respectively. The 5-year local recurrence-free rate was 96.3%. The patients with histologically positive margins (P < 0.0001) or estrogen receptor negative tumor (P = 0.0340) or younger than 40 years old (P < 0.0001) developed statistically significantly more local recurrences. Adjuvant endocrine therapy was essential for the estrogen receptor positive patients to have a lower local recurrence rate. Endocrine therapy did not change the local recurrence rate among estrogen receptor negative patients at all. Multivariate analysis showed histological margin status and the combination of estrogen receptor status and endocrine therapy were independent prognostic factors for local recurrence.
Conclusion: The 5-year local recurrence rate of Japanese breast cancer patients who were treated with breast-conserving treatment using radiotherapy was 3.7%. Independent prognostic factors for local recurrence were histological margin status and the combination of estrogen receptor status and adjuvant endocrine therapy.