Ipsilateral breast tumor recurrence (IBTR) after breast-conserving treatment for early breast cancer: risk factors and impact on distant metastases

BACKGROUND: The clinical features of ipsilateral breast tumor recurrence (IBTR) after breast conserving therapy (BCT) for early stage breast cancer were analyzed from long-term follow-up of BCT in Japan. The purpose of this study was to clarify risk factors of IBTR and the impact of IBTR on development of distant metastases in this ethnic group. METHODS: Patients (N = 1901)with unilateral breast cancer < or = 3 cm in diameter who underwent BCT at 18 Japanese major breast cancer treatment institutes from 1986 to 1993 were registered in this study. Survival rates, the incidences of IBTR and distant metastases, and annual rates of IBTR and distant metastases after primary operation were calculated by the Kaplan-Meier method. A Cox proportional hazards model was used to estimate the risks of IBTR and distant metastases. A Cox model was also used to estimate the risks of distant metastases after IBTR in the group of IBTR. RESULTS: At a median follow-up time of 107 months, the 10-year overall and disease-free survival rates were 83.9% and 77.8%, respectively. The 10-year cumulative rates of IBTR were 8.5% in the patients with postoperative irradiation and 17.2% in the patients without irradiation. The 10-year cumulative distant metastasis rate was 10.9%. On multivariate analysis, young age, positive surgical margin, and omission of radiation therapy were significant predictors of IBTR. In addition, IBTR significantly correlated with subsequent distant metastases (hazard ratio, 3.93; 95% confidence interval, 2.676-5.771; P < 0.0001). Among patients who developed IBTR, initial lymph node metastases and short interval to IBTR were significant risk factors for subsequent distant metastasis. CONCLUSIONS: Young age, positive surgical margin, and omission of radiation therapy seemed to be important factors in relation to local control. The authors' results also indicated that IBTR is significantly associated with subsequent distant metastasis. Patients with positive nodal status at primary operation or with short interval from primary operation to IBTR are at especially high risk of distant metastasis. It remains unclear, however, whether IBTR is an indicator or a cause of subsequent distant metastases.