Incidence and patterns of distant metastases for patients with early-stage breast cancer after breast conservation treatment.

BACKGROUND: Breast conservation treatment (BCT), consisting of breast conservation surgery followed by definitive radiation therapy (RT), has been shown to be effective for early-stage breast cancer. Patterns of metastatic failure by specific anatomic site are not well described in the literature.
METHODS: A total of 1754 patients with stage I or II invasive carcinoma of the breast treated with BCT between 1977 and 2003 were identified. Patients were scored based on first site of metastasis: bone, brain, lung, liver, or other. Non-breast cancer deaths, contralateral breast cancer, and second malignancies were treated as competing risks events. Cumulative incidence functions for each competing event were calculated using competing risk methodology. Univariate analysis was performed to determine the hazard ratio (HR) associated with patient and tumor characteristics.
RESULTS: The most common event was non-breast cancer death (16.5% at 15 years; 95% confidence interval [CI], 13.9%-19.4%). The most common exclusive first site of metastasis was bone (5.9% at 15 years). The 4 most common anatomic sites of distant metastases as the first exclusive event were bone (41.1%), lung (22.4%), liver (7.3%), and brain (7.3%).
CONCLUSION: The present study has demonstrated the site-specific risks of metastases. These data support current clinical practice of screening for site-specific metastatic disease after BCT based on concerning patient-specific signs or symptoms.