Pattern of tumor recurrence in initially nonmetastatic breast cancer patients: Distribution and frequency of metastases at unusual sites

BACKGROUND. Breast cancer is likely to have systemic involvement. However, to the authors' knowledge there are few reports to date regarding clinically detected patterns of metastasis, meticulously studied in regard to the natural history of breast cancer, including unusual sites of metastasis. METHODS. Patients treated for invasive breast cancer from April 1983 to May 2007 were retrospectively analyzed. Patterns of clinically apparent tumor recurrence, focusing especially on unusual metastases, were studied as well as possible risk factors for unusual metastases and their influence on survival. RESULTS. Overall, 3783 patients were eligible for the current analysis. The median duration of follow-up was 5.0 years (range, 0.6 years-20.4 years). Cumulative 5-year and 10-year survival rates were 89.7% and 81.5%, respectively. "Unusual metastasis" was defined as systemic failure with a frequency of ≤1%; in the current series; it was observed in 85 (2.2%) patients %. Of those, 70 (82%) had preceding metastasis in the usual sites. The median duration until the development of usual and unusual metastasis was 2.3 years and 3.6 years, respectively (P < .0001). Among 764 patients with distant metastasis, the 5-year cumulative overall survival rate in those with or without unusual metastasis was 53.5% and 53.4 years, respectively (P = .33). No risk factors for unusual metastasis were identified. CONCLUSIONS. This retrospective study examined the frequency of unusual metastases in a large number of Japanese patients with initially nonmetastatic breast cancer. The prognosis of patients with unusual metastases was found to be similar to that of patients with metastasis only at more usual sites.