Predicting distant dissemination in patients with early breast cancer.

BACKGROUND: Prediction of distant metastases is of paramount importance in the knowledge and management of breast cancer patients. The objective of this study was to assess conventional prognostic factors in a large database of patients with early breast cancer, including those with small tumors diagnosed through regional screening, to determine the risk of distant dissemination. METHODS: The study included 4,797 patients of the Stockholm database who did not receive systemic adjuvant treatments. The main endpoint was metastasis free-interval. Individual risks of distant metastasis were estimated using the regression coefficients of the significant prognostic factors in Cox multivariate analyses. For each level of metastatic risk the pattern of failure was analyzed by a model assuming competing risks. RESULTS: The three independent significant prognostic factors were histologic tumor size, number of involved axillary lymph nodes and progesterone receptor level. However, the latter factor added limited additional information of borderline clinical significance. Thus, subsequent estimations were done with a prognostic score taking into account only the former two most performant factors in the whole population. The risk of distant metastasis of observed values of tumor size categories fitted with published results of a series containing significantly larger tumors. A large variation of tumor size predicts 10-year distant metastasis risk ranging from below 10% up to 90%. Tumors of 10 mm or less had a 10-year metastatic risk of less than 10%. CONCLUSIONS: The results of this study are consistent with a linear effect of tumor size, within the range of data, on 10-year distant dissemination probabilities. Further refinement on prognostic value is needed for tumors of 15 mm or less.