Urokinase-type plasminogen activator (u-PA) is a key protease in cancer invasion and metastasis. Recent studies demonstrated that u-PA, plasminogen activator inhibitor type-1 (PAI-1), and tissue-type plasminogen activator (t-PA) are prognostic factors in breast cancer. However, there have been no prospective studies of node-negative breast cancer on a multicenter basis. On the other hand, some patients, even those with node-negative breast cancer, developed recurrence, and only tumor size is available as a predicting factor in this group. Therefore, it is necessary to find other prognostic factors in node-negative breast cancer to determine suitable adjuvant therapies. Tissue samples in this prospective study were obtained from 130 patients with node-negative invasive breast cancer who underwent radical operation at four hospitals. The median follow-up was 52.6 months. u-PA, PAI-1, and t-PA antigen levels were assayed by ELISA kits using the cytosolic fractions of tumors. Patients with high u-PA, high PAI-1, or low t-PA had significantly higher relapse rates than did those with low u-PA, low PAI-1, or high t-PA, respectively, by the Kaplan-Meier method (P = 0.006, 0.032, and 0.028, respectively). Analyses of the combinations of both u-PA and PAI-1 or both u-PA and t-PA showed that the differences in relapse rate between the high- and low-risk groups were statistically very significant. In the univariate analysis, u-PA, PAI-1, t-PA, progesterone receptor, and tumor size (T3 versus T1) were significantly correlated with relapse. However, the multivariate analysis revealed that only u-PA (P = 0.023) was an independent prognostic factor. This study showed that u-PA was a new significant independent prognostic factor in node-negative breast cancer.

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