Breast cancer: implications of tumor cell kinetics on clinical outcome.

The relevance of tumor proliferative activity as an indicator of biologic aggressiveness was analyzed on a series of 506 patients with primary breast cancer. In 258 patients with operable tumors without nodal and distant metastases, none of whom was subjected to postoperative irradiation or systemic adjuvant therapy, proliferative activity was significantly correlated with prognosis; 6-year relapse-free survival (RFS) and overall survival (OS) were higher for patients with slowly proliferating tumors for patient with fast-proliferating tumors (RFS: 80.5% vs 59.6%, p = 0.00004; OS: 90.8% vs 74.4%, p = 0.002). On a series of 196 patients with node-positive operable tumors, subjected to 6 or 12 cycles of cyclophosphamide, methotrexate and 5-fluorouracil, a trend in favor of longer 6-year RFS was observed for patients with slowly proliferating tumors than for patients with fast-proliferating tumors (62.5% vs 48.3%, p = 0.08), whereas proliferative activity did not influence OS. In 52 patients with locally advanced disease treated with a multimodality approach, including chemotherapy (adriamycin and vincristine), surgery or radiotherapy, tumor proliferative activity was a strong indicator of biologic aggressivity, since women with slowly proliferating cancers had a higher 4-year probability of OS than women with fast-proliferating tumors (68.1% vs 36.7%, p = 0.02).