Growth fractions (Ki-67) in primary breast cancers, with particular reference to node-negative tumors.

We determined the growth fraction in 549 primary breast carcinomas using monoclonal antibody Ki-67. With respect to the course of disease, significant differences emerged for the whole collective as well as among the node-positive tumors. We paid special attention to the node-negative (N0) carcinomas in the group, the aim being to differentiate a prognostically unfavorable subgroup in this otherwise favorable collective. Owing to the comparative rarity of clinical events, our findings for such tumors failed to attain statistical significance; however, a strong clinical trend indicating an adverse prognosis for both overall and disease-free survival emerged for tumors exhibiting a high growth fraction. One-quarter of these patients had received adjuvant treatment. In the group exhibiting high levels of Ki-67 reactivity, significantly less favorable findings with respect to overall survival were observed among the untreated patients. The present results seem to confirm previous indications that antibody Ki-67 is of value in assessing the prognosis of N0 breast cancer.