Breast-cancer osteolysis, bone metastases, and anti-osteolytic effect of aspirin

23 (60%) of 38 human breast carcinomas had significant in-vitro osteolytic activity. All patients presenting with bone metastases or hypercalcaemia had active tumours. Over a subsequent three-year follow-up period, bone metastases did not develop in any of the 15 patients with inactive tumours, and metastases at other sites developed in only 2. Of the 23 patients with active tumours, 7 either had, or have since developed bone metastases; in 4 of these hypercalcaemia also developed. 14 tumours, chosen at random, were tested for in-vitro osteolytic activity in the presence and absence of aspirin, which inhibits prostaglandin synthetase. The activity of 8 of the 9 osteolytically active tumours was significantly, though not completely inhibited by aspirin. Although the number of patients is limited, these results indicate that the in-vitro osteolysis assay may detect substances, perhaps including prostaglandins, produced by breast tumours which affect prognosis and contribute to the subsequent formation of bone metastases.