The direct inhibition of prostaglandin synthetase of human breast cancer tumor tissue by tamoxifen.

Patients with breast cancer in the early clinical stages often complain of bone pain although they may not have radiologically apparent bone metastases and indeed clinical tests may reveal evidence of hypercalcaemia. There is a high incidence of bone metastases in advanced breast cancer and a well-correlated increase in the incidence of hypercalcuria and hypercalcaemia. It is also known that bone pain can increase dramatically whenever hypercalcaemia develops. We have been impressed by the clinical effects of tamoxifen, which in addition to its anti-oestrogenic properties causing tumour regression has been observed to relieve bone pain in many other patients in the absence of measurable tumour regression and in the absence of recalcification of bone metastases.