Tumor ‘Flare’ Hypercalcemia – An Additional Indication for Bisphosphonates?

Abstract

The most serious, potentially life-threatening manifestation of ‘flare’ is hypercalcemia, registered in 4–5% of breast cancer patients with bone metastases, usually during the first few weeks of tamoxifen treatment. There are no specific treatment recommendations for flare hypercalcemia, except tamoxifen withdrawal. There are no reports on the use of bisphosphonates in the treatment of flare hypercalcemia. Among 87 hypercalcemic patients with metastatic breast cancer observed during a 7-year period, 10 patients had tamoxifen-induced hypercalcemia. Diagnosis of flare hypercalcemia was based on the normal pretreatment values of serum calcium and the development of hypercalcemia within a maximum of 6 weeks of hormonal drug initiation. The median time from hormonal drug initiation to flare hypercalcemia was 14 days, the median duration 8.5 days, and the median calcium level was 3.09 mmol/l (range 2.79–4.46 mmol/l). All patients were treated with hydration, and 7 patients with calcium levels above 3.0 mmol/l were also treated with disodium pamidronate in various single doses (30–90 mg/24 h). Normocalcemia was achieved in all patients, and tamoxifen was continued without relapse of hypercalcemia. Median survival was 177 days (range 12–570 days). It seems that the use of bisphosphonates in the treatment of flare hypercalcemia could allow safe readministration of tamoxifen and prevent premature and unjustified tamoxifen discontinuation. Flare hypercalcemia might represent one more indication for the use of bisphosphonates.