Voluntary guidelines were updated by the American Society of Clinical Oncology in 2003. Evidence is based on studies showing a reduction at 12 months in the number of skeletal related events (SRE: pathological fracture, cord compression or requirement for radiation of bony metastases, or hypercalcaemia) in patients randomised to receive bisphosphonate (mainly pamidronate) versus placebo.r In two major studies,rr the SRE rate was reduced by 10-14%, from a baseline level of around 56%, with subsequent trials of zolendronic acid demonstrating equivalent efficacy but increased convenience over APD (15 v 90 minute administration time).r
There is minimal data regarding efficacy of less frequent administration, or the efficacy of continuing the drug once a skeletal related event has occurred.r There is significant data to demonstrate that bisphosphonates are frequently administered to patients not meeting the guideline criteria.r It has also been observed that the SRE rate in clinical practice is lower than that reported in the large clinical trials, perhaps due to less frequent imaging.rr