Pharmacoeconomics of bisphosphonates for skeletal-related event prevention in metastatic non-breast solid tumours

Bisphosphonates reduce the risk of skeletal-related events (SREs; i.e. spinal cord compression, pathological fracture, radiation or surgery to the bone, and hypercalcaemia) in patients with metastatic cancer. A number of analyses have been conducted to assess the cost effectiveness of bisphosphonates in patients with bone metastases secondary to breast cancer, but few in other solid tumours. This is a review of cost-effectiveness analyses in patients with non-breast solid tumours and bone metastases. A literature search was conducted to identify cost-effectiveness analyses reporting the cost per QALY gained of bisphosphonates in patients with metastatic bone disease secondary to non-breast solid tumours. Four analyses met inclusion criteria. These included two in prostate cancer (one of which used a global perspective but expressed results in $US, and the other reported from a multiple country perspective: France, Germany, Portugal and the Netherlands). The remaining analyses were in lung cancer (in the UK, France, Germany, Portugal and the Netherlands), and renal cell carcinoma (in the UK, France and Germany). In each analysis, the cost effectiveness of zoledronic acid versus placebo was analysed. Zoledronic acid was found to be cost effective in all European countries across all three indications but not in the sole global prostate cancer analysis. Across countries and indications, assumptions regarding patient survival, drug cost and baseline utility (i.e. patient utility with metastatic disease but without an SRE) were the most robust drivers of modelled estimates. Assumptions of SRE-related costs were most often the second strongest cost driver. Further review indicated that particular attention should be paid to the inclusion or exclusion of nonsignificant survival benefits, whether health state utilities were elicited from community or patient samples or author assumptions, delineation between symptomatic and asymptomatic SREs, and the methods with which SRE disutility was modelled over time. While the field of cost-effectiveness analysis in solid tumours other than breast cancer is still evolving, outcomes will likely continue to be driven by drug cost and assumptions regarding treatment benefits. Although considerations such as adverse events and administration costs are important, they were not found to influence cost-effectiveness estimates greatly. As zoledronic acid will lose patent protection in 2013 and subsequently be greatly reduced in price, it is likely that the field of cost effectiveness will change with regard to SRE-limiting agents. Meanwhile, research should be conducted to improve our understanding of the impact on quality of life and medical costs of preventing SREs.