ASCO 2011: Cost effectiveness Zoledronic Acid (Zometa) vs Denosumab (Prolia, Xgeva)

There were very few cost efficacy studies at the recent ASCO meetings.

One set of three studies sponsored by the drug company (Novartis) compared zoledronic acid with denosumab made by Amgen. The abstracts looked at the cost of a QALY (quality adjusted life year) in patients with metastatic prostate cancer (abstract 1), and breast cancer (abstract 2). The third was an economic evaluation (abstract 3) comparing the costs of preventing a skeletal related event in prostate cancer. Not surprisingly, since they were sponsored by Novartis, these studies “confirmed” that zoledronic acid was more “cost effective.”

The studies found that while zoledronic acid is slightly less effective than denosumab in preventing skeletal related events, denosumab is more expensive.

From abstract 1:

Compared to ZOL (Table), Dmab resulted in fewer SREs, more QALYs, and lower SRE-related costs, but higher drug-related and total costs ($5,313). Overall, Dmab resulted in an incremental cost of $1,250,000 per QALY gained.

From abstract 2:

Dmab resulted in fewer SREs, more QALYs, and lower SRE-related costs, but higher drug-related and total costs vs. ZOL, resulting in an incremental cost of $6,884/pt (Table). The cost per QALY gained was $644,000 when excluding SAEs ($613,000/QALY when including SAEs).

It is telling, and perhaps reflects a “strategic” omission, that neither abstract 1 or 2 reveals zoledronic acid’s cost of a QALY gained.

However, abstract 3 gives a better indication of the relative costs and efficacy of the approaches.

The total costs incurred over one year were estimated at $37,854 for denosumab and $30,499 for ZA, with an incrementally higher cost of $7,355 for denosumab. The estimated number of SREs during the one-year period was 0.56 for denosumab and 0.67 for ZA, where the denosumab patients had 0.11 fewer SREs.

QALY= quality adjusted life year
SRE= Skeletal related event

Medicynical Note: What is unstated in these cost comparison studies is that none of the current generation of treatments to prevent bone events including zoledronic acid and the newer monoclonal, denosumab, meet the guideline for cost effectiveness. (a QALY at a cost of less than $50,000-$100,000.

A study in the Journal Urology in 2004 compared the outcomes of patients getting zoledronic acid with patients receiving placebo and noted:

The nominal cost per skeletal complication avoided was US dollars 112300 (95% CI US dollars 6900 to US dollars 48700) and the cost per additional patient free of skeletal complications was US dollars 51400 (95% CI US dollars 26900 to US dollars 243700). Nominal within-trial cost per quality adjusted life-year was US dollars 159200, which varied widely in sensitivity analyses.

To put it in perspective, in 2004 when drug costs were much lower than now, the health care non-system in the U.S. spent over $50,000 to save one additional skeletal complication. That approximates the yearly median income in our country.