The zoledronic acid (Zolmeta) study reported:
“The women were premenopausal and were receiving hormone therapy – either tamoxifen or anastrozole – to prevent recurrence of their tumors. Half the women also received Zometa.”
It should be emphasized that this study was in pre-menopausal women. The results do not necessarily apply to older women–in whom 75% of breast cancers occur.
The ASCO abstract of the study stated:
“With median follow-up of 60 mo (March 31, 2008), 137 (7.6%) DFS events and 42 (2.3%) deaths have occurred. There was no significant difference in DFS between patients who received TAM alone vs ANA alone (HR = 1.10 [95% CI = 0.79, 1.54]; P = 0.59). However, endocrine therapy plus ZOL significantly reduced the risk of DFS events by 36% “
Lets look at that 36% figure. The difference (reported in news articles) between the the two groups was that 9% of those receiving hormone therapy alone recurred while 6% recurred when zoledronic acid was added. This is in absolute numbers a 3% difference between treated and untreated–and could be due to a small difference in disease severity between the groups or actual benefit from the drug. In any case the people promoting this study at some point decided that a 3% benefit doesn’t sound impressive enough so the investigators call it a 35% reduction of risk (9% to 6%). While technically right in their claim, it, in reality, is just a 3% absolute decrease in recurrence in the study group.
Looked at another way 91% of those treated with hormone blockers and 94% of those with the added zoledronic acid were disease free at the end of the study–even less impressive.
As a matter of fact after 5 years one cannot be sure whether patients will recur later and even out the recurrence rate. The delay in recurrence is a real benefit particularly if it is associated with a survival benefit–which has not yet been proven with this drug. So more time will need to pass to fully understand the benefits of this intervention.
In media reports there were no analyses of cost implications of the use of this drug.
The cost of zoledronic acid is about $2000/year, not a huge number but consider, in order to get the 3% improvement, you need to treat all the patients diagnosed with breast cancer receiving hormonal blocker adjuvant therapy. That means the costs for zoledronic acid in 100 cases will be $200,000 or about $66,000 for each of the 3 patients in 100 who benefit from the drug treatment.
For the health care system (and the pharmaceutical manufacturer) the financial aspects may be profound–particularly if the results are extended to post menopausal patients. There are about 185,000 new cases of breast cancer/year. If you figure that 100,000 patients require adjuvant therapy (therapy to prevent recurrence after surgery) that means a cost to the system of $200 million dollars/year to delay recurrence (some of these may be cures) in 3000 women. These costs are in addition to the cost of surgery, physicians, hormone blocker costs etc.
More study necessary? Of course. Cost effective? It’s anybody’s guess. Shouldn’t cost data be a part of the analysis of new interventions? I can’t think of a reason to not have such analysis.
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