Exemestane Prevents Breast Cancer? Maybe. Costly? Definitely

This is the week of the American Society for Clinical Oncology’s meeting so we can expect to inundated with news of medical progress, some real, some maybe real, some imagined. But all can be expected to be costly.

One of the most publicized studies is that of using exemestane (Aromasin) to prevent breast cancer in women at moderately increased risk. 4560 women were randomly assigned to a group using the drug or to placebo. The abstract from an article on the study published this week in the NEJM states:

At a median follow-up of 35 months, 11 invasive breast cancers were detected in those given exemestane and in 32 of those given placebo, with a 65% relative reduction in the annual incidence of invasive breast cancer (0.19% vs. 0.55%; hazard ratio, 0.35; 95% confidence interval [CI], 0.18 to 0.70; P=0.002). The annual incidence of invasive plus noninvasive (ductal carcinoma in situ) breast cancers was 0.35% on exemestane and 0.77% on placebo (hazard ratio, 0.47; 95% CI, 0.27 to 0.79; P=0.004). Adverse events occurred in 88% of the exemestane group and 85% of the placebo group (P=0.003), with no significant differences between the two groups in terms of skeletal fractures, cardiovascular events, other cancers, or treatment-related deaths. Minimal quality-of-life differences were observed.

The drug has fewer side-effects than other agents used to prevent breast cancer (tamoxifen and the aromatase inhibitors) but still in 3-4% of patients severe joint pain was reported.

Medicynical Note: Exemestane (Aromasin) costs about $3600/year. In this study about 2280 (half of the number randomized) patients were treated with exemestane for three years and according to the study 21 fewer cancers occurred than in the placebo group. This reduction of incidence from 32 in placebo to 11 given drug was cited in news articles as a “65% reduction in cancer occurrence.”

The cost of this preventive strategy/case prevented is $3600 (yearly cost) X 3 (number of years treated) X 2280 (number of patients treated)/ 21 (number of cases of cancer prevented) and was $1,172,571/case prevented.

In fact, relatively few cancers occurred in either group (32 and 11). The reduction of 21 cases was significant but the cost/cancer prevented is prohibitive. Given that these patients will also be followed with mammograms and physician exams (adding to the cost) it’s doubtful that this intervention will lead to a measurable survival benefit.


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One response to “Exemestane Prevents Breast Cancer? Maybe. Costly? Definitely

  1. None of these drugs gives you a free ride or guarantees you won’t get BC if you have already had it. Oh yeah, and how about the “cost” in quality of life? Too often quantity seems hold sway over quality, not a good idea in my personal BC view.

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