Higher Doses of Arimidex for Heavier Wom

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Higher Doses of Arimidex for Heavier Wom

Posted 7/23/2010

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This is a really interesting study about the best dose of anastrozole (arimidex) for heavier/overweight/obese women. As you may know, chemotherapy doses are determined by a formula involving height and weight. It would make sense, common-sense wise, that the same would be true for other medications. Turns out, at least in this case, that is so. Here is an article from MedWire and then a link to read an editorial in the Journal of Clinical Oncology (where the study was published).

Higher doses of anastrazole required in overweight breast cancer patients

By Laura Dean

20 July 2010

J Clin Oncol 2010; 28: 3411-3415

MedWire News: The relative efficacy of anastrozole compared with tamoxifen is greater in postmenopausal women with a healthyweight than in their overweight peers, researchers report.

In their study of 4939 women postmenopausal women with early-stage breast cancer, Ivana Sestak (University of London, UK) and colleagues investigated the impact of body mass index (BMI) on disease recurrence, and the relative benefit of anastrozole versus tamoxifen according to baseline BMI.

They predicted that, as aromatase inhibitors work by inhibiting the conversion of androgens to estrogens in adipose tissue, anastrozole may be more effective than tamoxifen in women with a high BMI, defined as>35 kg/m2.

The researchers report that after a median of 100 months of follow-up, 878 (18%) women had experienced breast cancer recurrence.

Overall, women with a high BMI at baseline had 39% more recurrences and 46% more distant recurrences than women with a low BMI (below 23 kg/m2).

Furthermore, women receiving anastrozole had a 27% lower recurrence rate than those on tamoxifen, and recurrence rates in the anastrozole group were lower than those in the tamoxifen group at all BMI levels.

However, the benefit of anastrozole compared with tamoxifen was non-significantly greater in women with a low BMI than in overweight women. Anastrazole was associated with a 36% reduced risk for recurrence compared with tamoxifen in women with a BMI below 23 kg/m2, and a 16% reduced risk for recurrence in women with a BMI above 30 kg/m2.

"One possible explanation for our findings is that higher estrogen levels resulting from a high BMI may lead to incomplete inhibition with anastrozole," write Sestak and co-authors in the Journal of Clinical Oncology.

"Therefore, women with a high BMI might need higher dosages to achieve the full antitumor efficacy of this drug," the researchers suggest. "To evaluate this, a study of estrogen suppression by aromatase inhibitors according to BMI levels might be useful," they conclude.