Obese women undertreated for breast cancer

08/23/05

EMBARGO: 00:01H (London time) Wednesday August 24, 2005. In North America the embargo lifts at 6:30pm ET Tuesday August 23, 2005.

Doctors should not reduce chemotherapy doses for obese women oestrogen-receptor negative* breast cancer, according to a research letter being published online today (Wednesday August 24, 2005) by THE LANCET.

Clinicians often reduce chemotherapy doses when treating obese patients because of concerns about altered drug disposition and toxicity in this group. However, little data are available to lend support to this policy. In this study, Marco Colleoni (European Institute of Oncology, Italy) and colleagues have found that reducing the first course of chemotherapy for obese patients with oestrogen-receptor negative breast cancer can be detrimental.

The researchers assessed the relation between BMI, chemotherapy dose reduction, oestrogen receptor expression, and outcome for premenopausal women with breast cancer by reviewing data from four randomised trials. They found that a higher proportion of obese patients (97 of 249) received less than 85% of protocol specified dose during the first course of chemotherapy compared with patients with normal and intermediate BMI. For obese patients who had oestrogen-receptor negative disease, those who received 85% or more of the first course dose had significantly better disease-free survival and overall survival than those who received less than 85%. However, obese patients with oestrogen-receptor positive breast cancer who had reduced doses of chemotherapy did not have a significant difference in their outcome compared to those given the recommended chemotherapy doses. The researchers also found that obese patients initially treated with protocol doses of chemotherapy did not have more toxicity than patients who received reduced doses.

Dr Marco Colleoni concludes: "Our findings suggest that for women with ER-absent or ER-low tumours, reduction in chemotherapy dose should be avoided."

In an accompanying comment Lars Holmberg (University Hospital, Uppsala, Sweden) states: "As with all interesting scientific investigations, the report raises several stimulating questions…Why is there an interaction with hormone receptor status? Does obesity modify the response to chemotherapy within the oestrogen-receptor-negative subset?…The only way to know more is if scientists find new and ingenious ways to address the intriguing hypotheses raised by Gelber's data."

Source: Eurekalert & others

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