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ASCO advises chemo dosing based on actual body weight

NEW YORK (Reuters Health) – A guideline issued by the American Society of Clinical Oncology recommends that cytotoxic chemotherapy be dosed according to obese patients’ actual weight instead of their adjusted ideal body weight.

“With the incidence of obesity at an all-time high in the United States, as well as in other developed and developing nations, oncologists face this issue more than ever before,” said Dr. Jennifer Griggs, of the University of Michigan and co-chair of the ASCO guideline Expert Panel, in an ASCO statement.

The guideline was published online April 2 in the Journal of Clinical Oncology. The authors note that practice pattern studies indicate that up to 40% of obese patients (i.e., with a body mass index of 30 or more) receive chemo doses that are not based on actual body weight, because of concerns about side effects or overdosing.

“But for obese patients to fully benefit from today’s effective therapies, they need to receive the full, appropriate dose of these medicines,” said Dr. Griggs.

In a systematic literature review, the panel could not find any randomized studies comparing dose selection based on full body weight vs any other method of calculating dosage. The guideline is therefore based on evidence derived from subgroup analyses and registry data.

The review found no evidence of increased toxicity among obese patients receiving full-weight chemo doses. In fact, myelosuppression in this setting may be less severe than in non-obese patients.

Furthermore, based on the available data, “it seems likely that the same principles regarding dose selection for obese patients apply to the morbidly obese,” the authors add.

The authors also concluded that if high-grade toxicity occurs, obese patients should be managed with the same guideline-based dosage reductions as any other patient, since there is no evidence that greater dose reductions are necessary for them.

With certain agents, the maximum dose shouldn’t exceed established dosing limits because of the risk of severe toxicity. These include vincristine, for example, because of its neurotoxic potential, and bleomycin, because of the risk of lung scarring

“This guideline should ease fears about administering chemotherapy based on actual body weight to otherwise healthy obese patients with cancer,” said co-chair Dr. Gary H. Lyman, with the Duke Cancer Institutes, in the ASCO statement.

“While a chemotherapy dose for an obese patient may be larger than some physicians are accustomed to, they can rest assured that the risk of toxicity associated with chemotherapy dosing based on actual body weight is no greater in obese patients than in non-obese patients with cancer,” he concluded.

SOURCE: http://bit.ly/HlF4Ln

J Clin Oncol 2012.