Relation between chemotherapy dose, oestrogen receptor expression, and body-mass index

SummaryClinicians often reduce chemotherapy doses when treating obese patients because of concerns about overdosing. We assessed dose-response according to body-mass index (BMI) and oestrogen receptor (ER) expression of the primary tumour in premenopausal patients with node-positive breast cancer treated with classical CMF (cyclophosphamide, methotrexate, and 5-fluorouracil). Obese patients were significantly more likely to receive a lower chemotherapy dose (<85% of expected dose) for the first course than were those with normal or intermediate BMI (39% vs 16%, p<0·0001). For obese patients and for the total population, reducing the dose of chemotherapy was associated with a significantly worse outcome for the ER-negative cohort (total population hazards ratio ⩾85% vs