This prospective cohort study of consecutive elderly cancer patients was undertaken to evaluate the role of the multidimensional geriatric assessment (MGA) as an aid in treatment decision-making. A total of 571 cancer patients (aged > or =70) were enrolled during 6-year (1999-2005). All underwent MGA as part of the first evaluation. In multivariate analysis, the probability of receiving active, instead of palliative, treatment was negatively associated with increasing age (odds ratio=0.69 every 5 years, p=0.005), living alone (OR=0.54, p=0.031), dependence in activities of daily living (ADL score >0, OR=0.41, p=0.003) and a low body-mass index (BMI) (OR=0.51, p=0.061); while a positive association emerged for instrumental activities of daily living (IADL) score (OR=1.12 per point, p=0.019). Our data suggest that MGA, in addition to age, is a useful tool in clinical practice for deciding cancer treatment in elderly patients, with a major independent role played by living alone, ADL, IADL and BMI.