Risk factors for unplanned discontinuation of scheduled treatment in elderly patients with castration-resistant prostate cancer: results of the IBuTu study. 
To gain knowledge about the factors associated with discontinuation of scheduled treatment in elderly men with castration-resistant prostate cancer (CRPC).  Patients ≥ 70 years with CRPC starting a new line of treatment were included in a prospective cohort study.  A geriatric assessment (CGA) was performed at baseline, including comorbidity, mobility, functional/mental/nutritional status, as well as depression.  Furthermore, pain intensity, quality of life, ECOG-performance status, and physicians' and patients' perception of health were documented.  Reasons for and factors associated with discontinuation of scheduled treatment were analysed by univariate and multivariate analysis.  After inclusion of 177 of 300 planned patients, the study was closed due to slow recruitment.  160 patients were eligible for final analysis.  Median age was 77.5 years.  46% received chemotherapy, and 54% hormonal treatment.  Discontinuation of scheduled treatment occurred in 91 patients (57.6%).  The main reasons were progressive disease/death in 63%, adverse events/toxicity in 22%, and withdrawal of consent in 8%.  In bivariate analyses, factors associated with discontinuation of treatment were age ≥ 80 years, ECOG PS ≥ 2, compromised/poor health status (physicians'/patients' assessment), and compromised functional or nutritional status.  In multivariate analysis, the only remaining factor independently associated with discontinuation of scheduled treatment was impairment of activities of daily living (ADL < 100 points) (OR = 4.2 for discontinuation; p < 0.05).  Despite limitations due to early termination of the study, our results demonstrate that discontinuation of scheduled treatment was common, and that compromised ADL seems to be a significant risk factor for treatment failure in elderly patients with CRPC.