Constructs of burden of illness in older patients with breast cancer: a comparison of measurement methods

The burden of illness can influence treatment decisions, but there are limited data comparing the performance of different illness burden measures. We assessed the correlations between five previously validated measures of illness burden and global health and physical function and evaluated how each measure correlates with breast cancer treatment patterns in older women.

A cohort of 718 women > 67 years with early-stage breast cancer formed the study group. STUDY DESIGN/DATA COLLECTION METHODS: The study made a cross-sectional comparison of illness burden measures (Charlson index, Index of Co-existent Diseases, cardiopulmonary burden of illness, patient-specific life expectancy, and disease counts) and physical function and self-rated global health status. Data were collected from records and patient interviews.

All of the measures were significantly correlated with each other and with physical function and self-rated health (p < .001). After controlling for age and stage, life expectancy had the largest effect on surgical treatment, followed by self-rated physical function and health; life expectancy was also independent of physical function. For instance, women with higher life expectancy and better self-rated physical function and health were more likely to receive breast conservation and radiation than sicker women. Women with higher physical functioning were more likely to receive adjuvant chemotherapy than women with lower functioning.

Several measures of illness burden were associated with breast cancer therapy, but each measure accounted for only a small amount of variance in treatment patterns. Future work is needed to develop and validate measures of burden of illness that are feasible, comprehensive, and relevant for diverse clinical and health services objectives.