Measures of physical function clarify the prognostic blur of cancer survivorship

Extract

Physical functioning and efficient mobility have been a primary emphasis of natural selection throughout human evolution (1). Physical function, such as walking, is a complex activity that requires a year to develop after birth (2). Multiple physiologic networks, such as the cardiopulmonary, neurologic, and musculoskeletal systems, work together to enable optimal physical function (3). Moreover, these physiologic networks are redundant, so other systems can compensate when one physiologic system is compromised (3). Functional declines occur when these physiologic networks become depleted and compensatory systems fail (4). In the first year after cancer diagnosis, cancer survivors experience accelerated declines in physical function relative to individuals without cancer (5). It is uncertain, however, if these functional declines after cancer diagnosis relate to survival.

In this issue of the Journal, Dr Gonzalo-Encabo and colleagues (6) report how declines in physical function after a cancer diagnosis are associated with all-cause and cancer-specific death. The investigators leveraged data from more than 8000 postmenopausal women who were enrolled in the Women’s Health Initiative and diagnosed with any type of cancer. Physical function was measured using the 36-item Short Form Health Survey (SF-36) before and within 1 year after cancer diagnosis. The SF-36 inquiries about the difficulty of completing 10 tasks, such as walking one-quarter mile or climbing 10 stairs, forming a score that ranges from zero to 100, with higher scores indicating better physical function. The primary outcomes were the time to death from any cause and death attributed to cancer. Important demographic, behavioral, and clinical characteristics were included in multivariable regression models; a subset of participants had detailed cancer treatment data available and were examined in an exploratory analysis. During a median follow-up of 7.7 years, 3316 participants died from all causes (41.1% of the analytic sample).