Decline in physical functioning in first 2 years after breast cancer diagnosis predicts 10-year survival in older women

Breast cancer patients often experience a decline in physical functioning following cancer diagnosis. Although most patients recover after treatment, some patients do not. These changes may be magnified in older women with comorbid conditions and could impact survival outcomes. We used longitudinal data from a prospective cohort study of women 65+ years of age, recruited shortly after diagnosis of early stage breast cancer, to examine changes in self-reported physical functioning measured with the Physical Function Index (PF-10) of the Medical Outcomes Study Short Form-36. Outcomes were constructed for small (0.2 SD), medium (0.5 SD), and large (0.8 SD) declines in the PF-10 measurement over two intervals: (1) 3 to 15 months following cancer diagnosis, encompassing treatment and early recovery, and (2) 3 to 27 months following cancer diagnosis, in order to detect sustained recovery versus persistent decline. Cox-proportional hazards regression was used to examine association between survival and decline in PF-10 scores. A large (> 0.8 SD) decline in PF-10 scores from 3 to 27 months predicted shorter 10-year survival (hazard ratio = 1.34, 95 % confidence interval 1.1-1.6). Persistent decline at 27 months was associated with less education, higher baseline PF-10, increased comorbidity, and higher body mass index. Older women with breast cancer who experience a large and persistent decline in PF-10 are at increased mortality risk. Future research should examine the value of clinical assessment of physical function as a marker for mortality and test interventions to prevent decline in physical function to improve post-treatment survival outcomes. Many breast cancer survivors experience a decline in physical functioning in the year following their cancer diagnosis. While the majority of patients recover in the year after treatment is completed, individuals who experience a persistent decline in physical functioning without recovery are at risk of functional decline and early mortality. Our results highlight the importance of assessing functional status to identify those at risk for functional decline, and suggest a potential role for early intervention in these individuals.