Women who survive breast cancer may suffer from limited function that affects motion, strength and dexterity, which may adversely affect all-cause and competing-cause survival, but not breast cancer survival.
Breast cancer survivors who have functional limitations are at the same risk of dying from a recurrence of breast cancer as physically fit survivors, but are more likely to die from other causes.
Breast cancer survivorship is increasing due to improvements in early detection and adjuvant therapy, especially in industrialized countries. Since overall survival is the most therapeutically relevant outcome for cancer patients, little attention has been given to the physical limitations and other health problems that affect particularly older women who have had breast cancer.
Although these problems have been associated with poor treatment tolerance, it is unclear whether these limitations affect risk of death from breast cancer or other competing causes.
To determine how physical limitations following initial breast cancer treatment affect morbidity and mortality among women who have had breast cancer, Dejana Braithwaite, Ph.D., of the University of California, San Francisco, and colleagues, studied 2,202 women with breast cancer in the Life After Cancer Epidemiology cohort, who were followed for up to 11 years after diagnosis. They looked at the impact of functional limitations on survival as a function of age, body mass index, tumor stage, and other lifestyle characteristics.
The researchers found that 39 percent of the participants reported at least one limitation following initial adjuvant treatment. They write, "The pattern of the relationships between functional limitations and survival supports the view that functional limitations have prognostic value for breast cancer independently of known prognostic factors, including co-morbidity."
While older and overweight women reportedly had more functional limitations than other women, the impact on survival was not statistically significant.
However, outcomes differed according to disease stage: physical limitation had a stronger effect on survival among women with localized disease than among those with advanced-stage disease. Although this seems counter-intuitive, it may reflect the finding that women with functional limitations have poorer treatment tolerance because they are more likely to be older, less physically active, and overweight or obese.
The results make "biological and clinical sense," according to the authors, because the functional limitations that affect survival "…may reflect chronic inflammation and commensurately diminished function of vital organs or systems."
A limitation of the study is the lack of a control group of women without breast cancer, so the researchers could not determine whether the increase in mortality due to functional limitations was higher in women with breast cancer than in their counterparts without the disease.
In an accompanying editorial, Harvey Jay Cohen, M.D., of the Center for the Study of Aging and Human Development at Duke University, writes that the study's conclusions could be incorporated into cancer survivorship plans, especially for elderly survivors. Since "the main impact of functional limitations is on non-cancer causes of death," Cohen writes, "Such an evaluation could guide therapy regarding underlying co-morbidities and other reasons for functional decline, such as obesity and decreased physical activity."
Cohen also writes that the study importantly "suggests that implementing known interventions such as disease screening, chronic disease management, and diet and exercise programs for cancer survivors can have substantial impact."