Pre- and Post-diagnosis Physical Activity, Television Viewing, and Mortality Among Patients With Colorectal Cancer in the National Institutes of Health–AARP Diet and Health Study

SUMMARY:The American Cancer Society estimates that approximately 137,000 new cases of colorectal cancer were diagnosed in the United States in 2014 and over 50,000 died of the disease. Even though colon cancer localized to the bowel is potentially curable with surgery and adjuvant chemotherapy, advanced colon cancer is often incurable. Standard chemotherapy when combined with anti EGFR (Epidermal Growth Factor Receptor) targeted monoclonal antibodies such as VECTIBIX® (Panitumumab) and ERBITUX® (Cetuximab) as well as anti VEGF agent AVASTIN® (Bevacizumab), have demonstrated improvement in Progression Free Survival and Overall Survival. Reducing risk of death and improving survival even further with leisure time physical activity is the topic of this discussion. The most prevalent sedentary behavior, watching TV, has been associated with poorer survival in the general population. Several studies have suggested protective effects of physical activity on cancer recurrence although this has not been conclusive. Pooled data from other studies have shown that lack of physical activity among survivors of ColoRectal Cancer (CRC) has been associated with higher mortality risk. However, the independent effects of physical activity before and after colorectal cancer diagnosis, has remained unclear and the association between watching TV and mortality in survivors of CRC has not been defined. There are several biologic mechanisms that explain the association between sedentary life style, physical activity, and mortality. The adipose tissue in the body in addition to serving as the storage site for energy also releases adipokines, which have pro-inflammatory and anti-inflammatory properties. Physical activity decreases inflammatory adipocytokines and increases anti-inflammatory cytokines and thereby could affect cancer incidence and mortality. Also, physical activity has been shown to increase insulin sensitivity. Several studies have shown increased risk of CRC, increased angiogenesis, tumor growth, and anti-apoptotic activity with higher circulating insulin and insulin-like growth factor-1 and lower insulin-binding protein levels. Physical activity also improves cardiovascular health by lowering blood pressure. The authors in this study explored the impact of lifestyle such as moderate to vigorous intensity physical activity level and TV viewing time (sedentary life style) on ColoRectal Cancer mortality among CRC survivors, with particular attention to pre and post cancer diagnosis contributing factors. Data was collected from a large cohort of patients enrolled in the National Institutes of Health Diet and Health Study and the associations were analyzed between pre CRC diagnosis (N=3797) and post CRC diagnosis (N= 1759) life styles (physical activity and TV watching) and overall and disease-specific mortality. It was noted that patients who had 7 or more hours of weekly leisure physical activity before their diagnosis of CRC had a 20% lower risk of all-cause mortality compared to those who had a sedentary life style and were not engaged in any leisure time activity (HR=0.80; P=0.02). Patients who were engaged in 7 or more hours of weekly leisure physical activity post CRC diagnosis had a 31% lower risk of all-cause mortality compared to those who reported no activity (HR=0.69; P=0.006). This benefit was noted independent of pre-diagnosis activity. Amongst those who reported sedentary lifestyle, patients who spent 5 or more TV hours per day before CRC diagnosis had a 22% increased risk in all-cause mortality compared to those who watched no more than 2 hours of TV per day (HR=1.22; P=0.002). A similar trend of increased risk of all-cause mortality was seen in those who spent more TV hours, post diagnosis although this was not statistically significant. The authors concluded that in patients with CRC, leisure time physical activity was inversely associated with all-cause mortality, whereas more TV hours was associated with increased mortality risk. Health Care providers should therefore proactively promote increasing physical activity and minimizing TV hours, among survivors of ColoRectal Cancer. Arem H, Pfeiffer RM, Engels EA, et al. J Clin Oncol 2015; 33:180-188