Physical activity is emerging from epidemiologic research as a lifestyle factor that may improve survival from colorectal, breast, and prostate cancers. However, there is considerably less evidence relating physical activity to cancer recurrence and the biologic mechanisms underlying this association remain unclear. Cancer patients are surviving longer than ever before, and fear of cancer recurrence is an important concern. Herein, we provide an overview of the current epidemiologic evidence relating physical activity to cancer recurrence. We review the biologic mechanisms most commonly researched in the context of physical activity and cancer outcomes, and, using the example of colorectal cancer, we explore hypothesized mechanisms through which physical activity might intervene in the colorectal recurrence pathway. Our review highlights the importance of considering pre-diagnosis and post-diagnosis activity, as well as cancer stage and timing of recurrence, in epidemiologic studies. In addition, more epidemiologic research is needed with cancer recurrence as a consistently defined outcome studied separately from survival. Future mechanistic research using randomized controlled trials, specifically those demonstrating the exercise responsiveness of hypothesized mechanisms in early stages of carcinogenesis, are needed to inform recommendations about when to exercise and to anticipate additive or synergistic effects with other preventive behaviors or treatments.
Journal of molecular medicine (Berlin, Germany). 2017 Jun 15 [Epub ahead of print]
Christine M Friedenreich, Eileen Shaw, Heather K Neilson, Darren R Brenner
Department of Cancer Epidemiology and Prevention Research, CancerControl Alberta, Alberta Health Services, 2210 2nd St SW, Calgary, AB, T2S 3C3, Canada. ., Department of Cancer Epidemiology and Prevention Research, CancerControl Alberta, Alberta Health Services, 2210 2nd St SW, Calgary, AB, T2S 3C3, Canada.