June 28, 2017 | 5 minute read

Individuals diagnosed with cancer face unique health challenges such as treatment side effects and recurrence. Exercise can help, finds a large systematic review of the research.

The findings strengthen previous research on the benefits of exercise for cancer patients and survivors. It also supports the view that exercise is an important adjunct therapy in the management of cancer. The paper was published in Epidemiologic Reviews.

This latest review included 100 studies that evaluated exercise behavior following an adult’s cancer diagnosis. The studies all focused on exercise and cancer mortality, recurrence and/or adverse effects of cancer and its treatment. Review authors looked at epidemiological studies that followed survivors over time along with randomized controlled trials.

Exercise impacts cancer mortality and recurrence
This part of the review included 36 studies with over 68,000 participants on the impact of exercise on cancer mortality and recurrence. Two-thirds of the survivors had been diagnosed with breast cancer; almost all the others were survivors of prostate and colorectal cancers.

Key findings include:

• Patients diagnosed with cancer who were more physically active had a lower relative risk of breast cancer and colorectal cancer mortality. There was also a lower risk of cancer-specific mortality from a variety of cancer types.

• Overall, higher levels of exercise following a cancer diagnosis were associated with a 28%– 44% reduced risk of cancer-specific mortality.

• Higher levels of exercise following a diagnosis link to lower risk of cancer recurrence (21% – 35%), and a similar decreased risk of all-cause mortality.

• This study included data from 5 studies not included in any previous meta-analysis. The new data continues to support the findings of prior meta-analyses, reporting lower relative risk of cancer recurrence, cancer mortality, and all-cause mortality in people with breast and colorectal cancer who are more physically active.

Because the majority of these studies were epidemiological, it’s not possible to draw a direct cause-and-effect relationship between exercise and the improved outcomes, the paper notes. It’s possible that the observed protective effects of exercise may be due to the more active survivors having less advanced or aggressive tumors. Changes in other health behaviors and in reporting may also have affected the outcomes.

Exercise for Breast Cancer Survivors
Follow along with our exercise physiologist as she walks you through some simple stretches and exercise to help you get back into shape.

Exercise helps with fatigue, anxiety and stress  
For how exercise impacts treatment-related side effects, the paper reviewed 23 randomized controlled studies with exercise interventions that lasted between 4 weeks and 12 months. There were approximately 3,700 survivors included in these trials. The vast majority (85 percent) were women diagnosed with breast cancers.

For randomized control trials, studies looked at a series of treatment-related effects including bone health, cognitive function, sexuality, urinary incontinence and nausea.

This review also included 40 meta-analyses that covered 257 reported studies with over 9,000 patients. One-quarter of the studies focused on breast cancer; other cancer types included prostate, lung, colorectal and head and neck, among others.

For the review of meta-analyses, the studies looked at anxiety, depression, psychosocial distress, emotional well-being, mental health, stress, fatigue; lymphedema; physical function; physical health and quality of life.

Key findings include:

• There was particularly strong evidence that exercise helps with fatigue. As pointed out in the study, this is consistent with the National Comprehensive Cancer Network guidelines for managing fatigue, which recommends exercise as the top approach for managing cancer-related fatigue.

• There was also strong evidence that exercise helps survivors with distress, anxiety, depression, stress, emotional well-being, and mental health issues that survivors may experience.

• For physical function, sleep, body image, and physical health, the evidence was not as strong as for fatigue or psychosocial issues, but the majority of the analyses concluded that exercise linked to a positive effect.

Every site other than breast cancer is understudied, the paper notes. Yet in the absence of significant risk, there is enough evidence to show that exercise is valuable for general health. It can do more harm than good to wait for further research to prescribe exercise, the authors write.

Another recent study looking at exercise and cancer focused on mechanisms.

How exercise influences cancer progression  
AICR research shows that exercise lower the risk of developing colorectal, endometrial and breast cancers. There are many mechanisms by which exercise lower risk of these cancers and can help cancer patients, according to another systematic review published earlier this year.

The paper, published in the British Journal of Sports Medicine, reviewed 168 papers that investigated biochemical pathways of exercise related to cancer. The authors categorized the papers into direct and indirect pathways, noting there is overlap between them.

The indirect effects included changes in vitamin D, weight reduction, sunlight exposure and improved mood. The authors note that excess sunlight is a cause of skin cancer.

The direct effects included insulin-like growth factor, epigenetic effects on gene expression and DNA repair, antioxidant pathways, chronic inflammation and prostaglandins, energy metabolism and insulin resistance.

There are likely other pathways yet to be investigated, the authors note. And it remains unclear which of these mechanism has the most important role. Yet what this summary does show is that there is clear biological evidence for the cancer-related health benefits of exercise. While more research is needed, this paper can motivate cancer patients and survivors to engage in exercise programs.

Sources:

The Impact of Exercise on Cancer Mortality, Recurrence, and Treatment-Related Adverse Effects. Cormie P, Zopf EM, Zhang X, Schmitz KH.
Epidemiol Rev (2017) 39 (1): 71-92. Published: 27 April 2017.

Thomas RJ, Kenfield SA, Jimenez A. Exercise-induced biochemical changes and their potential influence on cancer: a scientific review. Br J Sports Med 2017;51:640-644.