Exercise Benefits Cancer Survival

January 2008 - Dr Michael F. Leitzmann, of the National Cancer Institute, Bethesda, Maryland and colleagues analyzed the results of two questionnaires on physical activity from 252 925 participants (142 828 men and 110 097 women). During five years of follow-up, 7900 died. Compared with being inactive, individuals who performed the amount of vigorous physical activity recommended in national guidelines (at least 20 minutes three times per week) were 32 per cent less likely to die while those who performed moderate physical activity (at least 30 minutes most days of the week) were 27 per cent less likely to die. Smaller amounts of physical activity also appeared to be associated with a 19 per cent reduced risk of death. The study was published in the Archives of Internal Medicine.

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March 2007 - Two studies have investigated the role of exercise in breast cancer risk, treatment and rehabilitation.

A new report by Scottish researchers published in the British Medical Journal has found that group exercise can help to improve the physical and psychological wellbeing of people diagnosed with breast cancer, the most common form of the disease in women in the UK. Rigorous standard treatments such as chemotherapy and radiotherapy can have a big impact on quality of life but rehabilitation programmes tend to focus on psychotherapy or social support rather than physical consequences.

Researchers investigated whether group exercise programmes proved beneficial to women undergoing treatment for early stage breast cancer. Over 200 women were split into two groups: the control group received standard care; the second group was also invited to participate in a 12 week exercise programme, comprising two classes led by trained specialists and an additional home session.

On completion, researchers assessed participants' physical and psychological wellbeing by measuring factors such as levels of depression, quality of life, mood, shoulder mobility, walking distances and weekly levels of physical activity. Follow-up measurements were made six months later.

The study found that participants in the exercise group had better outcomes on both physical and psychological levels at the 12 week and six month assessments, having made fewer visits to their GP and spent fewer nights in hospital. Researchers comment that these benefits may be a result of the exercise itself or the group experience, or a combination of both. They conclude that clinicians should encourage activity during cancer treatment, and policy makers should consider including opportunities for exercise in rehabilitation programmes.

The second study, by researchers from the University of Wisconsin Paul P. Carbone Comprehensive Cancer Center (UWCCC) and published in Cancer Epidemiology Biomarkers & Prevention found that a minimum of six hours per week of strenuous physical activity may reduce the risk of invasive breast cancer by 23 per cent. The survey of over 15 000 women demonstrated a lifetime protective effect.

Researchers conducted a population-based case control study of women between the ages of 20 and 69 in Massachusetts, New Hampshire, and Wisconsin. Using structured telephone interviews, researchers questioned 7630 women without breast cancer, 1689 survivors of in situ or non-invasive breast cancer and 6391 survivors of invasive breast cancer about physical activity, occupation, family history of breast cancer, menopausal status, and body mass index. They found that women with no family history of breast cancer who exercised had a reduced risk of developing invasive breast cancer whether the physical activity took place early or late in life, pre or post-menopause.

In seeking mechanisms, researchers highlight previous research linking high levels of estrogen to increased risk for developing breast cancer. Women who exercised extensively tended to be older at the time of their first period and to have irregular menstrual cycles, thus a shortened estrogen-producing phase and lower body exposure to the hormone. Similarly, physically active postmenopausal women have been shown to have lower estrogen levels. Researchers suggest this may explain why increased physical activity reduces the risk of breast cancer. Other potential mechanisms include prevention of weight gain, regulation of insulin sensitivity and alterations in immune function.

Amy Trentham-Dietz assistant professor at the University of Wisconsin-Madison said:

"Intervention studies assessing the effect of physical activity on estrogen and other hormone exposure, and other biomarkers of risk would provide valuable insights on the mechanisms of physical activity in reducing breast cancer risk. Further studies of population subgroups are necessary to gain a better understanding of the relation of physical activity to breast cancer risk, and to identify the groups most likely to gain benefit from it. Future research should also consider household activity in addition to recreational and occupational activities."

Brian Sprague, a UWCCC research assistant and lead author commented:

"A woman's hormone levels naturally fluctuate throughout her life, and we have found that exercise likely offers protection against breast cancer regardless of a woman's stage in life. The take-home message for women should be that it is never too late to begin exercising."

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