Being physically active might lengthen the lives of people with breast and colon cancer, a new study suggests.
Exercise may also benefit patients with other cancers, but there is no substantial evidence to make that claim, the researchers added.
"We have lots of data that says physical activity after a cancer diagnosis is generally safe and is associated with many improvements in overall quality of life, and these data suggest that it may even be beneficial in terms of prolonging life," said lead researcher Dr Rachel Ballard-Barbash, associate director of the applied research programme in the division of cancer control and population science at the US National Cancer Institute.
"For many years, we have tended to think of a diagnosis of cancer being fatal, but as we are diagnosing people much earlier and receiving effective treatment, they're living for a long time with their cancer," she said.
Cancer is becoming more of a chronic disease, Ballard-Barbash explained.
"Because of that, many people actually are at risk for other chronic diseases, like heart disease, diabetes and hypertension, and physical activity is well known to be beneficial for these conditions," she added. The report was published in the Journal of the National Cancer Institute.
How the study was done
For the study, Ballard-Barbash's team analyzed 27 observational studies published between January 1950 and August 2011 that looked at cancer survival and physical activity.
The evidence of these benefits was strongest for breast cancer patients, where exercise significantly reduced death from all causes including breast cancer, the researchers found. Strong data also existed for improved survival among colon cancer patients.
The researchers also looked at other randomised controlled studies that suggested exercise benefited patients in a variety of ways, including improving insulin levels, reducing inflammation and possibly improving the body's immune system.
Dr Edward Giovannucci, a professor of nutrition and epidemiology at the Harvard School of Public Health and author of an accompanying journal editorial, said that "even though direct cancer effects of physical activity are not definitively proven, given that physical activity is generally safe, improves quality of life for cancer patients and has numerous other health benefits, adequate physical activity should be a standard part of cancer care."
"The vast majority of cancer patients will likely benefit to some degree from physical activity," he added.
Exercise and cancer
Few factors have shown as much promise in extending the lives of cancer survivors, Giovannucci wrote.
"Many treatments may increase survival, but at a cost of quality of life; physical activity may not only extend life but also enhances its quality," he added.
Samantha Heller, a dietitian, nutritionist, exercise physiologist and clinical nutrition coordinator of the Center for Cancer Care at Griffin Hospital, in Derby, Conn., said that "we have evidence to suggest that physical activity not only improves survival of people living with cancer, but it also decreases the risk of many other chronic diseases."
"Conversely, physical inactivity has been associated with many cancers including breast, colon, prostate, pancreas and melanoma," she said.
Because of certain chemotherapy and radiation therapy treatments for cancer, survivors may be at an increased risk of additional cancers and chronic diseases such as cardiovascular disease, Heller said.
"Therefore, a healthy lifestyle including regular exercise and a healthy diet is essential for survivors to reduce the risk of cancer recurrences and other diseases," she said.
Regular physical activity also improves sleep, psychological and emotional well-being and helps manage stress, Heller said.
"The number of cancer survivors is, happily, growing in the U.S.," she said. "We need to get the word out to them that exercise, whether it is walking, dancing, running, swimming or hula hooping, will boost their health, fitness level and quality of life."
Living with cancer
For more about exercise and cancer, visit the U.S. National Cancer Institute.
(Copyright © 2012 HealthDay. All rights reserved.)