A new report published by Canadian researchers in the journal Cancer suggests that cancer patients may get a boost to their immune system from regular exercise. However, they caution that more research is needed to see if this translates into a reduced risk of recurrence.

The researchers, led by Adrian Fairey and colleagues from the University of Edmonton, reviewed six published studies on the relationship between exercise and cancer. They noted that four of the studies indicated that patients who exercised during or after cancer treatment had a measurable boost in their immune system function. However, they challenged how the studies were designed, saying that no definitive conclusions could be drawn as a result.

"Overall, four out of six studies reported statistically significant improvements in a number of cancer-related immune system components as a result of exercise," they wrote. "However, there are several limitations that must be considered when interpreting the findings of these studies." They specifically cited the sample sizes, designs, physical exercise interventions, physical fitness assessments, and immunological assessments.

"Additional research is needed to determine if physical exercise in cancer survivors may reduce the risk of cancer recurrence and secondary malignancies and increase survival times," they wrote.

However, their conclusions run counter to a growing body of evidence that improving overall health-through exercise, diet and other lifestyle factors-has a beneficial impact not only against cancer, but as a risk reducer for a wide variety of chronic ailments.

In fact, an earlier study published in the journal Cancer specifically cited physical activity in postmenopausal women as a significant factor for reducing breast cancer risk. A team of Dutch researchers led by Miranda J. M. Dirx, M.Sc., from the Department of Epidemiology at Maastricht University in The Netherlands found that walking or biking for more than 90 minutes per day may reduce the risk for breast cancer by as much as 24 percent.

Their study was conducted as part of the Netherlands Cohort Study, an ongoing study on the association between an individual's diet and likelihood of developing cancer. It involved 62,537 women aged 55-69.

"The study findings support the hypothesis that recreational physical activity is associated inversely with breast carcinoma risk," they wrote. "Physical activity is one of the few modifiable, protective factors for breast carcinoma, and there are many other important health-related reasons to promote regular exercise."

SOURCES:
Cancer, January 18, 2002; 94(2): 539-551
Cancer, September 15, 2001; 92(6): 1638-1649