About 49,000 cases of breast cancer and 43,000 colon cancer cases yearly in the United States are linked to a lack of physical activity, researchers say. Senior epidemiologist Christine Friedenreich of Alberta Health Services-Cancer Care in Canada said the latest results from the Alberta Physical Activity and Breast Cancer Prevention Trial involve C-reactive protein, a marker of inflammation, which is linked to cancer risk. The study, published in the journal Cancer Prevention Research, found moderate-to-vigorous daily activity reduced C-reactive protein levels among post-menopausal women. Although researchers have not yet identified how inflammation increases cancer risk, it is known that the inflammation process produces cytokines -- immune-response chemicals that encourage cell proliferation and suppress cell death -- that contribute to increased cancer risk. \"In breast and colon cancers, for example, we\'re seeing overall risk reductions of about 25 percent to 30 percent associated with higher levels of physical activity. With prostate cancer the evidence isn\'t as strong but it\'s still there -- about 10 percent to 20 percent lower risk. For endometrial cancer, we are finding about 30 percent to 35 percent risk reduction with more physical activity,\" Friedenreich said in a statement. \"These numbers are powerful. The bottom line: For many of the most common cancers, it seems like something as simple as a brisk walk for 30 minutes a day can help reduce cancer risk.\" The findings were also presented in the American Institute for Cancer Research annual research conference on in Washington.