Exercise May Extend Survival in Metastatic Colon Cancer Progression, survival hazards improved with moderate activitiy

Patients who engaged in at least 5 hours of non-vigorous physical activity a week had a 25% reduction in the hazard for survival. With 4 or more hours of weekly activity, the survival hazard improved by 20%. As little as 30 minutes of daily activity reduced the risk of disease progression and death. The findings are particularly noteworthy because the activity level evaluated in the study did not set the bar unrealistically high for patients with metastatic colorectal cancer, Other studies showed that the risk of developing colorectal cancer decreases as physical activity increases. Similar data have been reported for other types of cancer. I do not see where the how/why it helps. http://www.medpagetoday.com/MeetingCoverage/MGICS/62582?xid=nl_mpt_DHE_2017-01-18&eun=g721819d0r&pos=2