The American Cancer Society (ACS) researchers say their findings add to increasing evidence of links between smoking and higher risk of death due to any cause and colorectal cancer in particular. The ACS team carried out the new study because while there is plenty of evidence tying smoking to a higher risk of colorectal cancer, the link with survival after diagnosis is less well-known. When they analyzed the data, the team found colorectal survivors who were smokers before diagnosis had twice the risk of death from all causes, as well as from colorectal cancer specifically. Smoking after diagnosis was also linked to twice the risk of death from any cause, and nearly twice the risk of death from colorectal cancer specifically. While the study did not look at the mechanisms underlying these strong links, the researchers speculate that perhaps smokers have more aggressive tumors, or that smoking may weaken or interfere with cancer treatment. They say further studies should now look into what biological reasons there might be to explain the link between smoking and raised risk of death from colorectal cancer among survivors, and also whether quitting smoking after diagnosis reduces this risk.