New research published in the Journal of Clinical Oncology finds that cigarette smoking among colorectal cancer survivors is tied to more than twice the risk of death compared to not smoking.
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.
Estimates from the ACS for 2014 show that nearly 137,000 Americans were diagnosed with colorectal cancer, and over 50,300 died of the disease, which is the third leading cause of cancer death in the US.
In the US, early detection and prevention of colorectal cancer is possible because more and more people have access to screening tests.
Increased use of colonoscopy to screen the over-50s in the US is thought to have led to a decline in colorectal incidence and deaths in this age group in the past 10 years.
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.
The study is one of the largest to look at links between smoking and colorectal cancer survival and is thought to be the first that determines patients’ smoking status before and after diagnosis.
The researchers, led by Dr. Peter T. Campbell, a cancer epidemiologist and director of the ACS Tumor Repository, analyzed the link between smoking – before and after diagnosis – with death due to all causes and colorectal cancer specifically.
The data they used came from a pool of 184,000 adults taking part in the American Cancer Society’s Cancer Prevention Study II, among whom they identified 2,548 people newly diagnosed with invasive, non-metastatic colorectal cancer.
From this group of colorectal cancer survivors, over an average 7.5-year follow-up, 1,074 died, including 453 as a result of their cancer.
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.
Those who were classed as former smokers before diagnosis had a higher risk of death from all causes, but not 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.
In November 2014, Medical News Today reported a study that found in the US colorectal cancer rates are rising among young adults. The researchers found while rates are falling among the over-50s, they have risen among Americans aged 20-49. Colorectal cancer screening in the US is recommended for everyone aged 50 and over.