Despite California’s success in tobacco control efforts in recent years, nearly half the deaths from 12 different cancer types were linked to tobacco use, according to a new study from researchers with the Comprehensive Cancer Center at University of California, Davis.

“This is almost double what was previously estimated in a study that looked at 2014 data,” said epidemiologist Frances Maguire, PhD, MPH a California Cancer Registry and UC Davis researcher and the lead author of the study, in a UC Davis news release. “However, we believe this is a more accurate representation, since tobacco use data came directly from individual patients with cancer rather than estimates based on general population surveys. This study is also specific to the 12 tobacco-related cancers.”

Published in JAMA Network Open, the study used data collected from the California Cancer Registry, a cancer surveillance system managed by UC Davis, to analyze people diagnosed with one of 12 tobacco-related cancers from 2014 to 2019. The tobacco-related cancers considered in the study were: oral cavity or pharynx, larynx, esophagus, lung, liver, stomach, pancreas, kidney, bladder, colon or rectum, cervix, and acute myeloid leukemia.

From 2017 to 2019, researchers found that about half of cancer deaths—93,764 people—were associated with tobacco use, including cigarettes; other smoked tobacco products, including pipes and cigars; and smokeless tobacco products, such as chewing tobacco or snuff. The registry does not yet collect Information on vaping products.

Of the nearly 400,000 patients diagnosed with a tobacco-related cancer from 2014 to 2019, nearly three quarters were over 60 years old, more than 57% were non-Hispanic white men and about 46% had lung or colorectal cancers.

For men and women, lung and bladder cancer accounted for the greatest number of deaths related to tobacco. The largest proportions of tobacco-related cancer deaths were found in lung (90.2%), larynx (85.6%), esophagus (58%), oral cavity/pharynx (55.5%), and bladder (52.7%).

“Smoking remains the largest preventable cause of death from cancer and other diseases,” said study coauthor and UC Davis researcher Theresa Keegan, PhD. “This study shows that tobacco continues to kill Californians with cancer at an alarming rate.”

About 57% of Californians in the study reported using tobacco at some point, and 69,103 patients (17.5%) reported current tobacco use, which was higher than the general population (11%).

California has seen a decline in the proportion of deaths due to smoking. Notably, there was a 48% decline from 2014 to 2016, followed by a 45% drop from 2017 to 2019. What’s more, the overall number of cancer deaths attributed to smoking decreased by about 10%.

Researchers believe the changes seen during these two time periods could suggest promising trends in tobacco use among Californians with cancer. In recent years, the state implemented ongoing tobacco control efforts, such as introducing a tobacco tax of $2 per pack in 2016.

“Current tobacco use among the people diagnosed with cancer was higher than among the general population but decreased over time,” Maguire said. “This suggests that tobacco control efforts have contributed to a decline in cancer mortality in California, but smoking cessation efforts targeted at patients with cancer are needed.” 

Fellow cancer researcher and internist Elisa Tong, MD, added, “It’s important to remember that it’s never too late to quit smoking even after a cancer diagnosis because quitting can improve cancer treatment outcomes and significantly reduce mortality.”

For related news, see the feature “What Are Pack-Years?” to learn how that phrase is used in understanding smoking history and lung cancer.