Compared with men who did not smoke after a cancer diagnosis, those who smoked after diagnosis had a 59 percent increase in risk of death from all causes, after adjusting for factors including age, cancer site, and treatment type. When limited to men who were smokers at diagnosis, those who continued smoking after diagnosis had a 76 percent increase in risk of death from all causes compared with those who quit smoking after a diagnosis.
"Many cancer patients and their health care providers assume that it is not worth the effort to stop smoking at a time when the damage from smoking has already been done, considering these patients have been diagnosed with cancer," said Li Tao, M.D., M.S., Ph.D., epidemiologist at the Cancer Prevention Institute of California in Fremont. "Our study provides evidence of the impact of postdiagnosis smoking on survival after cancer, and assists in addressing the critical issue of tobacco control in cancer survivorship."
When cancer patients who continued smoking after diagnosis were compared with cancer patients who quit smoking after diagnosis, the risk of death varied with different cancer organ sites: risk of death increased by 2.95-fold for bladder cancer patients who continued smoking, 2.36-fold for lung cancer patients who continued smoking, and 2.31-fold for colorectal cancer patients who continued smoking.
"As far as we know, only a fraction of cancer patients who are smokers at diagnosis receive formal smoking cessation counseling from their physicians or health care providers at the time of diagnosis and treatment, and less than half of these patients eventually quit smoking after the diagnosis," Tao said. "Therefore, there is considerable room for improvement with regard to tobacco control in the postdiagnosis setting for the growing population of cancer survivors.
"Compared with the general population, cancer patients are more likely to receive treatment on an inpatient basis or prolonged outpatient visits," she added. "Health care providers have an important 'window of teachable moment' to engage in tobacco-use counseling during these visits. This piece of solid evidence from our study in establishing the role of cigarette smoking in cancer survival is necessary for implementing and enforcing smoking cessation interventions in order for patients to increase their chances to achieve better outcomes. Policymakers should consider including information on health outcomes of smoking cessation in educational materials for specific intervention programs and policies targeting cancer survivors."
Tao and colleagues used data from the Shanghai Cohort Study, which is a prospective cohort study investigating the association between lifestyle characteristics and risk of cancer among middle-aged and older men in Shanghai, China. Between 1986 and 1989, 18,244 men were enrolled in the study. Participants were 45 to 64 years old, and completed an in-person interview-based questionnaire about demographics, history of tobacco and alcohol use, diet, and medical history. Data were updated on an annual basis for all surviving cohort members.
By 2010, 3,310 participants were diagnosed with cancer. Of these participants, 1,632 were eligible for this study. Of the eligible study participants, 931 died from any cause. In addition, 340 were nonsmokers, 545 quit smoking before a cancer diagnosis, and 747 were smokers at diagnosis.
Of the 747 smokers at diagnosis, 214 quit after diagnosis, 197 continued smoking consistently, and the remaining 336 smoked intermittently.