Chen said additional research will be needed to explain these differences in outcomes for patients with head and neck cancers. One theory suggests that smoking deprives the body of much-needed oxygen. "Radiation therapy requires oxygenation for the production of free radicals, which attack cancer cells," he said.

Chen emphasized that his findings are based on an observational study, which does not establish a cause-effect relationship between smoking during radiation therapy and poorer outcomes. Researchers were unable to determine with certainty the actual cause of death of each patient, and active smokers may be at higher risk of death from other medical problems such as heart disease, stroke and diabetes.

"In addition, patients unable to quit may also have non-cancer-related medical and psychosocial problems that could possibly contribute to inferior survival," Chen said. "Those who continue to smoke even after a diagnosis of head and neck cancer are likely to be at higher risk for alcohol abuse, have less social support and have lifestyles associated with high-risk health behaviors."

Chen stressed that the findings still are instructive for clinicians.

"Regardless of the underlying reasons, our finding should provide both clinicians and patients alike with compelling evidence supporting the role of smoking cessation in this setting" he concluded. "Counseling these patients on its importance, both here at UC Davis and in the community, is a must."

Source: University of California - Davis - Health System