Source: www.rtmagazine.com
Author: staff

Assuming that total exposure is the same, it is worse to smoke lightly for many years than to smoke heavily for a few years when it comes to the risk of head and neck cancer, new research shows. With alcohol use, however, the opposite is true.

The results, which were published in the October 15th issue of the American Journal of Epidemiology, also confirmed previous research showing that smoking was more strongly associated with laryngeal cancer and that alcohol consumption was more strongly associated with pharyngeal and oral cavity cancers.

“Cigarette smoking and alcohol consumption are known risk factors for head and neck cancers, including cancers of the larynx, oral cavity, and pharynx,” co-researcher Dr. Jay H. Lubin, of the National Cancer Institute, Rockville, Maryland, told Reuters Health. “This paper presented a detailed quantitative evaluation of their effects, using data which were pooled from 15 case-control studies.”

The researchers modeled the excess odds ratio (EOR) to assess risk by total exposure (pack-years and drink-years), as well as the modification of risk by exposure rate (cigarettes/day and drinks/day).

The smoking analysis included 1761 laryngeal, 2453 pharyngeal, and 1990 oral cavity cancer cases. For controls, 7963 were included for laryngeal and 10,114 for pharyngeal and for oral cavity cancer cases. The alcohol analysis included 2551 laryngeal, 3693 pharyngeal, and 3116 oral cavity cancer cases. For controls, 12,179 were included for laryngeal cancer and 15,589 for pharyngeal and oral cavity cancer cases.

While smoking increased the risk of all head and neck cancers, the association was markedly greater for larynx cancer than for pharyngeal and oral cavity cancers. The risk of cancers of the oral cavity and pharynx were similar.

In addition, the amount of additional smoking-related risk was influenced by the manner of cigarette consumption. “For example, suppose two individuals had the same total cigarette exposure (total pack-years of smoking),” Dr. Lubin explained. “Then, while both individuals will have substantially increased risk of head and neck cancer compared to someone who never smoked, the individual who smoked fewer cigarettes per day for longer duration had an even greater risk of disease than the individual who smoked more cigarettes per day for shorter duration.”

Alcohol consumption increased the odds ratios for all head and neck cancer sites relative to someone who never consumed alcohol. The risk patterns for oral cavity and pharynx cancers were again similar, with odds ratios greater for oral cavity/pharynx cancer than for larynx cancer.

“We again found that consumption patterns influenced disease risks,” Dr. Lubin said. “For two individuals with the same total alcohol consumption (drink-years), both will have an increased odds ratio for head and neck cancer, but the individual who consumed a greater number of drinks per day for a shorter duration would have an even greater risk of disease compared to the individual who consumed a smaller number of alcoholic drinks per day for a longer duration.”

Dr. Lubin noted that the patterns of odds ratios with smoking and drinking “may reflect underlying biological mechanisms. The patterns of odds ratios with smoking are consistent with several plausible biological mechanisms for the induction of cancer by various carcinogens in tobacco smoke, including increased DNA repair, saturation of activation pathways and increased induction of detoxification enzymes.”

Source:
Am J Epidemiol 2009;170:937-947.