Pooled analysis of rare subgroups: a) nonsmokers & nondrinkers, b) early onset cases (Hashibe/Boffetta/Brennan, IARC)
Approximately 5% of oral cavity and pharynx cancers are diagnosed in individuals less than 40 years of age, and 17% of oral cancers are diagnosed in individuals less than 50 years of age, according to Surveillance, Epidemiology and End Results (SEER) data. An increase in incidence and mortality, especially for tongue carcinomas among young men, had been noted in the US and Europe. Some studies report similar risk factor patterns as those of older patients while other studies reported low prevalence of tobacco and alcohol habits, suggesting a stronger role for other risk factors among young patients. Several studies investigating possible risk factors such as marijuana smoking, sexual history, family history of cancer and infectious agents such as HPV, for young head and neck cancer cases have thus far been inconclusive.
Head and neck cancers among nonsmokers have been suggested as clinically distinct, with fewer p53 mutations, a lower frequency of loss of heterozygosity at chromosomes 3p, 4q, 11q13, and fewer microsatellite alterations, compared to cases who smoked. Several case-control studies with less than 100 cases have been conducted for nonsmokers and nondrinkers; studies with larger numbers of nonsmokers and nondrinkers are difficult to conduct. Subgroup analysis of nonsmokers and nondrinkers is effective in establishing the etiologic role of other risk factors since tobacco and alcohol habits are strong head and neck cancer risk factors that may act as confounders. Potential risk factors for head and neck cancers, which have been explored but require more evidence, include passive smoking, marijuana use, and low BMI.
To address some of these issues, we will conduct two sets of pooled analyses on:
- young subjects,
- nonsmokers and nondrinkers.
Our specific aims are:
- for young onset head & neck cancers, to test the hypotheses of a lesser role of tobacco and alcohol habits, and a stronger role for family history of cancer, marijuana use, smokeless tobacco, and sexual history,
- to identify the relationship of tobacco in nondrinkers, of alcohol in nonsmokers, and the etiologic roles of marijuana use, passive smoking and low body mass index independent from those of tobacco and alcohol for head & neck cancer.
This project is supported by a NIH grant from the National Cancer Institute (CA113157).