Hormone factors play a favorable role in female head and neck cancer risk

Due to lower female incidence, estimates of exogenous and endogenous hormonal factors in head and neck cancers (HNCs, comprising cancers of the oral cavity, oropharynx, hypopharynx, and larynx) among women have been inconsistent and unable to account for key HNC risk factors. We pooled data from 11 studies from Europe, North America, and Japan. Analysis included 1572 HNC female cases and 4343 controls. Pooled odds ratios (ORs) estimates and their 95% confidence intervals (CIs) were calculated using multivariate logistic regression models adjusting for tobacco smoking and alcohol drinking. Lower risk was observed in women who used hormone replacement therapy (HRT) (OR = 0.58; 95% CI: 0.34-0.77). Pregnancy (OR = 0.61; 95% CI: 0.42-0.90) and giving birth (OR = 0.59; 95% CI: 0.38-0.90) at <35 years of age were inversely associated with HNCs. An inverse association with HNC was observed with age at start of HRT use (OR = 0.59; 95% CI: 0.39-0.90) for each additional 10 years and with duration of use (OR = 0.87; 95% CI: 0.76-0.99 for every 3 years). Exogenous female hormone use is associated with a nearly twofold risk reduction in female HNCs. The lower female HNC incidence may, in part, be explained by endogenous and exogenous estrogen exposures.