Prognostic markers found for oropharyngeal cancer
medwireNews: Alcohol consumption and p16 expression are associated with prognosis in patients with oropharyngeal squamous cell carcinoma (OPSCC), Japanese researchers believe.
Writing in Cancer, Yuki Saito (University of Tokyo) and colleagues also note that the incidence of OPSCC due to infection with human papillomavirus (HPV) is increasing in the Japanese population.
The reasons for the increase "are unclear but may be related to the westernization of sexual habits," they hypothesize.
Saito's team used immunohistochemistry to analyze tumor samples from 173 patients with OPSCC who were treated at a single center between 2000 and 2011. All but 17 of the patients were men, the median age was 64 years, and the most common tumor sites were the tonsil and base of tongue.
Immunostaining revealed that tumors from women were more likely to express p16 - a cyclin-dependent kinase inhibitor and tumor suppressor - than were tumors from men, at 47.1% versus 27.6%.
Expression of p16 was also significantly more likely in nonsmokers than smokers (31.4 vs 28.7%) and in nondrinkers than drinkers (58.2 vs 22.3%). Expression differed by tumor site, with the prevalence of p16-positive OPSCC being 33.7% in tonsillar carcinoma, 28.6% in tongue base carcinoma, 0% in posterior wall carcinoma, and 18.8% in soft palate carcinoma.
In a time-dependent analysis, the prevalence of p16-positive OPSCC tumors more than doubled over the study period, from 15.2% in 2000-2003 to 33.3% in 2008-2011. Also over this time, the prevalence of p16-positive tumors rose among nonsmokers (from 21.2 to 27.8%) and among nondrinkers (from 6.1 to 25.0%).
Finally, in multivariate analysis, positive p16 expression and lack of alcohol consumption emerged as significant independent predictors for overall survival, with hazard ratios of 0.34 and 2.88, respectively.
These two factors were used to classify patients into risk for dying, such that patients who had p16-positive tumors and nondrinkers who had p16-negative tumors were at low risk (40% over 3 years) whereas drinkers who had p16-negative tumors were at high risk (60% over 3 years).
"Our report indicates that alcohol consumption, rather than tobacco smoking, was an independent factor for survival, especially among patients with p16-negative OPSCC," remark Saito et al.
"This may be another racial difference between the Japanese and US and Western European populations… This uniquely Asian genetic alteration may render p16-negative OPSCC less responsive to therapy; however, future studies will be needed for further elucidation."
By Joanna Lyford, Senior medwireNews Reporter