Oral and Oropharyngeal Cancer - Aspects on Epidemiology and Prognostic Markers
Abstract: Head and neck cancer is a heterogeneous group of tumours, although histopathologically, >95% are squamous cell carcinomas (SCC). Some tumours respond better to therapy than others. Not enough is known to predict the outcome and tailor individualised treatment. Although one of the main risk factors, smoking, has decreased over the last decades, some head and neck cancer groups show increasing incidence. Oral and oropharyngeal SCC (OOPHSCC) are amongst them. High risk human papillomavirus (HPV) has been reported to be found in a high proportion of OOPHSCC, especially in oropharyngeal cancers. It is presumed to be the reason for the incidence increase of oropharyngeal SCC, but not for oral SCC. Many studies, but not all, show better survival for patients with HPV positive tumours. Different methods for HPV detection are being used, making it difficult to compare results. Alpha B-crystallin, a small heat-shock protein, has in a previous study been found to be an independent prognostic marker for poor outcome in head and neck SCC. This thesis aimed to investigate the epidemiological changes for tongue cancer in the Nordic countries and to compare some possible predictive factors for OOPHSCC. During the period 1960-1994, an incidence increase in SCC of the mobile tongue in all ages, except for women aged 65-79, was observed. Data including site and histology was obtained from the national cancer registries. The increase was most pronounced in young adults (20-39 years), with a five-fold increase in men and a six-fold increase in women. Young adults had a significantly better crude, as well as relative, survival compared to older patients. In a follow-up study, the incidence trends were studied, extending the study period by 14 years, extracting data from the NORDCAN registry. The incidence increase continued for all ages, except for in young adult men. In a consecutive series of 128 OOPHSCC, no difference in five year survival was found between patients with HPV positive and HPV negative tumours. Sample collection method was by cotton tipped swab and mouth wash (SMC). When 91 patients from the same study population were analysed, instead using formalin fixed paraffin embedded tissue from their diagnostic biopsies (FFPE), again no survival difference was found. The rate of inconsistent results between SMC and FFPE was 27%. In a set of 55 OOPHSCC, alpha B-crystallin was found to be a strong independent prognostic marker for poor prognosis in oral SCC, but not in oropharyngeal SCC. The findings highlight the fact that more and more differences between oral and oropharyngeal SCC are being revealed.
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