Cancers of the oral cavity (ICD C00-C14) belong to the tumors of the highest morbidity and mortality. Their epidemiological characteristics are determined by geographical factors: they are more frequent in the developed countries than in the developing ones.
Unfortunately, Hungary appears to be in a leading position regarding both the morbidity and mortality of oral cancer. This is well reflected in the age-standardized incidence rates of GLOBOCAN 2012: the ASR-W of Hungary in 2012 was 9.7 , while of the neighboring countries, Slovakia scored 6.5, Romania 5.4, and Austria only 4.2. In Europe, Greece scored the lowest (1.6). With a score of 9.7, Hungary is the first not only in Central Europe, but in the entire European region. Data of the International Association of Cancer Registries (IACR) and data from the national cancer registry of Hungary (Nemzeti Rákregiszter) show the same.
The causes of this unfortunate situation have not been clarified, and it probably cannot be explained by a few simple and well-known factors, such as smoking or excessive alcohol consumption (or the combination of these). These factors play a significant role in the pathogenesis of the oral cancers of the Hungarian population beyond doubt. However, the increasing representation of non-smoking and non-drinking elderly women and young adults among the Hungarian oral cancer patients is definitely against such a simplifying explanation.
Certainly, this sadly notable position of Hungary on the international map of oral cancer is an incentive to the Hungarian researcher of oral health to focus on the causes, consequences and potential cures for oral cancer, especially squamous cell carcinoma (OSCC). This, however, is a vast field of study. In the present thesis I narrow my focus down to two oral cancer-related questions, both rooted in the microbiology of the oral cavity. One is considered by many as a cause or promoter of OSCC, the other is obviously a consequence.
Yeasts (especially Candida spp.) have long been suspected as causative agents of oral malignant and premalignant states. The thesis discusses the yeast microflora of the oral cavity in OSCC based on our own research, considering also the specific question of the role of lipase/protease activity in epithelial colonization. It is also known that the microbial composition of the oral cavity in OSCC differs from that of the healthy oral cavity both in qualitative and quantitative respects.
This also means that the composition of the exhaled air of OSCC patients is different from that of healthy subjects, which can lead to oral malodor (halitosis). This, of course, can lead to serious psychosocial consequences, which makes halitosis in oral cancer (and otherwise) an important problem to be addressed. At the same time, the altered composition of the exhaled air could offer a new diagnostic possibility, even if this topic is scarcely researched in oral cancer.
One of the reasons for the relative lack of research in this area is that the available methodologies are not precise and reliable enough. In the present thesis I describe a methodological improvement developed by our team and tested with OSCC patients.