The future of medical sciences and stomatology as its undoubted part, is more and more directed towards a general prevention of origin and development of diseases, unraveling causes of disease processes of organ systems of the human body. Despite enormous efforts and sources dedicated to basic and applied oncology research, a clinically useful method for identification of the initial transformation event (the time and place) of a normal cell into a tumor cell, has not yet been found. Malignant tumors are therefore diagnosed only on the basis of their typical or non-specific local, regional or remote symptoms. These tumors become symptomatic, although, when there are about 109 (roughly one milliard) tumor cells present. To achieve this amount (1 gram or 1 cm3), 30-fold mitotoic division of the actual number of initially transformed cells is required. The critical lethal limit of the order of magnitude 1012 tumor cells (1 billion cells, 1000 grams or 1 dm3) needs theoretically only another 10 divisions of the existing cell mass. From a simplified analysis of the tumor growth kinetics, it may be concluded that at the time of diagnosis, a tumor (109 cells) has already spent most (about three quarters) of its biological existence in an affected organ. Due to the fact that the doubling period of cellular division is about 30-60 days for human solid tumors, it is apparent that a prognosis and future of a patient depends on every month or even day during which a malignant tumor is present. The oncological prevention and timely diagnosis are thus crucial parameters of success of the oncological therapy and oncologic care in general.
From the dynamics and chronology of tumor processes point of view, the oncological prevention contains three steps.
The primary prevention has a general impact. It is based on the finding that 70 to 90% of malignant tumors are caused by exogenous factors. Only a small part is determined by genetic or unexplained etiologic factors. According to the World Health Organization, the tobacco, concentrated alcohol, high fat , high protein and high calories diet with shortage of vitamins (A, E and C), occupational conditions and environment (chemicals, dyes, asbestos), polluted environment (industrial products and exhalations, traffic), medications (cytostatic drugs, hormones) and medical techniques (diagnostic and therapeutic irradiation), solar and ultraviolet rays, and finally infections (viral, mycotic, bad hygiene) are proven carcinogenic factors. The oral, nasal and pharyngeal cavities, that form a common gateway of the airway-digestive tract, have therefore to be viewed as an area of high oncological risk due to the primary contact with external carcinogens.
Many external factors responsible for appearance of malignant tumors either cannot be influenced (climatic, geographical or geological conditions), or can be changed by an aimed policy of a government (air and water pollution, energy sources, traffic systems, health care and social security strategies). A collaboration and positive approach is also required by an individual person in creation of personal microenvironment. It concerns especially changing health risk habits, such as smoking, alcoholism, drug abuse, and a positive orientation towards the healthy diet and hygiene (oral hygiene). The health care system has to revise and reduce unreasonable use of risky diagnostic and therapeutic methods (radiodiagnostics, radiotherapy, pharmaceuticals with toxic and mutagenic effects). Providing the primary oncological prevention together with a positive individual approach towards “fighting cancer” would utilize controlled coordination of ecological, health and social policies, it is reasonable to believe that oncological mortality would show a statistically significant decrease already by the year 2000.
The secondary prevention represents an early recognition of a malignant tumor process already at the pre-clinical stage. It is the phase that precedes infiltration of a tumor into deep tissues and its propagation into adjacent structures and regional lymph nodes. In praxis, the term secondary prevention correlates to the oncological screening and also an early diagnostics. The secondary oncological prevention focuses on a particular anatomical area, a particular organ or organ system. The scope of this prevention is the search for particular, sometimes specific signs and lesions that mark a possibility of formation or presence of a malignant process. One of the lawful duties of a dentist it is to perform an oncological checking of the oral cavity and the whole orofacial area at each patient. This area also includes the oropharynx, salivary glands, upper and lower jaws including the mandibular joint, and the regional lymphatic system. A complete examination of the oral mucosa by aspection has to be completed by palpation, bimanual in the case of the mouth base and salivary glands. Attention has to be paid also to peri-oral tissues (lips, skin of the face, cheek muscles). All deviations of appearance, color and coherent mucous cover have to be recorded. The same applies to areas of palpation resistance on jaws and to suspect regions on the vermilion and skin of the face. All suspect lesions, especially chronic mucous ulcerations have to be checked again by a physician in 14 to 21 days. If the lesion does not disappear or heal clearly, one has to consider its malignant etiology and to arrange its immediate verification at a specialized department (dept. of oral and maxillo-facial surgery). Verification is usually performed by a biopsy. If positive, it requires an instantaneous oncological therapy. Incompliance with the above rules of oncological prevention is a serious violation of professional responsibility and medical ethics, and as such it may be the reason for expert evaluation of an eventual negligence of a mandatory care resulting in an injury to a patient.
Finding and treatment of mucous lesions that may be starting points of a malignant transformation belong to a dentist’s duties in the frame of the secondary prevention. Among these lesions there are chronic inflammations of the oral mucosa and the tongue (namely those of viral and mycotic origin), chronic traumatization of mucosa (untreated radices, frangible teeth crowns, wrong teeth fillings and dentures, electro-chemical irritation). Overall bad oral hygiene creates also a predisposition for malignant processes, especially if combined with alcohol and tobacco abuse. All these dental ailments have to be cured properly in order to prevent a possible malignancy.
A dentist has to be educated about the group of precancerous states (pre-neoplasias). An example of obligatory precancerous diseases (regularly leading to a malignancy) is xeroderma pigmentosum of the facial skin and keratosis of the vermilion. Among facultative precancerous conditions (potentially leading to a malignancy) there are leukoplakias of verrucous or erosive types, erythroplakias that in the form of Bowen’s disease represent already a form of intra-epithelial carcinomas (a carcinoma in situ). Glossitis rhombica mediana and the oral melanosis which may be an etiological basis of the malignant melanoma, belong to the group of facultative pre-neoplasias. Odontogenous cysts (mainly the kerato-cysts) and indeed all benign, epithelial and mesenchymal tumors have to be considered as potential pre-neoplasias. All these formations should be surgically removed in a radical and timely manner. Syndromes with an intra-oral symptomatology are also worth mentioning. Those are for instance, the Sjögren’s syndrome that has a possibility of formation of an atrophic oral mucosa carcinoma, or the Plummer-Vinson’s syndrome that indicates a possible carcinoma of the esophagus and the cardia. Under the secondary prevention, all precancerous conditions (pre-neoplasias) have to be consulted with an expert who specializes at orofacial oncology and filed at an oncological register.
The dentist’s role at the secondary oncological prevention is demanding and important. His/her diagnostic opinion and expertise is frequently crucial for therapy of an oncological disorder. On the other hand, a hesitant or alibiing behavior may bring problems not only to a patient, but to an undependable physician as well.
The tertiary prevention includes measures and procedures of the secondary prevention transferred into a post-therapeutical follow-up care. It is aimed at checking the area of the primary malignant process and the lymphatic system of this area. The prevention is carried out under the mandatory oncological follow-up. Since the majority of orofacial tumors reappear during the first two years after therapy, the following time schedule for follow-up checks is recommended: a patient is examined every month during the first six months, and in two-months intervals during the second semester. During the second year, a patient undergoes a follow-up examination at least every 3 months. If a detailed examination at the end of the second year is negative, an oncological checking is then required once every half a year. A malignant process is regarded as cured after 5 years of non-symptomatic course since a therapy had stopped. Nevertheless, follow-up examinations should continue with the frequency at least once a year, practically in a permanent manner. The reasons for that can be both late recurring tumors from hidden focuses and statistically proven increased appearance of new (secondary) tumors induced by previous intense therapy by cytostatics or radiation. These tumors may appear at locations which have no anatomical association with the primary tumor. Increased attention has to be paid to timely identification of regional and sometimes also remote metastases. These metastases can cause therapy to be unsuccessful at the end, rather than local recurrences. At this phase of care about oncological patients, special diagnostic methods such as computer tomography, nuclear magnetic resonance, sonography and measuring levels of tumor markers (carcino-embryonic antigen - CEA) are widely used.
The systematic tertiary prevention has high importance for a definite prognosis of a malignant disease. Timely identification of a recurrence or a residuum that has not been affected by a therapy enables for successful treatment and leads often to a final cure of a malignant disease.
Oncological prevention combines a diagnostic awareness of a practical stomatologist with functions of a specialist for oncological surgery in the field of therapy of orofacial tumors. Primarily such a coordinated collaboration can help to meet strategies of the WHO in increasing the anti-tumor therapy up to 65% from today’s 50% by the end of the second millennium. The stomatology field has to contribute to this goal, too.