Рак полости рта: причины, симптомы и тенденции заболеваемости.

Cancer of the lining of the lips, mouth, or upper throat
Risk factors include tobacco and alcohol use. Those who use both alcohol and tobacco have a 15 times greater risk of oral cancer than those who use neither. Other risk factors include HPV infection, chewing paan, and sun exposure on the lower lip. Oral cancer is a subgroup of head and neck cancers. Between 1999 and 2015 in the United States, the rate of oral cancer increased 6% (from 10.9 to 11.6 per 100,000). Deaths from oral cancer during this time decreased 7% (from 2.7 to 2.5 per 100,000). Oral cancer has an overall 5 year survival rate of 65% in the United States as of 2015. This varies from 84% if diagnosed when localized, compared to 66% if it has spread to the lymph nodes in the neck, and 39% if it has spread to distant parts of the body.

The signs and symptoms of oral cancer depend on the location of the tumor but are generally thin, irregular, white patches in the mouth. They can also be a mix of red and white patches (mixed red and white patches are much more likely to be cancerous when biopsied). The classic warning sign is a persistent rough patch with ulceration, and a raised border that is minimally painful. On the lip, the ulcer is more commonly crusting and dry, and in the pharynx it is more commonly a mass. It can also be associated with a white patch, loose teeth, bleeding gums, persistent ear ache, a feeling of numbness in the lip and chin, or swelling. When the cancer extends to the throat, there can also be difficulty swallowing (usually a base of tongue HPV16+ cancer) or a visibly enlarged tonsil unilaterally, also from the same etiology, painful swallowing, and an altered voice. Typically, the lesions have very little pain until they become larger and then are associated with a burning sensation. As the lesion spreads to the lymph nodes of the neck, a painless, hard mass will develop. If it spreads elsewhere in the body, general aches can develop, most often due to bone metastasis. Tobacco is estimated to increase the risk of oral cancer by 3.4 and is responsible for approximately 40% of all oral cancers.

Epidemiological evidence indicates that alcohol consumption is strongly associated with oral cancer, accounting for 20.2% of global oral cancer cases in 2020. The relative risk for oral cavity and pharynx cancer is 1.13 for light, 1.83 for moderate, and 5.13 for heavy drinking. There is a greater than multiplicative joint effect between alcohol and tobacco. The full causal relation between alcohol consumption and the elevated risk of cancer remains unclear, but acetaldehyde plays a major role. Immediately after alcohol consumption, there are elevated levels of acetaldehyde in saliva, peaking after about 2 minutes. Acetaldehyde is produced by the oral microbiome, and also by enzymes in the oral mucosa, saliva glands, and liver. It is also naturally present in alcoholic beverages. Of these, the microbiome is the major contributor, accounting for at least half of the acetaldehyde present. Poor oral hygiene, smoking, and heavy drinking induce an increase in acetaldehyde producing bacteria in the mouth. Many species of bacteria contribute to acetaldehyde production and their epidemiological significance is not known. The acetaldehyde reacts with oral epithelial cells, inducing DNA modifications, which can lead to mutations and cancer development. The ability to metabolize acetaldehyde in the mouth is limited, so it may remain in the saliva for hours. L cysteine tablets may be used to decrease acetaldehyde exposure in the oral cavity. It has been controversial if the use of alcohol based mouthwashes increases oral cancer risk. However, mouthwashes are designed for bacterial elimination, and therefore kill the microbes that metabolize ethanol to acetaldehyde, potentially reducing overall exposure to acetaldehyde and providing a protective effect. A 2020 systematic review suggested that the effect may be limited to aggravating the risks in certain populations, such as smokers, heavy drinkers, and those with poor oral health. These populations were all found to have significantly increased risks from using alcohol based mouthwash. One large pooled analysis found a 36% increase in incidence of oral cancer among never smokers never drinkers who used mouthwashes for more than 35 years. The study did not determine use of alcohol based mouthwashes but merely the use of mouthwash, although data for a subset of participants suggested most mouthwashes used were alcohol based.

Infection with human papillomavirus (HPV), particularly type 16 (there are over 180 types), is a known risk factor and independent causative factor for oral cancer. A fast growing segment of those diagnosed does not present with the historic stereotypical demographics. Historically that has been people over 50, blacks over whites 2 to 1, males over females 3 to 1, and 75% of the time people who have used tobacco products or are heavy users of alcohol. This new and rapidly growing subpopulation between 30 and 50 years old, is predominantly nonsmoking, white, and males slightly outnumber females. Recent research from multiple peer reviewed journal articles indicates that HPV16 is the primary risk factor in this new population of people with oral cancer. HPV16 (along with HPV18) is the same virus responsible for the vast majority of all cervical cancers and is the most common sexually transmitted infection in the US. Oral cancer in this group tends to favor the tonsil and tonsillar pillars, base of the tongue, and the oropharynx. Recent data suggest that individuals who develop the disease from this particular cause have a significant survival advantage, as the disease responds better to radiation treatments than tobacco caused disease.

Chewing betel, paan and Areca is known to be a strong risk factor for developing oral cancer even in the absence of tobacco. It increases the rate of oral cancer 2.1 times, through a variety of genetic and related effects through local irritation of the mucous membrane cells, particularly from the areca nut and slaked lime. This effect is supposed to be owing to the continuous lifelong immune suppression and chronic oral graft versus host disease. In the Indian subcontinent oral submucous fibrosis is very common due to betel nut chewing. This condition is characterized by limited opening of mouth and burning sensation on eating of spicy food. This is a progressive lesion in which the opening of the mouth becomes progressively limited, and later on even normal eating becomes difficult.

Chemotherapy and radiotherapy are most often used, as an adjunct to surgery, to control oral cancer that is greater than stage 1, or has spread to either regional lymph nodes or other parts of the body. Monoclonal antibody therapy (with agents such as cetuximab) have been shown to be effective in the treatment of squamous cell head and neck cancers, and are likely to have an increasing role in the future management of this condition when used in conjunction with other established treatment modalities, although it is not a replacement for chemotherapy in head and neck cancers.

Following treatment, rehabilitation may be necessary to improve movement, chewing, swallowing, and speech. Speech and language pathologists may be involved at this stage. Treatment of oral cancer will usually be by a multidisciplinary team, with treatment professionals from the realms of radiation, surgery, chemotherapy, nutrition, dentistry, and even psychology all possibly involved with diagnosis, treatment, rehabilitation, and care. Due to the location of oral cancer, there may be a period where the person requires a tracheotomy and feeding tube.

Survival rates for oral cancer depend on the precise site and the stage of the cancer at diagnosis. Overall, 2011 data from the SEER database shows that survival is around 57% at five years when all stages of initial diagnosis, all genders, all ethnicities, all age groups, and all treatment modalities are considered. Survival rates for stage 1 cancers are approximately 90%, hence the emphasis on early detection to increase survival outcome for people. Similar survival rates are reported from other countries, such as Germany.

Globally, it newly occurred in about 355,000 people and resulted in 177,000 deaths in 2018. Oral cancer occurs more often in people from lower and middle income countries.

Europe places second highest after Southeast Asia among all continents for age standardised rate (ASR) specific to oral and oropharyngeal cancer. It is estimated that there were 61,400 cases of oral and lip cancer within Europe in 2012. Hungary recorded the highest number of mortality and morbidity due to oral and pharyngeal cancer among all European countries while Cyprus reported the lowest numbers

British Cancer Research found 2,386 deaths due to oral cancer in 2014; while most oral cancer cases are diagnosed in older adults between 50 and 74 years old, this condition can affect the young as well; 6% of people affected by oral cancer are under 45 years of age. The United Kingdom is 16th lowest for males and 11th highest for females for oral cancer incidence among Europe. Additionally, there is a regional variability within the United Kingdom, with Scotland and northern England having higher rates than southern England. The same analysis applies to lifetime risk of developing oral cancer, as in Scotland it is 1.84% in males and 0.74% in females, higher than the rest of the UK, being 1.06% and 0.48%, respectively. Oral cancer is the sixteenth most common cancer in the United Kingdom (around 6,800 people were diagnosed with oral cancer in the United Kingdom in 2011), and it is the 19th most common cause of cancer death (around 2,100 people died from the disease in 2012). The high incidence rate of oral and pharyngeal cancer in Denmark could be attributed to their higher alcohol intake than citizens of other Scandinavian countries and low intake of fruits and vegetables in general.

Hungary (23.3), Slovakia (16.4), and Romania (15.5) reported the highest incidences of oral and pharyngeal cancer. Cigarette smoking, excessive alcohol consumption, inequalities in the care received by people with cancer, and gender specific systemic risk factors have been determined as the leading causes for the high morbidity and mortality rates in Hungary.

The incidence rates of oral cancer in western Europe found France, Germany and Belgium to be highest. The ASRs (per 100,000) were 15.0, 14.6, and 14.1, respectively. When filtered by gender category, the same countries rank top 3 for male, however, in different order of Belgium (21.9), Germany (23.1), and France (23.1). France, Belgium, and the Netherlands rank highest for females, with ASRs 7.6, 7.0, and 7.0, respectively. Of all the cancers, oral cancer attributes to 3% in males, opposed to 2% in women. New cases of oral cancer in US as of 2013, approximated almost 66,000 with almost 14000 attributed from tongue cancer, and nearly 12000 from the mouth, and the remainder from the oral cavity and pharynx. In the previous year, 1.6% of lip and oral cavity cancers were diagnosed, where the age standardised incidence rate (ASIR) across all geographic regions of United States of America estimates at 5.2 per 100,000 population. It is the eleventh most common cancer in the United States among males while in Canada and Mexico it is the twelfth and thirteenth most common cancer respectively. The ASIR for lip and oral cavity cancer among men in Canada and Mexico is 4.2 and 3.1, respectively. In Brazil, however, lip and oral cavity cancer is the 7th most common cancer, with an estimated 6,930 new cases diagnosed in the year 2012. This number is rising and has an overall higher ASIR at 7.2 per 100,000 population whereby an approx 3000 deaths have occurred In South East Asia and Arab countries, although the prevalence is not as high, estimated incidences of oral cancer ranged from 1.6 to 8.6/ 100,000 and 1.8 to 2.13/ 100,000 respectively. According to GLOBOCAN 2012, the estimated age standardised rates of cancer incidence and mortality was higher in males than females. However, in some areas, specifically South East Asia, similar rates were recorded for both genders.

Oral cancer is the third most common form of cancer in India with over 77 000 new cases diagnosed in 2012 (2.3:1 male to female ratio). Studies estimate over five deaths per hour. One of the reasons behind such high incidence might be popularity of betel and areca nuts, which are considered to be risk factors for development of oral cavity cancers.

There is limited data for the prevalence of oral cancer in Africa. The following rates describe the number of new cases (for incidence rates) or deaths (for mortality rates) per 100 000 individuals per year. The mortality rate is significantly lower than the incidence rate at 1.0 for both sexes. The rate is higher in males at 1.4 and lower in females at 0.6. Table 1 provides age standardised incidence and mortality rates for oral cancer based on the location in the mouth. The location 'other mouth' refers to the buccal mucosa, the vestibule and other unspecified parts of the mouth. The data suggests lip cancer has the highest incidence rate while gingival cancer has the lowest rate overall. In terms of mortality rates, oropharyngeal cancer has the highest rate in males and tongue cancer has the highest rate in females. Lip, palatal and gingival cancer have the lowest mortality rates overall. Dogs that are a breed that is at higher risk of developing oral cancer are more susceptible. Tumors that are found early in development can be removed by surgery, however some cases involve removing a part of the jaw. Chemotherapy is used following surgeries or to remove a tumor that cannot be accessed. Tumors that are caught when the cancer has already spread to other places of the body will result in the dog living for only 6 12 more months. The most common type of oral cancer seen in cats is squamous cell carcinoma. Due to tumors developing in hidden spots such as beneath the tongue, when the tumors in the cats mouth are caught it is often untreatable. Risk factors include secondhand smoke, as the smoke settles on the fur which is ingested when cats groom, and potentially the over consumption of canned food and use of flea collars.