出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2012/09/06 19:12:16」(JST)
| Head and neck cancer | |
|---|---|
| Classification and external resources | |
| ICD-10 | C07-C14 C32-C33 |
| ICD-9 | 140-149 |
| MeSH | D006258 |
Head and neck cancer refers to a group of biologically similar cancers that start in the lip, oral cavity (mouth), nasal cavity (inside the nose), paranasal sinuses, pharynx, and larynx. 90% of head and neck cancers are squamous cell carcinomas (SCCHN),[1] originating from the mucosal lining (epithelium) of these regions.[2] Head and neck cancers often spread to the lymph nodes of the neck, and this is often the first (and sometimes only) sign of the disease at the time of diagnosis. Head and neck cancer is strongly associated with certain environmental and lifestyle risk factors, including tobacco smoking, alcohol consumption, UV light, particular chemicals used in certain workplaces, and certain strains of viruses, such as human papillomavirus.[3] These cancers are frequently aggressive in their biologic behavior; patients with these types of cancer are at a higher risk of developing another cancer in the head and neck area.[3] Head and neck cancer is highly curable if detected early, usually with some form of surgery although chemotherapy and radiation therapy may also play an important role. The 2009 estimated number of head and neck cancer in the US is of 35,720 new cases.[4]
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Head and neck squamous cell carcinomas (HNSCC's) make up the vast majority of head and neck cancers, and arise from mucosal surfaces throughout this anatomic region. These include tumors of the nasal cavities, paranasal sinuses, oral cavity, nasopharynx, oropharynx, hypopharynx, and larynx.
Squamous cell cancers are common in the oral cavity, including the inner lip, tongue, floor of mouth, gingivae, and hard palate. Cancers of the oral cavity are strongly associated with tobacco use, especially use of chewing tobacco or "dip", as well as heavy alcohol use. Cancers of this region, particularly the tongue, are more frequently treated with surgery than are other head and neck cancers.
Surgeries for oral cancers include
The defect is typically covered/improved by using another part of the body and/or skin grafts and/or wearing a prosthesis.
Nasopharyngeal cancer arises in the nasopharynx, the region in which the nasal cavities and the Eustachian tubes connect with the upper part of the throat. While some nasopharyngeal cancers are biologically similar to the common HNSCC, "poorly differentiated" nasopharyngeal carcinoma is distinct in its epidemiology, biology, clinical behavior, and treatment, and is treated as a separate disease by many experts.
Oropharyngeal squamous cell carcinomas (OSCC) begins in the oropharynx, the middle part of the throat that includes the soft palate, the base of the tongue, and the tonsils. Squamous cell cancers of the tonsils are more strongly associated with human papillomavirus infection than are cancers of other regions of the head and neck.
The hypopharynx includes the pyriform sinuses, the posterior pharyngeal wall, and the postcricoid area. Tumors of the hypopharynx frequently have an advanced stage at diagnosis, and have the most adverse prognoses of pharyngeal tumors. They tend to metastasize early due to the extensive lymphatic network around the larynx.
Laryngeal cancer begins in the larynx or "voice box." Cancer may occur on the vocal folds themselves ("glottic" cancer), or on tissues above and below the true cords ("supraglottic" and "subglottic" cancers respectively). Laryngeal cancer is strongly associated with tobacco smoking.
Surgery can include partial laryngectomy (removal of part of the larynx) and total laryngectomy (removal of the whole larynx). If the whole larynx has been removed the person is left with a permanent tracheostomy and can learn to speak again in a new way with the help of intensive teaching and speech therapy and/or an electronic device.
Cancer of the trachea is a rare malignancy which can be biologically similar in many ways to head and neck cancer, and is sometimes classified as such.
Most tumors of the salivary glands differ from the common carcinomas of the head and neck in etiology, histopathology, clinical presentation, and therapy, Other uncommon tumors arising in the head and neck include teratomas, adenocarcinomas, adenoid cystic carcinomas, and mucoepidermoid carcinomas.[3] Rarer still are melanomas and lymphomas of the upper aerodigestive tract.
Throat cancer usually begins with symptoms that seem harmless enough, like an enlarged lymph node on the outside of the neck, a sore throat or a hoarse sounding voice. However, in the case of throat cancer, these conditions may persist and become chronic. There may be a lump or a sore in the throat or neck that does not heal or go away. There may be difficult or painful swallowing. Speaking may become difficult. There may be a persistent earache. Other possible but less common symptoms include some numbness or paralysis of the face muscles.
Presenting symptoms include
Alcohol and tobacco use are the most common risk factors for head and neck cancer in the United States. Alcohol and tobacco are likely synergistic in causing cancer of the head and neck.[5] Smokeless tobacco is an etiologic agent for oral and pharyngeal cancers (oropharyngeal cancer).[6] Cigar smoking is an important risk factor for oral cancers as well.[7] Other potential environmental carcinogens include occupational exposures such as nickel refining, exposure to textile fibers, and woodworking. In one large, controlled study, marijuana use was not shown to be associated with oral squamous cell carcinoma.[8] In another study, marijuana use was shown to be a potential protective factor against the development of head and neck squamous cell carcinoma.[9] However, cigarette smokers have a lifetime increased risk for head and neck cancers that is 5- to 25-fold increased over the general population.[10] The ex-smoker's risk for squamous cell cancer of the head and neck begins to approach the risk in the general population twenty years after smoking cessation. The high prevalence of tobacco and alcohol use worldwide and the high association of these cancers with these substances makes them ideal targets for enhanced cancer prevention.
Dietary factors may contribute. Excessive consumption of processed meats and red meat were associated with increased rates of cancer of the head and neck in one study, while consumption of raw and cooked vegetables seemed to be protective.[11]
Vitamin E was not found to prevent the development of leukoplakia, the white plaques that are the precursor for carcinomas of the mucosal surfaces, in adult smokers.[12] Another study examined a combination of Vitamin E and beta carotene in smokers with early-stage cancer of the oropharynx, and found a worse prognosis in the vitamin users.[13]
Betel nut chewing is associated with an increased risk of squamous cell cancer of the head and neck.[14]
Recent evidence is accumulating pointing to a viral origin for some head and neck cancers.[15]
Human papillomavirus (HPV), in particular HPV16, is a causal factor for some head and neck squamous cell carcinoma (HNSCC).[16][17] Approximately 15 to 25% of HNSCC contain genomic DNA from HPV,[18] and the association varies based on the site of the tumor, especially HPV-positive oropharyngeal cancer, with highest distribution in the tonsils, where HPV DNA is found in (45 to 67%) of the cases,[19] less often in the hypopharynx (13%–25%), and least often in the oral cavity (12%–18%) and larynx (3%–7%).[20]
Some experts estimate that while up to 50% of cancers of the tonsil may be infected with HPV, only 50% of these are likely to be caused by HPV (as opposed to the usual tobacco and alcohol causes). The role of HPV in the remaining 25-30% is not yet clear.[21]
Epstein-Barr virus (EBV) infection is associated with nasopharyngeal cancer.[15] Nasopharyngeal cancer occurs endemically in some countries of the Mediterranean and Asia, where EBV antibody titers can be measured to screen high-risk populations.[15] Nasopharyngeal cancer has also been associated with consumption of salted fish, which may contain high levels of nitrites.
The presence of acid reflux disease (GERD - gastroesphogeal reflux disease) or larynx reflux disease can also be a major factor. In the case of acid reflux disease, stomach acids flow up into the esophagus and damage its lining, making it more susceptible to throat cancer.
Patients after hematopoietic stem cell transplantation (HSCT) are at a higher risk for oral squamous cell carcinoma. Post-HSCT oral cancer may have more aggressive behavior with poorer prognosis, when compared to oral cancer in non-HSCT patients.[22] This effect is supposed to be owing to the continuous lifelong immune suppression and chronic oral graft-versus-host disease.[22]
There are a wide variety of factors which can put someone at a heightened risk for throat cancer. Such factors include smoking or chewing tobacco or other things, such as gutkha, or paan, heavy alcohol consumption, poor diet resulting in vitamin deficiencies (worse if this is caused by heavy alcohol intake), weakened immune system, asbestos exposure, prolonged exposure to wood dust or paint fumes, exposure to petroleum industry chemicals, and being over the age of 55 years. Another risk factor includes the appearance of white patches or spots in the mouth, known as leukoplakia;[3] in about ⅓ of the cases this develops into cancer.
A patient usually presents to the physician complaining of one or more of the above symptoms. The patient will typically undergo a needle biopsy of this lesion, and a histopathologic information is available, a multidisciplinary discussion of the optimal treatment strategy will be undertaken between the radiation oncologist, surgical oncologist, and medical oncologist.
Throat cancers are classified according to their histology or cell structure, and are commonly referred to by their location in the oral cavity and neck. This is because where the cancer appears in the throat affects the prognosis - some throat cancers are more aggressive than others depending upon their location. The stage at which the cancer is diagnosed is also a critical factor in the prognosis of throat cancer.
Squamous cells are the epithelium (tissue layer) that is the surface cells of much of the body. Skin and mucous membranes are squamous cells. This is the most common form of larynx cancer, accounting for over 90% of throat cancer.[3] Squamous cell carcinoma is most likely to appear in males over 40 years of age with a history of heavy alcohol use coupled with smoking.
Adenocarcinoma is a cancer of the columnar epithelium typical of the lower esophagus. It is typical of Barrett's esophagus but may be at another location. Adenocarcinoma is thought of as a product of Barrett's esophagus.
Avoidance of recognised risk factors (as described above) is the single most effective form of prevention. Regular dental examinations may identify pre-cancerous lesions in the oral cavity.
When diagnosed early, oral, head and neck cancers can be treated more easily and the chances of survival increase tremendously.
It is expected that HPV vaccines may reduce the risk of HPV induced head and neck cancer.[23]
A study, published in the Cancer Prevention Research journal, showed that long-term cannabis users were, roughly, 62 percent less likely to develop head and neck cancers than people who never used cannabis.[24]
Improvements in diagnosis and local management, as well as targeted therapy, have led to improvements in quality of life and survival for head and neck cancer patients since 1992.[25]
After a histologic diagnosis has been established and tumor extent determined, the selection of appropriate treatment for a specific cancer depends on a complex array of variables, including tumor site, relative morbidity of various treatment options, patient performance and nutritional status, concomitant health problems, social and logistic factors, previous primary tumors, and patient preference. Treatment planning generally requires a multidisciplinary approach involving specialist surgeons and medical and radiation oncologists.
Several generalizations are useful in therapeutic decision making, but variations on these themes are numerous. Surgical resection and radiation therapy are the mainstays of treatment for most head and neck cancers and remain the standard of care in most cases. For small primary cancers without regional metastases (stage I or II), wide surgical excision alone or curative radiation therapy alone is used. More extensive primary tumors, or those with regional metastases (stage III or IV), planned combinations of pre- or postoperative radiation and complete surgical excision are generally used. More recently, as historical survival and control rates are recognized as less than satisfactory, there has been an emphasis on the use of various induction or concomitant chemotherapy regimens.
Patients with head and neck cancer can be categorized into three clinical groups: those with localized disease, those with locally or regionally advanced disease, and those with recurrent and/or metastatic disease. Comorbidities (medical problems in addition to the diagnosed cancer) associated with tobacco and alcohol abuse can affect treatment outcome and the tolerability of aggressive treatment in a given patient.
Many different treatments and therapies are used in the treatment of throat cancer. The type of treatment and therapies used are largely determined by the location of the cancer in the throat area and also the extent to which the cancer has spread at time of diagnosis. Patients’ also have the right to decide whether or not they wish to consent to a particular treatment. For example, some may decide to not undergo radiation therapy which has serious side effects if it means they will be extending their lives by only a few months or so. Others may feel that the extra time is worth it and wish to pursue the treatments.
Surgery as a treatment is frequently used in most types of head and neck cancer. Usually the goal is to remove the cancerous cells entirely. This can be particularly tricky if the cancer is near the larynx and can result in the patient being unable to speak. Surgery is also commonly used to resect (remove) some or all of the cervical lymph nodes to prevent further spread of the disease.
CO2 laser surgery is also another form of treatment. Transoral laser microsurgery allows surgeons to remove tumors from the voice box with no external incisions. It also allows access to tumors that are not reachable with robotic surgery. A microscope helps the surgeon clearly view the margins of the tumor, minimizing the amount of normal tissue removed or damaged during surgery. This technique helps give the patient as much speech and swallowing function as possible after surgery.[26]
Radiation therapy is the most common form of treatment. There are different forms of radiation therapy, including 3D conformal radiation therapy, intensity-modulated radiation therapy, and brachytherapy, which are commonly used in the treatments of cancers of the head and neck. Most patients with head and neck cancer who are treated in the United States and Europe are treated with intensity-modulated radiation therapy using high energy photons.
Chemotherapy in throat cancer is not generally used to cure the cancer as such. Instead, it is used to provide an inhospitable environment for metastases so that they will not establish in other parts of the body. Typical chemotherapy agents are a combination of paclitaxel and carboplatin. Cetuximab is also used in the treatment of throat cancer.
Docetaxel-based chemotherapy has shown a very good response in locally advanced head and neck cancer. Taxotere is the only taxane approved by US FDA for Head and neck cancer, in combination with cisplatin and fluorouracil for the induction treatment of patients with inoperable, locally advanced squamous cell carcinoma of the head and neck.[27]
While not specifically a chemotherapy, amifostine is often administered intravenously by a chemotherapy clinic prior to a patient's IMRT radiotherapy sessions. Amifostine protects the patient's gums and salivary glands from the effects of radiation.[citation needed]
Photodynamic therapy may have promise in treating mucosal dysplasia and small head and neck tumors.[3] Amphinex is giving good results in early clinical trials for treatment of advanced head and neck cancer.[28]
Targeted therapy, according to the National Cancer Institute, is "a type of treatment that uses drugs or other substances, such as monoclonal antibodies, to identify and attack specific cancer cells without harming normal cells." Some targeted therapy used in squamous cell cancers of the head and neck include cetuximab, bevacizumab and erlotinib.
The best quality data are available for cetuximab since the 2006 publication of a randomized clinical trial comparing radiation treatment plus cetuximab versus radiation treatment alone.[29] This study found that concurrent cetuximab and radiotherapy improves survival and locoregional disease control compared to radiotherapy alone, without a substantial increase in side effects, as would be expected with the concurrent chemoradiotherapy, which is the current gold standard treatment for advanced head and neck cancer. Whilst this study is of pivotal significance, interpretation is difficult since cetuximab-radiotherapy was not directly compared to chemoradiotherapy. The results of ongoing studies to clarify the role of cetuximab in this disease are awaited with interest.
Another study evaluated the impact of adding cetuximab to conventional chemotherapy (cisplatin) versus cisplatin alone. This study found no improvement in survival or disease-free survival with the addition of cetuximab to the conventional chemotherapy.[30]
However, another study which completed in March 2007 found that there was an improvement in survival.[citation needed]
A 2010 review concluded that the combination of cetuximab and platin/5-fluorouracil should be considered the current standard first-line regimen.[31]
Head and neck cancer clinical trials employing bevacizumab, an inhibitor of the angiogenesis receptor VEGF, were recruiting patients As of March 2007[update].
Erlotinib is an oral EGFR inhibitor, and was found in one Phase II clinical trial to retard disease progression.[32] Scientific evidence for the effectiveness of erlotinib is otherwise lacking to this point. A clinical trial evaluating the use of erlotinib in metastatic head and neck cancer is recruiting patients as of March, 2007.
Although early-stage head and neck cancers (especially laryngeal and oral cavity) have high cure rates, up to 50% of head and neck cancer patients present with advanced disease.[33] Cure rates decrease in locally advanced cases, whose probability of cure is inversely related to tumor size and even more so to the extent of regional node involvement. Consensus panels in America (AJCC) and Europe (UICC) have established staging systems for head and neck squamous cancers. These staging systems attempt to standardize clinical trial criteria for research studies, and attempt to define prognostic categories of disease. Squamous cell cancers of the head and neck are staged according to the TNM classification system, where T is the size and configuration of the tumor, N is the presence or absence of lymph node metastases, and M is the presence or absence of distant metastases. The T, N, and M characteristics are combined to produce a “stage” of the cancer, from I to IVB.[34]
Even after successful definitive therapy, head and neck cancer patients face tremendous impacts on quality of life.[35] Despite marked advances in reconstructive surgery and rehabilitation, intensity-modulated radiotherapy (IMRT) and conservation approaches to certain malignancies, some patients continue to have significant functional deficits.[36]
Survival advantages provided by new treatment modalities have been undermined by the significant percentage of patients cured of head and neck squamous cell carcinoma (HNSCC) who subsequently develop second primary tumors. The incidence of second primary tumors ranges in studies from 9.1%[37] to 23%[38] at 20 years. Second primary tumors are the major threat to long-term survival after successful therapy of early-stage HNSCC. Their high incidence results from the same carcinogenic exposure responsible for the initial primary process, called field cancerization.
As it can impair a person’s ability to swallow and eat, throat cancer affects the digestive system. The difficulty in swallowing can lead to a person to choke on their food in the early stages of digestion and interfere with the food’s smooth travels down into the esophagus and beyond.
The treatments for throat cancer can also be harmful to the digestive system as well as other body systems. Radiation therapy can lead to nausea and vomiting, which can deprive a body of vital fluids (although these may be obtained through intravenous fluids if necessary). Frequent vomiting can lead to an electrolyte imbalance which has serious consequences for the proper functioning of the heart. Frequent vomiting can also upset the balance of stomach acids which has a negative impact on the digestive system, especially the lining of the stomach and esophagus.
In the cases of some throat cancers, the air passages in the mouth and behind the nose may become blocked from lumps or the swelling from the open sores. If the throat cancer is near the bottom of the throat it has a high likelihood of spreading to the lungs and interfering with the person’s ability to breathe; this is even more likely if the patient is a smoker, because they are highly susceptible to lung cancer.
Like any cancer, metastasization affects many areas of the body, as the cancer spreads from cell to cell and organ to organ. For example, if it spreads to the bone marrow, it will prevent the body from producing enough red blood cells and affects the proper functioning of the white blood cells and the body's immune system; spreading to the circulatory system will prevent oxygen from being transported to all the cells of the body; and throat cancer can throw the nervous system into chaos, making it unable to properly regulate and control the body.
Patients with head and neck cancer may experience the following symptoms and treatment side effects:[3]
Age-standardized death from oro-pharyngeal per 100,000 inhabitants in 2004.[39]
The number of new cases of head and neck cancers in the United States was 40,490 in 2006, accounting for about 3% of adult malignancies. 11,170 patients died of their disease in 2006.[40] The worldwide incidence exceeds half a million cases annually. In North America and Europe, the tumors usually arise from the oral cavity, oropharynx, or larynx, whereas nasopharyngeal cancer is more common in the Mediterranean countries and in the Far East. In Southeast China and Taiwan, head and neck cancer, specifically nasopharyngeal cancer is the most common cause of death in young men.[41]
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| リンク元 | 「咽頭癌」「pharyngeal neoplasm」「咽頭がん」「cancer of the pharynx」 |
| 関連記事 | 「pharyngeal」「cancer」 |