Radiation therapy for laryngeal cancer Laryngeal cancer ranks second in the incidence rate of malignant tumors of head and neck, and it is a kind of tumor with better efficacy of radiation therapy, especially for early stage of vocal folds cancer. If correct radiotherapy plan and fine irradiation technique are adopted, the efficacy of radiation therapy is no less than that of surgical treatment, and the patients can save the function of phonation, which can better guarantee the quality of life, and it is one of the most common types of disease in Radiotherapy Department. Epidemiology and etiology In recent years, the incidence of laryngeal cancer has a tendency of gradual growth, and its incidence rate has regional differences. The incidence rate of laryngeal cancer is significantly higher in males than females, with the ratio of male to female being 4-6:1, and the age of onset of the disease is usually between 50 and 70 years old. The cause of laryngeal cancer is still unknown. It is generally believed that laryngeal cancer is related to smoking, and asbestos dust also has a certain relationship; some people think that the occurrence of laryngeal cancer may be related to human papillomavirus infection; other studies have shown that laryngeal cancer has a certain relationship with oncogenes such as H-ras and C-myc, oncogenes such as P53 and Rb, and androgens. The larynx is located in the middle of the front of the neck, equivalent to the level of the 4th to 6th cervical vertebrae. It is connected with laryngopharynx and oropharynx in the upper part and trachea in the lower part. The larynx consists of epiglottis cartilage, thyroid cartilage, cricoid cartilage constituting the scaffolding, and there are three pairs of small cartilage philtrum cartilage, small angle cartilage and cuneiform cartilage attached to the scaffolding. The laryngeal cavity is covered with mucous membrane, and there are two pairs of longitudinal mucous membrane walls called ventricular zone and vocal zone on both sides of the laryngeal cavity, which divides the laryngeal cavity into supraglottic, glottic, and infraglottic zones. (According to UICC 1997 staging criteria) Lymphatic drainage of the larynx: two groups: supraglottic and subglottic. The supraglottic group includes the lymphatic vessels of the epiglottic cartilage, philtrum cartilage, ventricular band, laryngeal ventricle, and vocal cords, etc. The lymphatic vessels in the wall of philtrum epiglottis form a larger lymphatic vessel, which crosses the thyroglossal periosteum and drains to the deep upper or deep middle cervical lymph nodes. The subglottic lymphatic vessels are fewer in number and drain to the pretracheal lymph nodes and perilaryngeal lymph nodes, then to the deep inferior cervical lymph nodes, and finally to the supraclavicular and superior mediastinal lymph nodes. There is Reinke’s connective tissue layer under the mucosa of the true vocal folds, and there are no lymphatic vessels under this layer, so lymph node metastasis is less likely to occur in vocal cancer, and the prognosis of radiotherapy is very good. Pathology The general classification of laryngeal cancer includes cauliflower type, nodular type, mass type and ulcerative type, etc. Epiglottis tumors are often cauliflower-like, subglottic tumors are mostly ulcerative, and tumors of vocal folds and ventricular zones are mostly small nodular masses. The histologic classification of laryngeal cancer is squamous cell carcinoma, followed by carcinoma in situ, adenocarcinoma and sarcoma are rare. The expansion and metastatic pathways of laryngeal cancer are as follows: 1. Direct expansion: Due to the obstruction of thyroid cartilage and its periosteum, laryngeal cancer mostly expands in the inner part of thyroid cartilage in the early stage, and then penetrates the cartilage and periosteum and invades into the soft tissues of the neck in the late stage. Tumor of epiglottis laryngeal surface can invade into the anterior epiglottic space and epiglottic valley; tumor of laryngeal compartment can easily invade into the pyriform fossa; tumor of vocal cord can easily invade into philtrum cartilage to paralyze the vocal cord; tumor of subglottic area can easily pass through the cricothyroid membrane to the thyroid gland. Lymphatic metastasis: Lymphatic metastasis of laryngeal cancer is related to the size of the tumor, the degree of pathological differentiation and the location of the tumor. Cervical lymph node metastasis of vocal cord cancer is rare, and the lymph node metastasis rate of supraglottic cancer is the highest. Most of the metastases are in the neck of the same side, and the contralateral or bilateral metastases are below 10%. 3.Bloodway metastasis: Early stage rarely occurs distant metastasis. Distant metastasis can be seen in cases of late stage and recurrence after treatment. It mainly metastasizes to lungs, liver and other places. The most common symptoms and signs of laryngeal cancer are as follows: 1. Hoarseness: it is the earliest symptom of cancer in the vocal folds, and the hoarseness is aggravated progressively; there is no hoarseness in the early stage of supraglottic cancer, and hoarseness occurs when the tumor invades the vocal folds or ventricular folds. Foreign body sensation in the throat: foreign body sensation in the throat or discomfort in swallowing is the first symptom of supravocal area cancer. 3.Difficulty in breathing: it is mostly seen in tumors in the lower or vocal folds, and the dyspnea often occurs in the middle or late stage. Coughing and coughing up blood: it is caused by respiratory tract infection due to the stimulation of trachea or tumor infection and necrosis after tumor enlargement. 5. Neck mass: the primary foci are mostly in the supraglottic area, most of the tumors are poorly differentiated and metastasize early, mostly to the lymph nodes in the middle and upper neck. Diagnosis and differential diagnosis The diagnosis of laryngeal cancer depends on the analysis of medical history, physical signs, imaging examination, various types of laryngoscopy and biopsy, etc. Early diagnosis is of great significance to the treatment and prognosis of patients. 1, clinical examination: through visual inspection and palpation, note whether there is any change in the shape of the larynx, whether there is any thickening of the cartilage and pressure pain; push the thyroid cartilage right and left with your hand to see if there is any friction sound of the thyroid ridge; when checking the neck, note that the cervical lymph nodes, especially the cervical upper and middle groups, and whether there is any enlargement of the lymph nodes in the anterior tracheal tube or the anterior laryngeal lymph nodes. 2, laryngoscopy: including indirect laryngoscopy, direct laryngoscopy, fiber-optic laryngoscopy. Generally, indirect laryngoscopy is commonly used. During the examination, attention should be paid to whether the structure of the larynx and its mobility are normal; if there is a mass, its size, scope, and the activity of the organ in which it is located should be examined; if it is proposed to be a tumor, a biopsy of pathological tissues should be done under indirect laryngoscopy. If indirect laryngoscopy is unsatisfactory, direct laryngoscopy or fiberoptic laryngoscopy should be used instead. 3.X-ray photo and CT examination: used to determine the scope of tumor tissue and its infiltration with surrounding tissue. Laryngeal ventriculography and oral barium can be used to check the situation of hypopharynx and esophageal inlet. Laryngeal cancer should be distinguished from laryngeal tuberculosis, vocal cord polyp, laryngeal keratosis, laryngeal leukoplakia and laryngeal papilloma. Radiotherapy The treatment of laryngeal cancer should start from the radical treatment and try to protect the patients’ function of voice, and make appropriate treatment plan according to the location of tumor, clinical stage, pathological type, and patients’ age, gender and general condition. Physicians of different disciplines should avoid the limitation of specialty and advocate mutual collaboration. Generally speaking, the general treatment principles are as follows: (1) Cancer of supraglottic area and glottic area: radiotherapy is appropriate for stage I, and preoperative radiotherapy plus partial laryngectomy or total laryngectomy can be done for stage II and III. (2) Total laryngectomy is usually performed for subglottic cancer. (3) Any person with cervical lymph node metastasis should have neck dissection. (4) Those whose pathology is adenocarcinoma should be mainly treated by surgery. (5) Advanced laryngeal cancer can be treated with chemotherapy or combined treatment with radiotherapy. At present, radiotherapy is one of the main means of treatment for laryngeal cancer, the advantage of which is that it can preserve the patient’s function of phonation, but the disadvantage is that the therapeutic effect is not satisfactory enough. (1) Indications of radiotherapy: radical radiotherapy for patients with stage I or II cancer in the vocal folds and supraglottic area, planned preoperative radiotherapy for patients with stage II, III or IV cancer in the vocal folds and supraglottic area, pathological type of poorly-differentiated cancer, residual or recurrent tumors after surgical resection, and palliative treatment for late-stage cases. (2) Relative contraindications to radiotherapy: radiotherapy is not suitable for those with extensive tumor necrosis, serious infection or edema of laryngeal tissues accompanied by respiratory difficulties, and radiotherapy is not suitable for those with local recurrence of the tumor after a regular full course of radiotherapy has been done. (3) Selection of radiation source: Generally, high-energy photon lines are used, such as 60Co γ line and 6-8MV X-ray of linear gas pedal. (4)Radiation technology: take the center irradiation such as head back extension position, whether the neck is fixed well has a great influence on the efficacy of radiotherapy, therefore, certain auxiliary tools should be used as much as possible to fix the head and neck in the treatment. In addition, because the front half of the neck cross section forms a slanting plane, in fact, the leading edge of the radiation field is overlapping, the dose distribution in the front and back parts of the larynx is uneven, so when the lesion is in the posterior 1/3 of the vocal folds or from the anterior part of the larynx all the way along the extension of the posterior part of the larynx, the use of wedge plate to improve the iso-dose distribution is very valuable, and the general use of wedge plate crossing of 300 is appropriate. (4) Radiation dose: split dose 1.8-2Gy/times, each time simultaneously irradiated both sides of the neck field, 1 time/day, 5 days/week. The total dose of radical radiotherapy is 65-75Gy/6.5-7.5 weeks (given according to the size of the lesion), preoperative radiotherapy is 50Gy/5 weeks, postoperative radiotherapy is 60-70Gy/6 weeks (60Gy/6 weeks for the lower neck), and palliative radiotherapy is 40-50Gy/4-5 weeks. (1) Cancer of suprasellar region: set up two cervical relative fields, including laryngeal and lymphatic drainage areas, with the upper border 1cm above the angle of the mandible, the posterior border to the transverse process of the cervical vertebrae or the spinal cord, the anterior border open, and the lower border flat at the lower edge of the cricoid cartilage. When irradiation reaches 40Gy, the posterior border should be moved forward to avoid the spinal cord and continue to irradiate the primary foci; if there is lymph node metastasis in the posterior cervical region, the posterior cervical region can be irradiated with additional dose by electronic wire. (2) Vocal cord cancer: two relative fields on the neck side, need not include lymph node drainage area. Centered on the vocal cord (0.5cm below the laryngeal node), the posterior border is the anterior border of cervical vertebrae, the anterior border exceeds the skin, the upper border is at the level of hyoid bone, and the lower border is at the lower edge of flat cricoid cartilage. (3) Cancer in the subvocalic region: it should include the primary focus and lymphatic drainage area, and there are two irradiation techniques: small dovecote field irradiation technique, . First set up single anterior field or anterior and posterior two-field butt-penetrating irradiation technique (the upper boundary depends on the extent of lesion invasion, and the lower boundary is close to the level of rongeur). (4) Postoperative radiotherapy: without lower cervical lymph node metastasis, the injection field method is the same as above; if there is lower cervical lymphatic metastasis, another lower anterior cervical split field irradiation is set up, and the upper boundary is connected with the lower boundary of the lateral cervical field. (5) Radiotherapy complications: during and after radiotherapy for laryngeal cancer, the most common complications are edema and local inflammation, and respiratory difficulty, which should be prevented before radiotherapy, such as tracheotomy or fistula for high-risk patients in advance, and be closely observed and handled during radiotherapy. Long-term sequelae include cartilage necrosis, skin ulceration, pharyngeal fistula or tracheo-esophageal fistula in trachea, etc. However, these usually appear when the dose is increased or combined with infection. [Prognosis] The therapeutic effect of laryngeal cancer is better, especially for stage I and II cases of cancer in the vocal fold area. The main factors affecting the prognosis are clinical stage of tumor, pathological type, tumor growth site, treatment mode and general condition of patients.