There are three main pairs of salivary glands: parotid, sublingual and submandibular and over 600 minor salivary glands. Most salivary gland tumours are benign, 3 out of 4 tumours that arise in the parotid glands are benign.
Facts and figures of salivary gland cancer
Salivary gland cancer is very rare, about 690 new cases are diagnosed each year in the UK, but this is increasing. There is a very slightly higher incidence in men; male to female ratio is approximately 1.02:1. Age related, most common in the 50-70 years age group.
Risk factors include smoking, radiotherapy for a previous head and neck cancer, exposure to radioactive sources, first degree relative having been diagnosed with salivary gland cancer and possibly HPV exposure. 80% of these tumours arise in the parotid glands and are usually mucoepidermoid tumours, another 10% arise in the submandibular glands and the other 10% occur in the sublingual and minor salivary glands. Other tumour types include acinic carcinoma, adenoid cystic and adenocarcinoma with a small number of mixed type.
Salivary gland cancer symptoms
- A lump or swelling near the jaw – this is the most common symptom at presentation.
- Lump/swelling in the mouth or neck.
- Drooping of one side of the face (facial palsy).
- Pain/discomfort in the area.
- Difficulty in swallowing (dysphagia).
- Difficulty with fully opening the mouth.
Diagnosis of salivary gland cancer
Investigations may include:
- Physical examination.
- Blood tests.
- X-ray of jaw and teeth.
- Fine needle aspiration (FNA)- a thin needle is used to collect cells from the lump/swelling for analysis.
- MRI scan.
- Ultra sound scan.
Treatment of salivary gland cancer
Depends on several factors:
- The type of salivary gland cancer.
- The position of the tumour.
- The stage of the cancer.
- Impact of treatment on speech, chewing and swallowing.
- General health.
Surgery is the most common treatment for salivary gland cancer as it is effective in early stage disease. It will depend on the size and possibly the depth of the tumour and whether the lymph nodes are known or thought to be involved. During surgery some neck nodes nearest to the tumour may be removed but if disease is found in the neck nodes then all of the nodes on one or both sides of the neck may be removed to reduce the risk of recurrence (neck dissection). Post-operative radiotherapy may be advised to reduce possible recurrence.
Radiotherapy may be effective and can sometimes be the main treatment particularly if surgery is inappropriate due to the patient’s general health or position of the tumour inhibits complete excision. Also, surgery carries a high risk of facial disfigurement and therefore some patients will refuse surgery and request radiotherapy as an alternative.
Head and neck radiotherapy can have unpleasant chronic side effects which includes a dry mouth (xerostomia- most common late side effect) due to damage to the salivary glands which stops saliva production. However, trials have proved that in suitable cases where Intensity Modulated Radiotherapy (IMRT) has been used to treat head and neck cancers the incidence of xerostomia is significantly reduced as the treatment can be very accurately targeted to the area requiring treatment and sparing healthy surrounding tissue. In patients with salivary gland tumours, the affected salivary gland will need to be treated and therefore it is important to minimise dose to the other salivary glands.
Image guided radiotherapy (IGRT) also enables the radiotherapy to be precisely delivered to the intended area which reduces potential radiation dose to healthy tissues and allows the radiography team to monitor any changes in the patients shape. This is important as head and neck patients often lose weight during treatment which can affect the aligning of the radiotherapy treatment. In some cases, it may be necessary to make a new headshell and replan the patient’s radiotherapy treatment.
It is important to achieve precise alignment for accuracy in delivering radiotherapy, therefore in most cases it is necessary for a ‘headshell’ to be produced. This is achieved by using a specialised thermoplastic material which can be heated in warm water and then is laid over the patient’s face to form an accurately fitting customised shell which can then be used for the planning CT scan and for all the radiotherapy treatments. It is a painless procedure which is clearly explained by the radiographers prior to the procedure.
Chemotherapy is rarely used as it is not as effective as surgery or radiotherapy. However, it may be used if the disease has spread to other parts of the body or recurred after surgery or radiotherapy.