Salivary gland cancer
How common is it?
Cancers of the salivary glands (parotid gland, submandibular glad, sublingual gland and minor salivary glands) are relatively uncommon, occurring in around 1-10 per 100,000 people in the population. In addition, they are a wide spectrum comprising of multiple subtypes of cancer, with different treatment modalities available. Benign tumours are much more common, however distinguishing between these and cancer without surgical removal and testing is notoriously difficult.
What are the symptoms?
The parotid gland located behind the ear and symptoms of cancer include a swelling in the region, redness or skin changes in the region, a lump in the neck, deviation or weakness of the face or inability to close the eyelids and difficulty opening the mouth. The submandibular salivary gland is located below the jawbone and symptoms of cancer include a lump or pain the region, a lump in the neck and numbness or weakness on one side of the tongue. The sublingual gland is located under the tongue and symptoms of cancer include a swelling here, pain, restriction in movement or numbness of the tongue and a neck swelling. Minor salivary glands are tiny gland present in the mouth, palate and upper throat, with cancers presenting as painful or painless swellings, a lump in the neck, difficulty swallowing or opening the mouth.
What causes it?
Most salivary gland cancers are sporadic – they occur in patients who do not have any genetic abnormalities inherited from their parents – with no exposure or risk factors. It is believed that certain types of salivary gland cancer are associated with smoking, Epstein-Barr virus infection, radiation exposure and industrial pollutants from silica, nickel and rubber manufacturing; however none of these have been proven unequivocally.
How do you diagnose it?
Evaluation of these cancers involves two parts. The first is fine needle aspiration, which is a biopsy performed with a fine needle, where cells from are studied to determine the type of cancer. The second part is imaging of the cancer with CT, MRI or PET scan to assess the extent to which spread has occurred. Unfortunately needle tests are not 100% accurate, meaning that the diagnosis may change after the tumour is removed and sent for pathological testing. Based on the needle test and the imaging, the best possible treatment for your cancer is determined.
How do you treat it?
The vast majority of salivary gland tumours are treated with surgery. The goal of surgery is to completely remove the cancer with a rim of uninvolved tissue (known as a ‘margin’), and remove the draining lymph nodes in the neck. The complexity of surgery revolves around the critical structures in close proximity to these structures; the parotid gland is traversed by the facial nerve which controls all the muscles of facial expression on one side, which the submandibular and sublingual glands are located close to the marginal mandibular nerve (which controls lower lip movement), lingual nerve (which is responsible for sensation on one side of the tongue) and the hypoglossal nerve (which is responsible for movement of one side of the tongue).
Intra-operative nerve monitoring is an important part of the operation that prevents accidental injury to the facial nerve. In spite of this, around 16% of parotid gland cancers require sacrifice of at least part of the facial nerve in order to completely remove the tumour, resulting in facial weakness. A major part of treatment when the facial nerve is sacrificed is immediate facial nerve reanimation, which is either reconstruction of the facial nerve when possible, or an additional part of the operation to restore facial function when the nerve cannot be reconstructed. This is performed in only a handful of centres in the country.
Early cancers are sufficiently treated with only surgery, however advanced tumours may require additional radiotherapy, with or without chemotherapy. Cancers that cannot be removed completely with surgery are treated with radiotherapy alone or with chemotherapy.
Is it curable?
Most of these cancers are curable when treated early and appropriately. Multi-disciplinary care (surgery, radiation oncology, medical oncology, pathology and radiology) is essential to treat these cancers, as they are both rare and complex. Even when these tumours are advanced and they have spread to other organs, newer treatment options (chemotherapy and immunotherapy) have shown promise in specific patient groups.
What does the road to recovery look like?
The extent of your treatment will determine how long it takes you to recover. Surgery for an early tumour may take two weeks to recover from while a major surgery following by radiotherapy and chemotherapy may take months to completely recover from. It is important to think of your treatment as a marathon rather than a sprint, and take help from those around you, whether they are medical professionals, or friends and family. The team involved in your rehabilitation may include the speech and swallowing therapist, the dental team, the physical therapist and the pain specialists. Follow-up after treatment is crucial – this is to not only assess your recovery, but also to check for recurrence. Expertise in facial reanimation is essential when the cancer has involved your facial nerve: long-term problems with chewing, speaking and social functioning can be prevented by early and aggressive surgical and non-surgical treatment