Adenoid cystic carcinoma (ACC) is cancer most often occurring in the salivary glands. For head and neck ACC, the age-adjusted incidence rate is 4.5 cases per 100,000 individuals, occurring with a slight female predominance (60% vs. 40% in males). Cancer can also arise in other locations including the breast, skin, respiratory system, and reproductive organs. Adenoid cystic carcinoma is rare cancer with a high potential for recurrence and metastasis. The efficacy of current treatment options, particularly for advanced disease, is very limited. Recent whole-genome and exome sequencing has dramatically improved our understanding of ACC pathogenesis. Better genetic understanding will enable treatment with novel targeted agents and initial exploration of immune-based therapies with the goal of improving outcomes for patients with ACC.
Adenoid Cystic Carcinoma: Types of Treatment
Surgical removal of the tumour is the best treatment for ACC as long as it can be done safely and is likely to have a good outcome. During surgery, the surgeon will remove the tumour and an area of healthy tissue surrounding it called a margin. Surgery is considered the most successful if the margin removed during surgery is found to be “clean,” which means there is a minimum of 2 millimetres (mm) of cancer-free tissue surrounding the tumour. The extent of surgery will vary depending on the location of the tumour and the area of the body involved. Because ACC may frequently spread along nerves, the surgeon should examine and determine whether nerves are involved. Major nerves that are not involved should be identified and spared during surgery. Smaller branches of nerves should be analyzed to determine if cancer has spread to the space surrounding the nerve. For a later-stage tumour or one that significantly involves nerves, the surgeon should remove as much of the tumour as possible while sparing the organs and functions of the face.
Additional cancer treatment may be needed after surgery, called adjuvant therapy. Occasionally, it is not possible to remove ACC using surgery.
Side effects from surgery vary depending upon the surgical site. For example, surgery of the parotid salivary gland may damage facial nerves, which can cause the muscles in the face to droop. Sometimes, a facial nerve graft or other reconstructive procedure (plastic surgery) may be recommended to restore the function of the facial muscles after surgery to remove the tumour. Before surgery, talk with your health care team about the possible side effects from the specific surgery you will have and whether reconstruction will be needed.
2.External-beam radiation therapy
The most common type of radiation therapy is called external-beam radiation therapy, which is radiation given from a machine outside the body. A radiation therapy regimen, or schedule, usually consists of a specific number of treatments given over a set period. Radiation therapy is particularly effective for ACC as an adjuvant therapy by helping to eliminate any microscopic cancer cells that may remain in the body after surgery. Adjuvant therapy is cancer treatment given after surgery. Radiation therapy is not used preoperatively, meaning before surgery, for this disease. That is because many surgeons feel that the surgical wound heals better if radiation therapy is not given prior to surgery.
A specific method of external-beam radiation therapy, known as intensity-modulated radiation therapy (IMRT), allows for more effective doses of radiation therapy to be delivered while reducing the damage to healthy cells and causing fewer side effects. Before beginning radiation therapy for any head and neck cancer, people should receive a thorough examination from an oncologic dentist. Since radiation therapy can cause tooth decay, damaged teeth may need to be removed. People should also receive an evaluation from a speech pathologist with experience treating people with head and neck cancer. The speech pathologist can teach exercises that will help maintain the strength and flexibility of the muscles used during speech and swallowing.
Since radiation therapy is targeted to a specific area, the side effects will depend on where the radiation therapy was given. Generally, during head and neck treatments, people may experience a sore mouth and/or throat that can cause pain and difficulty in swallowing. They may also have a skin reaction or burn that causes some pain over time. Long-term side effects of radiation therapy vary with the sites involved, but they may include permanent loss of saliva, causing dryness of the mouth and deterioration of the teeth. In some cases, a drug to stimulate the parotid salivary gland and increase or restore saliva levels may be given. Currently, amifostine (Ethyol), a drug to protect tissues during radiation therapy, is being studied. Scarring or fibrosis, which is the hardening or thickening of the skin and muscles, may develop several months to years after radiation therapy and lead to problems with wound healing, neck stiffness, and trouble swallowing. Other long-term effects that can develop include accelerated narrowing of the carotid arteries, which supply the head and neck with blood. There may also be lower thyroid gland functioning, called hypothyroidism, which can be managed with thyroid hormone replacement medication.
3.Neutron and proton radiation therapy
Neutron therapy is a different form of radiation therapy that uses neutrons rather than x-rays. Compared with conventional radiation therapy, neutrons can deliver 20 times to 100 times more energy along their path length, causing much greater damage to the cancer cells. In certain instances, neutron radiation therapy may be the first treatment for ACC, particularly in areas of the body where it is difficult to perform surgery. However, neutron therapy carries more severe side effects than traditional radiation therapy, such as the severe sore mouth and/or throat and difficulty swallowing; therefore, it is generally used more often with people with an inoperable tumour or if the tumour recurs. Neutron radiation therapy has been tested on many different types of tumours, and its treatment for ACC has shown the greatest benefit. In certain instances, neutron radiation therapy may be the first treatment for ACC, particularly in areas of the body where it is difficult to perform surgery. However, neutron therapy carries more severe side effects than traditional radiation therapy, such as the severe sore mouth and/or throat and difficulty swallowing; therefore, it is generally used more often with people with an inoperable tumour or if the tumour recurs.
The advantage of proton therapy is the ability to better control where the radiation is delivered, greatly reducing the damage to normal healthy tissues that surround the tumour. However, proton therapy has not been extensively researched for use in ACC. Neutron and proton therapy are not widely available.
4.Endoscopic Endonasal Approach (EEA)
Adenoid cystic carcinomas of the sinuses and skull base can be approached directly using the Endoscopic Endonasal Approach (EEA). The minimally invasive approach allows surgeons to access the tumour through the natural corridor of the nose, without making an open incision. Surgeons then remove the adenoid cystic carcinoma through the nose and nasal cavities. EEA offers the benefits of no incisions to heal, no disfigurement, and a faster recovery time.
5.Therapies using medication
Systemic therapy is the use of medication to destroy cancer cells. This type of medication is given through the bloodstream to reach cancer cells throughout the body. Systemic therapies are generally prescribed by a medical oncologist. Systemic therapy is the use of medication to destroy cancer cells. This type of medication is given through the bloodstream to reach cancer cells throughout the body. Systemic therapies are generally prescribed by a medical oncologist. A person may receive 1 type of systemic therapy at a time or a combination of systemic therapies given at the same time. They can also be given as part of a treatment plan that includes surgery and/or radiation therapy. The medications used to treat cancer are continually being evaluated.
The types of systemic therapies used for ACC include:
- Targeted therapy
- Chemotherapy- Chemotherapy is the use of drugs to destroy cancer cells, usually by keeping the cancer cells from growing, dividing, and making more cells. A chemotherapy regimen, or schedule, usually consists of a specific number of cycles given over a set period. A patient may receive 1 drug at a time or combinations of different drugs given at the same time.
In general, chemotherapy is usually not used for ACC, as this type of cancer appears to be less responsive to chemotherapy than other types of cancer. Researchers are looking at the combination of chemotherapy and radiation therapy, but this is considered experimental for ACC.
- Targeted therapy- Targeted therapy is a treatment that targets the cancer’s specific genes, proteins, or the tissue environment that contributes to cancer growth and survival. This type of treatment blocks the growth and spread of cancer cells and limits damage to healthy cells. Not all tumors have the same targets. To find the most effective treatment, your doctor may run tests to identify the genes, proteins, and other factors in your tumor.
For ACC, clinical trials are researching the use of targeted therapy drugs called tyrosine kinase inhibitors (TKIs), such as lenvatinib (Lenvima), or sorafenib (Nexavar), taken as oral medication. This has shown to be a beneficial approach for a small proportion of people with ACC. Because of the general rarity of ACC and that current chemotherapy is of limited benefit.