Adenoid Cystic Carcinoma
Background
Adenoid cystic carcinoma (ACC or AdCC) is a rare form of adenocarcinoma (any cancer arising from glandular tissues). ACC can exist in many different body sites. It most often occurs in the areas of the head and neck, in particular the salivary glands, but has also been reported in the breast, lacrimal gland of the eye, lung, brain, bartholin gland, and the trachea. As compared with most other carcinomas, ACC has a slow course with a survival rate of 89 percent at 5 years. However, it is a chronic condition; tumors progess persistently and often recur, resulting in a survival rate of only 40% after 15 years. Remote metastases is also a feature of this type of cancer and can occur even a decade or more after initial treatment of the primary tumor, with the most common sites of metastasis being the lung, bone and viscera.
Women are more likely to develop this disease than men by a ration of 3 to 2.
Causes
No definitive genetic or environmental causes have been identified. However, there is some evidence that the p53 tumor suppressor gene (a gene that limits cell growth by monitoring the rate at which cells divide) is inactivated in advanced and aggressive forms of the disease.
Symptoms
Symptoms vary depending on the site and origin of the tumor. Lesions of the salivary glands present as painless, slow-growing masses in the mouth or face. Tumors of the lacrimal gland may cause proptosis (bulging of the eye) and changes in vision. Those arising in the tracheobronchial tree may present with respiratory symptoms, such as dyspnea (shortness of breath), while the presence of tumors in the larynx may lead to changes in speech. Pain, numbness and/or nerve paralysis may accompany advanced tumors due to the tendency of ACC to infiltrate and spread along nerves.
Diagnosis
Diagnosis is made through microscopic evaluation of the tumor cells, which are obtained via a biopsy.
ACC tumors have a distinctive pattern in which abnormal bundles of epithelial cells surround and/or infiltrate ducts or glandular structures within the affected organ. Recurrences of ACC are usually identified by radiographic imaging techniques, primarily MRI and CT.
Treatment
The treatment of ACC depends on the size and location of the tumor, whether the cancer has spread, and the person’s overall health. The standard treatment for ACC is surgical removal of the malignant tissue. During surgery, the surgeon will remove the tumor and an area of tissue surrounding it. The presence of clean margins, meaning a minimum of 2 mm of tissue that is cancer-free surrounding the tumor, signals total tumor removal and gives the best chance that cancer will not recur at that site. Side effects from surgery vary depending upon the site. In the case that surgery involves the parotid gland, a concern is facial nerves may be damaged or severed, which can cause the muscles in the face to droop. Sometimes, a facial nerve graft may be used to restore function of the facial muscles after removal of the tumor.
Traditionally, ACCs of the sinuses and skull base were approached through wide incisions in the face, side or top of the head (standard skull base approaches). These procedures can be very morbid for the patient and generally have long recovery times.
At MINC, adenoid cystic carcinomas of the sinuses and skull base can be directly approached through endoscopic endonasal approach (EEA). This state-of-the-art, minimally invasive surgical procedure uses the nose as a natural corridor to reach these lesions. There are no incisions in the skin of the face or head.
Surgery is usually followed by postoperative radiotherapy. After an endoscopic endonasal resection of the tumor, patients do not need to wait several weeks to heal from the surgery before any radiotherapy is performed. Patients can receive radiation treatment sooner.
Neutron therapy, is a different form of radiation therapy, is also used to treat ACC. Compared with conventional radiation therapy, neutrons can deliver 20 to 100 times more energy along their path length, causing much greater damage to the cancer cells. Neutron radiation therapy has been tested on many different types of tumors, with salivary gland tumors—in particular ACC—showing the greatest benefit. In certain instances, it may be the treatment of choice for ACC, particularly in areas of the body where it is difficult to perform surgery. However, neutron therapy carries more severe side effects than conventional radiation therapy, such as severe sore mouth and/or throat and difficulty swallowing, and therefore is used more often in cases where the disease is inoperable or recurrent.
There are currently no chemotherapy treatments proven to be effective in treating ACC. However, the protracted course of the disease makes it an ideal candidate for research, and several clinical trials for chemotherapy medications are underway.
Prevention
There is no known way to prevent the development of adenoid cystic carcinoma.