Stereotactic radiotherapy has additional limitations, continued Dr. Brackmann. Long-term tumor control rates are unknown. Many non-growing tumors have been treated, a practice that he condemns. If only growing tumors are treated, the control rate is likely to be less. Over the short term, 5% to 10% of tumors continue growing and require surgical removal. Complications of surgery are increased following stereotactic radiation.
Explore this issue:February 2008
Physicians at the House Ear Clinic have now had experience with 62 stereotactic radiotherapy failures. There is an increased risk to the facial nerve in surgery following failed radiotherapy. In nonirradiated tumors, there is a 98.6% anatomic preservation of the facial nerve. This falls to 82% when the surgery is necessary following irradiation failure, Dr. Brackmann noted.
Microsurgery may be used in combination with stereotactic radiotherapy, Dr. Brackmann continued; he suggested subtotal removal with microsurgery followed by stereotactic radiotherapy for tumors greater than 3 cm. At the House Clinic, total removal is planned but subtotal resection is performed if the facial nerve is at risk. This happens in about 5% of cases, he said.
The complication rate of stereotactic radiotherapy is still unknown in that complications may occur 20 to 40 years after radiotherapy, and low-dose radiation is more likely to induce tumors than high-dose radiation. There is an eightfold increase in benign intracranial tumors after low-dose radiation for tinea capitis. There is a 1,000-fold increase in acoustic neuromas after radiation for tonsils and adenoids. To date, there have been 20 reported cases of malignant induction or transformation, all fatal. These cases of malignant transformation may be just the tip of the iceberg, and you need to discuss these risks with patients, he said.
Dr. Brackmann concluded that microsurgery remains the established treatment of choice, particularly in younger patients. Stereotactic radiotherapy is a reasonable alternative, particularly in older patients, but the final place of this treatment is still being defined.
©2008 The Triological Society