Desmoid tumors: local control and patterns of relapse following radiation therapy.

Desmoid tumors are benign neoplasms, arising from musculoaponeurotic tissues, which tend to be locally infiltrative, resulting in a high rate of local recurrence following surgical resection. Nineteen patients with desmoid tumors underwent radiation therapy at the University of California, San Francisco, between 1970 and 1980. Fifteen patients were referred with local recurrence following one or more surgical resections. Three patients were referred for initial radiation therapy with unresectable tumors, and one patient received planned postoperative irradiation following subtotal tumor resection. At the time of treatment, 8 patients had nonresectable disease measuring greater than 10 cm. Five patients had residual tumor masses measuring 4 to 6 cm, and six had only microscopic disease following resection. The majority of patients were treated to a tumor dose of 50-55 Gy at 1.6 to 1.8 Gy per fraction. With a median follow-up of 8 years, 13 patients remained free of recurrent disease following radiation therapy. The 5 year relapse free survival was 72% with 10 patients continuing to be free of disease 5 to 11 years following therapy. Local control was not related to the amount of disease present at the time of treatment. Of the 6 patients who developed recurrent disease, only 1 patient had a true in-field recurrence. Four patients recurred at the margin of the radiation field 1 to 5 years following therapy. Of these four patients, 3 were successfully salvaged while 1 died as a result of tumor extension into a major vessel. One patient with an extensive mesenteric mass did not respond to therapy and died 1 month post irradiation. The patient with the in-field recurrence and 1 patient with a marginal recurrence were successfully treated with combination chemotherapy. Moderate dose radiation therapy to desmoid tumors can result in lasting local control when surgical resection is not possible. Post operative radiation can improve the rate of local control for patients with a high risk of recurrence. As desmoid tumors tend to be locally infiltrative, fields must be very generous to prevent marginal recurrence. Systemic chemotherapy offers an alternative to ablative surgery in the event of local failure following radiation therapy.