Fast neutron radiation for recurrent pleomorphic adenomas of the parotid gland.

Between 1984 and 1989, six patients with recurrent pleomorphic adenomas of the parotid gland were treated with fast neutron radiotherapy. All of the patients in this series had one or more unfavorable prognostic features, which would predict suboptimal local tumor control rates with the utilization of standard surgical and adjuvant photon/electron radiation therapies. These prognostic features included multiply recurrent disease in three patients, known gross postoperative residual disease in one patient, extensive unresectable disease in one patient, and multiply recurrent disease plus gross postoperative residual disease in one patient. Patients had an average of three surgeries for recurrent adenomas before their neutron irradiation. The median period from the original diagnosis to the time of neutron treatment was 11 years, with a range of 1.3-32 years. With a median follow-up of 52 months, an overall local control rate of 100% was achieved. Only one grade III (European Organization for Research and Treatment of Cancer-Radiation Therapy Oncology Group scale) late complication occurred secondary to the neutron irradiation. Similar to their malignant counterparts, benign salivary gland neoplasms appear to display excellent response and control rates to treatment with fast neutron irradiation. Neutron irradiation of pleomorphic adenomas should be considered an appropriate therapeutic approach in situations, such as recurrent disease and postoperative gross residual disease, where one may be concerned about potential local failures with the use of standard surgical and radiotherapeutic modalities. Neutron radiation also carries a low risk of facial nerve damage, a consideration that may argue for limiting the extent of surgical resection of recurrent disease.