Neutron radiotherapy for the treatment of locally advanced major salivary gland tumors

Background. Malignant salivary gland tumors are rare tumors of the head and neck region. The treatment of these tumors has generally consisted of surgical extirpation, with postoperative radiotherapy improving locoregional control and survival in patients with high risk tumors. Neutron radiotherapy has been found to be more efficacious than conventional radiotherapy in the setting of inoperable or subtotally resected salivary gland tumors. Methods. One hundred forty-eight patients with malignant salivary tumors of major salivary gland origin were treated at the University of Washington Medical Center with fast neutron radiotherapy between the years 1984 and 1995. One hundred twenty-eight patients were treated with curative intent, and of those, 120 patients had evidence of gross residual disease at the time of treatment. These patients constitute the main analysis of this paper. Of these patients. 19% had recurrent disease, 39% were initially seen with positive lymph nodes, and 11% had previously received full dose conventional radiotherapy. At the time of analysis, the median period at risk of survivors was 26 months. Results. The 5-year actuarial locoregional control rate for all patients with gross tumor treated with curative intent was 59%. A tumor size less than or equal to 4 cm was associated with an excellent locoregional control rate (80%), and cause-specific survival (73%) at 5 years compared with patients with larger tumors (35% and 22%, respectively, p <.001 in both cases). On univariate analysis, there appeared to be an advantage in locoregional control for patients with smaller sized tumors (less than or equal to 4 cm) who underwent an attempted surgical extirpation. Locoregional control was excellent (100%) in patients having a complete surgical resection of their tumors and undergoing postoperative neutron radiotherapy because of the presence of other high risk factors. Lymph node status at the time of treatment, base of skull involvement, and male sex were associated with the development of distant metastasis, with 52% of node positive patients developing distant metastases by 5 years, compared with 32% of node negative patients (p =.04). Conclusions. Neutron radiotherapy is an effective form of treatment for patients with high risk, locally advanced tumors of major salivary gland origin. An initial surgical resection appears beneficial in patients for whom such an approach is feasible. (C) 1999 John Wiley & Sons, Inc.