NEUTRON VERSUS PHOTON IRRADIATION FOR UNRESECTABLE SALIVARY-GLAND TUMORS - FINAL REPORT OF AN RTOG-MRC RANDOMIZED CLINICAL-TRIAL

Purpose: To compare the efficacy of fast neutron radiotherapy versus c onventional photon and/or electron radio-therapy for unresectable, mal ignant salivary gland tumors a randomized clinical trial comparing was sponsored by the Radiation Therapy Oncology Group in the United State s and the Medical Research Council in Great Britain. Methods and Mater ials: Eligibility criteria included either inoperable primary or recur rent major or minor salivary gland tumors. Patients were stratified by surgical status (primary vs. recurrent), tumor size (less than or gre ater than 5 cm), and histology (squamous or malignant mixed versus oth er). After a total of 32 patients were entered onto this study, it app eared that the group receiving fast neutron radiotherapy had a signifi cantly improved local/regional control rate and also a borderline impr ovement in survival and the study was stopped earlier than planned for ethical reasons. Twenty-five patients were study-eligible and analyza ble. Results: Ten-year follow-up data for this study is presented. On an actuarial basis, there continues to be a statistically-significant improvement in local/regional control for the neutron group (56% vs. 1 7%, p = 0.009) but there is no improvement in overall survival (15% vs . 25%, p = n.s.). Patterns of failure are analyzed and it is shown tha t distant metastases account for the majority of failures on the neutr on arm and local/regional failures account for the majority of failure s on the photon arm. Long-term, treatment-related morbidity is analyze d and while the incidence of morbidity graded ''severe'' was greater o n the neutron arm, there was no significant difference in ''life-threa tening'' complications. This work is placed in the context of other se ries of malignant salivary gland tumors treated with definitive radiot herapy. Conclusions: Fast neutron radiotherapy appears to be the treat ment-of-choice for patients with inoperable primary or recurrent malig nant salivary gland tumors.