Radiotherapy for advanced adenoid cystic carcinoma: neutrons, photons or mixed beam?

Purpose: To compare retrospectively radiotherapy with neutrons, photons, an d a photon/neutron mixed beam in patients with advanced adenoid cystic carc inoma of the head and neck. Local control, survival, distant failure, and c omplications were analyzed. Materials and methods: Between 1983 and 1995, 75 patients with inoperable, recurrent, or incompletely resected adenoid cystic carcinoma of the head an d neck received radiotherapy that consisted of either fast 14.1 MV DT neutr ons (median dose 16 neutron Gy), linac-based photon irradiation (median dos e 64 photon Gy), or both (median dose 8 neutron Gy and 32 photon Gy). Follo w-up ranged from 1 to 160 months (median 51 months), and the surviving pati ents had a minimum follow-up of 3 years at the time of analysis. Results: The actuarial 5-year local control was 75% for neutrons, and 32% f or both mixed beam and photons (P = 0.015, log-rank). This advantage for ne utrons in local control was not transferred to significant differences in s urvival (P > 0.1). The survival is dictated by the tumor diseases due to di stant metastases occurring in 29 (39%) of the 75 patients. Positive lymph n odes were the only significant factor (P = 0.001) associated with the devel opment of distant metastases although negative lymph nodes did not predict absence of distant metastases, but predicted a delay of occurrence. In mult ivariate analysis postoperative radiotherapy (P = 0.003) and small tumor si ze (P = 0.01) were associated with high local control, while primary therap y (P = 0.006) and negative lymph nodes (P = 0.01) were associated with long er survival. While acute toxicity was similar in all three radiotherapy gro ups, severe late grade 3 and 4 toxicity tended to be more prevalent (P > 0. 1) with neutrons (19%) than with mixed beam (10%) and photons (4%). Conclusion: Fast neutron radiotherapy provides higher local control rates t han a mixed beam and photons in advanced, recurrent or not completely resec ted adenoid cystic carcinoma of the major and minor salivary glands. Neutro n radiotherapy can be recommended in patients with bad prognosis with gross residual disease (R2), with unresectable tumors, or inoperable tumors. The type of radiation does not impact survival, which is dominated by the high number of distant metastases. (C) 2001 Elsevier Science Ireland Ltd. All r ights reserved.