Radiotherapy for advanced adenoid cystic carcinoma: neutrons, photons or mixed beam?
OBJECTIVE
To compare retrospectively radiotherapy with neutrons, photons, and a photon/neutron mixed beam in patients with advanced adenoid cystic carcinoma of the head and neck. Local control, survival, distant failure, and complications were analyzed.


METHODS
Between 1983 and 1995, 75 patients with inoperable, recurrent, or incompletely resected adenoid cystic carcinoma of the head and neck received radiotherapy that consisted of either fast 14.1 MV DT neutrons (median dose 16 neutron Gy), linac-based photon irradiation (median dose 64 photon Gy), or both (median dose 8 neutron Gy and 32 photon Gy). Follow-up ranged from 1 to 160 months (median 51 months), and the surviving patients 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% for both mixed beam and photons (P = 0.015, log-rank). This advantage for neutrons in local control was not transferred to significant differences in survival (P > 0.1). The survival is dictated by the tumor diseases due to distant metastases occurring in 29 (39%) of the 75 patients. Positive lymph nodes were the only significant factor (P = 0.001) associated with the development of distant metastases although negative lymph nodes did not predict absence of distant metastases, but predicted a delay of occurrence. In multivariate analysis postoperative radiotherapy (P = 0.003) and small tumor size (P = 0.01) were associated with high local control, while primary therapy (P = 0.006) and negative lymph nodes (P = 0.01) were associated with longer survival. While acute toxicity was similar in all three radiotherapy groups, 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%).


CONCLUSIONS
Fast neutron radiotherapy provides higher local control rates than a mixed beam and photons in advanced, recurrent or not completely resected adenoid cystic carcinoma of the major and minor salivary glands. Neutron 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.
Huber
P E
PE
Department of Radiation Oncology, University of Heidelberg, Heidelberg, Germany.
Debus
J
J
Latz
D
D
Zierhut
D
D
Bischof
M
M
Wannenmacher
M
M
Engenhart-Cabillic
R
R
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D003528:Carcinoma, Adenoid Cystic / Q000401:mortality / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009502:Neutrons / Q000627:therapeutic use*; D017785:Photons / Q000627:therapeutic use*; D016016:Proportional Hazards Models; D011878:Radiotherapy / Q000009:adverse effects; D012189:Retrospective Studies; D012468:Salivary Gland Neoplasms / Q000401:mortality / Q000532:radiotherapy*; D016019:Survival Analysis; D016896:Treatment Outcome