Therapy strategies for locally advanced adenoid cystic carcinomas using modern radiation therapy techniques

The authors evaluated whether modern photon techniques, such as stereotactic fractionated radiation therapy (FSRT) or intensity-modulated RT, outweighed the biologic advantages of high-linear-energy transfer RT in the treatment of patients with locally advanced adenoid cystic carcinomas (ACC) that infiltrated the skull base or the orbit.

Between June 1995 and December 2003, 63 patients with ACC were treated with modern RT techniques at the University of Heidelberg. The treatment results achieved with modern photon techniques alone were compared with the results achieved with combined photon RT and a carbon ion boost. Twenty-nine patients (Group A) were treated with a combination of photon RT and a carbon ion boost. Thirty-four patients (Group B) received photon RT alone.

The median follow-up was 16 months for Group A and 24 months for Group B. Locoregional control rates at 2 years and 4 years were 77.5% and 77.5% for Group A and 72.2% and 24.6% for Group B, respectively (P = 0.08; log-rank test). Disease-free and overall survival rates at 2 years/4 years were 71.5%/53% and 86.6%/75.8% for Group A and 69.2%/23% and 77.9%/77.9% for Group B, respectively. Rates for severe late toxicity were < 5% for both groups.

Modern RT techniques allowed the safe delivery of high target doses to patients with locally advanced ACC. Late toxicity rates were kept lower compared with the historic neutron therapy data. A combination of modern photon RT and carbon ion RT seemed to be advantageous, with a trend toward higher locoregional control rates compared with modern photon RT alone.