A 10-year clinical outcome of radiotherapy as an adjuvant or definitive treatment for primary tracheal adenoid cystic carcinoma

Background To evaluate the role of radiotherapy (RT) as an adjuvant or definitive treatment in primary tracheal adenoid cystic carcinoma (ACC) for local tumor control and survival. Methods A retrospective chart review was performed in 22 patients treated with adjuvant or definitive RT for primary tracheal ACC at a single center between November 1994 and December 2008. Results Thirteen and 9 patients received adjuvant and definitive RT, respectively. Microscopic residual disease after surgery was pathologically reported in 11 patients. The median RT dose was 59.4 Gy for adjuvant and 74.4 Gy for definitive RT. The overall response rate for definitive RT was 77.8%. Six patients in the definitive RT group exhibited local progression (LP), whereas 14 patients in both groups exhibited distant metastasis. The most common recurrence site in cases of treatment failure was the lung parenchyma. The median follow-up duration was 123 months, and the 10-year overall survival (OS) rate was 54.2%. Although LP was the most common cause of death (4 patients), two-thirds of the patients treated with definitive RT lived for >5 years. The 5-year and 10-year LP-free survival (LPFS) rates in the definitive RT group were 66.7 and 26.7%, respectively. Patients with higher RT dose by brachytherapy boost had good 5-year OS, 83.3%, and showed no local progression till 5-years. Most of the RT-induced side-effects were mild and tolerable, but 2 patients died of tracheal stenosis without any tumor recurrence. Conclusions Adjuvant RT may be suitable for controlling microscopic residual disease, whereas definitive RT may yield appropriate long-term survival in >50% patients with unresectable tracheal ACC. Dose escalation should be considered to warrant long-term survival in definitive RT.