Radiotherapy for Tracheal-Bronchial Cystic Adenoid Carcinomas

Primary tracheal-bronchial adenoid cystic carcinoma (thoracic adenoid cystic carcinoma; TACC) is a rare and aggressive malignant tumour. Radiotherapy results have not been previously individualised in this setting.

Records of 31 patients with TACC (74% tracheal and 26% bronchial) who received radiotherapy between February 1984 and September 2014 were retrospectively analysed.

Surgical removal of the primary tumour was carried out for most (71%) patients, and 13/22 (59%) had R1 or R2 (1/22) margins. The mean tumour size was 4.1 cm, 10 (32%) had associated lymph node involvement and 13 (41%) had perineural invasion (PNI). Adjuvant and definitive radiotherapy were delivered for 22 (71%) and nine patients, respectively. The mean delivered dose was 62 Gy (40-70 Gy) and eight patients had a radiotherapy boost (mean 19 Gy, range 9-30 Gy, two with endobronchial brachytherapy). At a median follow-up of 5.7 years, the 5 year overall survival and progression-free survival (PFS) rates were 88% and 61%, respectively. There were three local relapses and 10 metastatic relapses (mean delay 3.2 years), resulting in 5 year local and metastatic relapse rates of 10% and 26%, respectively. The prognostic factors in the univariate analysis for both decreased overall survival and PFS were: age ≥50 years (hazard ratio 6.2 and 3.8) and the presence of PNI (hazard ratio 10.3 and 4.1); and for PFS only: a radiotherapy dose ≤ 60 Gy (hazard ratio 3.1). Late toxicities were: tracheotomy due to symptomatic tracheal stenosis (n = 5), G3 dyspnoea (n = 4), hypothyroidism (n = 5) and pericarditis (n = 4).

Radiotherapy dose may affect local control and the presence of PNI should be considered as an adverse prognostic factor. TACC irradiation conferred good local control rates, when comparing these results with historical series.