There is a paucity of information on the late effects seen after definitive radiotherapy for tracheal ACC; however, it should be acknowledged that high-dose thoracic radiotherapy has been associated with a finite risk of damage to the bronchi such as fistula or airway narrowing.21,22 Miller et al22 found that eight of 103 patients with unresectable non-small cell lung cancer (NSCLC) experienced symptomatic bronchial stenosis with doses ranging from 73.6 to 86.4 Gy; a dose-response relationship was suggested, supported by a 9% rate of stenosis at 74 Gy, 6% at 80 Gy, and 25% at 86 Gy. The majority of patients with bronchial stenosis received induction chemotherapy, and it is unclear whether that played a role in the development of airway toxicity. Interestingly, Kelsey et al22 reported that at doses >73.6 Gy, stenosis occurred within the bronchi but not in the trachea, suggestive of differential tolerances among structures that comprise the airway. In contrast, Jeremic et al25 documented delayed tracheal toxicity after doses of 70 Gy. Notably, most of the high-dose thoracic radiotherapy toxicity data have been gathered from patients with locally advanced NSCLC, of whom a majority receives concurrent or sequential chemotherapy.24 Lee et al25 also reported on late toxicities among patients with NSCLC treated with radiotherapy from 66 to 90 Gy, most with concurrent chemotherapy, and found no long-term toxicity in the 80-Gy group. At higher doses—82, 86, and 90 Gy—more patients experienced pulmonary late toxicity than those who did not, with a latency of 2 to 7 months. There are also phase 1 data for dose escalation with radiotherapy alone in NSCLC; Sura et al25 reported on radiotherapy for inoperable NSCLC where the majority of patients had stage III disease and doses were safely escalated to 84 Gy. This is of particular relevance to our report since both patients were also treated with radiotherapy alone. Finally, the QUANTEC (quantitative analysis of normal tissue effects in the clinic) report suggests that limiting the dose to 80 Gy or lower using standard fractionation may reduce the risk of central airway stenosis.27 Regarding the use of high-dose proton therapy, a dosimetric comparative study of IMRT, passive scattering protons, and intensity modulated protons for locally advanced lung cancer found that with intensity modulated proton dose could be escalated to 83.5 Gy while maintaining sparing of heart, lung, spinal cord, and esophagus.28 We hypothesize that as a result of using advanced techniques, long-term toxicity will be diminished.