Comprehensive head and neck radiotherapy dose-volume constraints do not apply to smaller volumes

To investigate the impact of definitive radiation therapy (RT) in the management of early glottic cancer on clinical RT-induced dysphagia (RID) and carotid vasculopathy (RICV).

This is a single-institution retrospective study. From January 1997 to 2010, 253 patients, with early glottic cancer, underwent RT with (60)Co or LINAC-6 MV photons. RT fields with wedge pair and daily 5-mm bolus were applied in all patients treated with 6-MV photons to avoid under-dose of the anterior laryngeal structures. The whole larynx (LX), pharyngeal constrictors (PCs), and carotid arteries (CA) were contoured and dose-volume histograms (DVHs) were generated to assess the delivered dose. The median age of patients was 65 years (range; 28-93), Caucasians were 80%, males were 87%, and 23% had T2 lesions.

After a median follow-up of seven years (range; 1.5-12), the median dose and fraction size delivered to the LX were 63 and 2.25 Gy, respectively. The mean doses to the LX, PC, and CA were 57 Gy delivered to 34 cm(3), 54 Gy to 15 cm(3), and 60 Gy to 4 cm(3), respectively. The LX, PC and CA V60 and V65 were (77 and 71), (70 and 52) and (84 and 51), respectively. Patients with acute dysphagia grades 1, 2, and 3 or more were 81, 19%, and zero, respectively; none had clinically RID or RICV.

Small-volume RT up to 67.5 Gy at 2.25 Gy per fraction, is not a predictor of RID or RICV. Separate delineation of the aforementioned critical structures, as well as others, may better identify dose tolerances to maintain function and further prioritize the importance of structures in RID and RICV.