Dose reduction to dysphagia/aspiration-related structures (DARS) in patients receiving induction chemotherapy (IC) followed by concurrent chemoradiation therapy (CCRT) for locally advanced squamous cell carcinoma of the head and neck (LASCCHN)

Abstract

Radiation dose to dysphagia/aspiration-related structures (DARS) during definitive concurrent chemoradiotherapy (CCRT) is associated with chronic dysphagia and percutaneous endoscopic gastrostomy (PEG) tube dependency. Induction chemotherapy (IC) for locally advanced squamous cell carcinoma of the head and neck (LASCCHN) has been shown to decrease primary tumor and nodal size prior to CCRT, and we have begun to reduce gross tumor volumes (GTVs) for these patients based on post-IC scans. We evaluated dose reductions to DARS attributable to these reduced target volumes. Retrospective study of 41 consecutive LASCCHN patients treated with IC followed by CCRT. Patients were treated with docetaxel, cisplatin, and 5-fluorouracil (TPF) or another taxane-based regimen followed by CCRT with 70 Gy intensity-modulated radiation therapy (IMRT) with target volumes modified based on post-IC simulation scans. No dose constraints were placed on DARS. Patients’ pre-IC neck imaging scans were imported into our planning software, GTVs were contoured, and hypothetical pre-IC plans were generated. We compared dose volume histograms (DVHs) of the hypothetical pre-IC plans to the actual treatment plans for dose to DARS including the pharyngeal constrictor muscles and proximal esophagus, evaluating mean/max. dose, V50, and V60 with paired t tests. Late dysphagia was assessed via the University of Washington Quality of Life (UWQOL) survey and PEG tube dependency. Disease control was assessed with Kaplan–Meier analysis. Statistically significant dose reductions from pre-IC to post-IC scans were observed for superior pharyngeal constrictor (SPC) D mean (−1.1 Gy, P = 0.001), SPC D max (−1.1 Gy, P < 0.001), middle pharyngeal constrictor (MPC) D max (−1.5 Gy, P = 0.01), MPC V60 (−11.5 %, P = 0.001), total pharyngeal constrictor (TPC) D mean (−1.1 Gy, P < 0.001), TPC D max (−0.9 Gy, P < 0.001), TPC V60 (−2.5 %, P = 0.035), and PE V60 (−8.1 %, P = 0.049). In the 30 patients with UWQOL surveys ≥ 6 months posttreatment, mean swallowing score was 79 (scale 0–100). Two-year locoregional control (LRC) was 92 % (median follow-up 22 months). Modifying tumor target volumes post-IC in LASCCHN patients results in statistically significant, modest dose reduction to DARS.