Can dysphagia aspiration related structures (DARS) be spared in patients with oropharyngeal cancers? Dosimetric evaluation in a prospective study of DARS optimized intensity modulated radiation therapy

Abstract

ABSTRACT Purpose: To evaluate the feasibility of sparing the dysphagia-aspiration-related structures (DARS) in various head and neck cancer sites treated with definitive DARS-optimized intensity modulated radiation therapy (IMRT) and concurrent chemotherapy. Materials and Methods: Target volumes, organs at risk, and in addition, individual DARS were delineated, including the superior, middle, and inferior pharyngeal constrictor muscles, supraglottic and glottic larynx, the base of the tongue, esophageal inlet muscles and cervical esophagus in 35 patients with head and neck squamous cell carcinoma. Volume-based dose constraints were applied to the DARS outside the planning target volume (PTV). An IMRT plan was then generated to limit doses to DARS without compromising PTV dose coverage. Results: Twelve (34.3%) patients had an oropharyngeal primary (OPX), 18 (51.4%) had a laryngeal, and 5 (14.3%) patients had hypopharyngeal primary. The mean dose to the DARS was 47.93 Gy for the entire group, while it was 54.6 Gy in oropharyngeal primaries and 44.4 Gy in laryngopharyngeal primaries. DARS mean dose of ≤45 Gy could be achieved in a significantly lesser number of patients with oropharyngeal primaries (P < 0.02). Similarly, DARS mean dose was 42.25 Gy in patients with N0 disease, 49.6 Gy with ipsilateral involved nodes, and 55 Gy with bilateral disease. Sparing of DARS was feasible when the volume of PTV was ≤150 cc (P < 0.025). Conclusion: Sparing of DARS structures appears to be challenging in patients with oropharyngeal cancers without compromising the dose to the PTVs while it is feasible in laryngopharyngeal cancers. DARS sparing is feasible when the PTV volume is < 150 cc and in patients with negative or unilateral nodal disease.