Comparison of Methods to Reduce Dose to Swallowing-Related Structures in Head and Neck Cancer

Abstract

Emerging data suggest that reduction of dose to the larynx and pharyngeal constrictor may lower the risk of swallowing complications such as long-term gastrostomy dependence and aspiration. Organ avoidance becomes difficult when the primary tumor or involved nodes are present at the level of the larynx. Fifteen patients with Stage III-IV squamous cell carcinoma of the head and neck with high-dose target volume at the level of the larynx (but not involving the glottic larynx) were planned with whole-field IMRT (WF-IMRT), as well as a low anterior neck field dynamically matched to an IMRT plan (D-SCLV). Plans were compared with respect to coverage of targets and sparing of normal tissues including the larynx, inferior pharyngeal constrictor (IPC), parotid, and cord. There was no significant difference between the two techniques in coverage of the high- or intermediate-dose planning target volumes (PTVs). Coverage of the elective nodal PTV was inferior with the D-SCLV technique, with a mean of 96.5% vs. 86.3% of the volume receiving the prescription dose (p = 0.001) compared with WF-IMRT plans. However, the D-SCLV technique significantly reduced mean dose to the larynx (43.7 vs. 46.7 Gy, p = 0.05) and IPC (39.1 vs. 46.1 Gy, p = 0.002). There was no significant difference in dose to the parotid or cord. Given the steep dose responses seen in studies examining the association between swallowing toxicity and dose to the larynx and IPC, dose reductions using the D-SCLV technique may be clinically significant.