A treatment planning method to avoid the larynx and eliminate the match-line in the treatment of head and neck cancer with intensity-modulated radiation therapy

Purpose This study aims to investigate a new planning method that avoids the match-line while maintaining larynx protection as in split field intensity-modulated radiation therapy (IMRT) and to evaluate the potential match-line dose variations with split IMRT. Methods/materials The new planning method, referred to as selective extended-field IMRT, selected anterior and anterior oblique fields to treat the entirety tumor volumes while restricting other IMRT fields from treating the tumor volumes below the larynx. Five patients with nasopharyngeal cancer, who underwent conventional extended-field IMRT, were replanned using the selective extended IMRT and split-field IMRT techniques. Results When treatment goals to the target volumes were met, selective extended-field IMRT resulted in an average mean larynx dose of 28.6+/-1.4 Gy, as compared with 41.9+/-10.6 and 29.3+/-5.6 Gy for extended-field and split-field IMRT, respectively. For other organs at risk, there were no significant dose differences (p>0.05) among three planning methods. Conclusions Selective extended-field IMRT achieves comparable tumor volume coverage as the conventional extendedfield IMRT and comparable larynx sparing as split-field IMRT while eliminating field matching.