Arytenoid-Sparing Intensity-Modulated Radiotherapy for Early-Stage Glottic Cancer

Purpose/Objective(s)

Standard treatment for early-stage glottic cancer with 3D-conformal radiotherapy (3D-CRT) offers durable long-term local control. Carotid-sparing intensity-modulated radiation therapy has become more widely used in an attempt to decrease toxicities. In this study, we demonstrate initial dosimetric results of a novel approach called arytenoid-sparing IMRT (AS-IMRT), which is aimed at reducing speech and swallowing toxicity.

Materials/Methods

We identified 26 patients with Stage 0-1 glottic cancer treated with radiation alone to 63 Gy in 28 fractions between 2017 and 2022. We selected two representative patients to assess dosimetric feasibility of AS-IMRT and compare organ-at-risk doses to 3D-CRT. We developed a novel target volume delineation protocol for bilateral and unilateral AS-IMRT. Arytenoid sparing was not done if tumor extended to the posterior 1/3 of the true vocal cord on that side, as determined by laryngoscopy. Carotid sparing was done bilaterally in all AS-IMRT plans. Clinical goals included planning target volume coverage D_95% > 95% and D_100% > 90%, spared arytenoid(s) D_mean< 40 Gy, and carotid D_mean < 20 Gy and D_max < 30 Gy.

Results

We generated AS-IMRT and 3D-CRT plans for one patient with bilateral arytenoid-sparing and one patient with unilateral (right) arytenoid-sparing. Table 1 describes the dose statistics when comparing 3D-CRT to AS-IMRT plans in these patients. Substantial sparing of the pharyngeal constrictor D_mean and the carotid D_max and D_mean occurred for both bilateral and unilateral AS-IMRT approaches. However, when attempting to spare only the right arytenoid, the clinical goal could not be met even on the spared side (right arytenoid D_mean 5225 cGy) due to proximity of the treated left arytenoid.

Conclusion

We have created a novel IMRT technique incorporating sparing of both arytenoids and carotids for early-stage glottic cancer. We have demonstrated dosimetric feasibility of this technique when compared to 3D-CRT, especially in the scenario of bilateral arytenoid sparing. We intend to complete comparative planning for the remainder of our cohort to optimize this technique and better understand its limitations. Ultimately, we plan on designing a prospective trial to evaluate whether this approach will lead to clinical benefits, including mitigating treatment-related dysphonia and dysphagia.