Volumetric modulated arc radiotherapy of the whole larynx, followed by a single affected vocal cord, for T1a glottic cancer: Dosimetric analysis of a case

Abstract

Abstract. Radiation therapy (RT) and endolaryngeal surgery are standard treatments for early-stage glottic cancer. They have closely matched oncological outcomes; however, it is debatable which method is superior in terms of functional outcomes. Several dosimetric studies have demonstrated that, compared with conventional RT, intensity-modulated RT (IMRT) reduces unnecessary radiation of the adjacent normal tissues, including the carotid artery and thyroid gland. However, RT targets the whole larynx, whereas endolaryngeal surgery is a highly focused treatment involving the en bloc resection of a tumor with safety margins. For T1a glottic cancer, in which the tumor is limited to one vocal cord, the technical feasibility of targeting IMRT on the single vocal cord affected has been investigated; however, the clinical feasibility and the possibility of inferior local control remain to be elucidated. In the present case study, IMRT was used to treat the whole larynx first, and then to treat a single vocal cord. The patient in the present study had T1a glottic cancer, and received volumetric modulated arc therapy with a total dose of 63 Gy/28 fractions. The first treatment phase (40.5 Gy/18 fractions) targeted the whole larynx to eliminate subclinical disease. The second treatment phase (22.5 Gy/10 fractions) targeted only the involved vocal cord. During this treatment phase, the exposure of the non-involved right vocal cord, the right carotid artery and the thyroid gland to the radiation was lower compared with the continuation of the initial treatment approach. These findings suggested that changing the target volume from the whole larynx to the affected vocal cord during the course of IMRT is feasible for T1a glottic cancer, and that it may reduce functional side effects while maintaining oncological outcomes.

Oncologic Outcomes of T1–T2N0 Glottic Cancer Treatment: Single Center Experiences of 417 Patients Over 20 Years

“…Recently, one study showed an interesting outcome that single vocal cord irradiation using IMRT improved voice quality compared to conventional techniques [34]. IMRT reduced the RT dose to the contralateral vocal cord in several dosimetric studies [35][36][37]. In addition, the necessity of adjuvant RT may result in poorer functional outcomes.…”

Dose-Volume Comparison of IMRT and PSPT Treatment Plans for Early-Stage Glottic Cancer

“…Consideration of advanced RT technologies with minimal impact to surrounding normal tissues is worthwhile in such cases. There are many reports on IMRT for early-stage glottic cancer [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21], but no reports have yet detailed the dose distribution characteristics of PT for early-stage glottic cancer. In this study, we therefore aimed to clarify the dose distribution between IMRT and PT for early-stage glottic cancer and examined the usefulness of PT for early-stage glottic cancer.…”