Thyroid-optimized and thyroid-sparing radiotherapy in oral cavity and oropharyngeal carcinoma: A dosimetric study

Anna K Wu; Nicholas J Damico; Erin Healy; Michael Z Kharouta; Ghazal Khandel; Alok Deshane; Jennifer Sipos; Jacob Eckstein; Wesley Zoller; Ashlee Ewing; Stella Ling; Jessica Wobb; Darrion Mitchell; John Grecula; Sachin Jhawar; Eric Miller; Mauricio Gamez; Virginia Diavolitsis; Dukagjin Blakaj; Aashish D Bhatt

doi:10.1016/j.tipsro.2021.10.003

Thyroid-optimized and thyroid-sparing radiotherapy in oral cavity and oropharyngeal carcinoma: A dosimetric study

Tech Innov Patient Support Radiat Oncol. 2021 Nov 1:20:28-34. doi: 10.1016/j.tipsro.2021.10.003. eCollection 2021 Dec.

Authors

Anna K Wu¹, Nicholas J Damico², Erin Healy³, Michael Z Kharouta², Ghazal Khandel², Alok Deshane¹, Jennifer Sipos⁴, Jacob Eckstein³, Wesley Zoller³, Ashlee Ewing³, Stella Ling³, Jessica Wobb³, Darrion Mitchell³, John Grecula³, Sachin Jhawar³, Eric Miller³, Mauricio Gamez³, Virginia Diavolitsis³, Dukagjin Blakaj³, Aashish D Bhatt²

Affiliations

¹ Case Western Reserve University School of Medicine, Cleveland, OH, USA.
² Department of Radiation Oncology, University Hospitals Seidman Cancer Center, Cleveland, OH, USA.
³ Department of Radiation Oncology, Ohio State University, Columbus, OH, USA.
⁴ Department of Endocrinology, Ohio State University, Columbus, OH, USA.

Abstract

Background: Radiation-induced hypothyroidism is a common toxicity of head and neck radiation. Our re-planning study aimed to reduce thyroid dose while maintaining target coverage with IMRT.

Methods: We retrospectively identified patients with oral-cavity (n = 5) and oropharyngeal cancer (n = 5). Treatment plans were re-optimized with 45 Gy thyroid mean dose constraint, then we cropped the thyroid out of PTVs and further reduced thyroid dose. Target coverage was delivering 100% dose to ≥ 93% of PTV and 95% of dose to > 99% of PTV.

Results: Originally, average mean dose to thyroid was 5580 cGy. In model I, this dropped to 4325 cGy (p < 0.0001). In model II, average mean dose was reduced to 3154 cGy (p < 0.0001). For PTV low and PTV int, all had acceptable target coverage.

Conclusion: In patients with oral-cavity and oropharyngeal cancers, mean dose could be significantly reduced using a thyroid-optimized or thyroid-sparing IMRT technique with adequate coverage.

Keywords: Hypothyroidism; Intensity-modulated radiotherapy; Radiation toxicity; Thyroid-optimized; Thyroid-sparing.