Oct 01

QP 25 - Radiation and Cancer Physics 11: Advances in Dosimetry Optimization and Adaptive Planning

1148 - Early Salivary Gland Shrinkage is Associated with an Increased Risk of Acute Xerostomia in Head and Neck Cancer Patients Following Radiotherapy

10:55am - 11:00am PT

Room 160

Presenter(s)

Teeradon Treechairusame, MD - Memorial Sloan Kettering Cancer Center, New York, NY

T. Treechairusame^1,2, P. Zhang³, Y. C. Hu³, E. Aliotta³, A. Li³, M. Aristophanous³, L. I. Cervino³, J. O. Deasy³, N. Y. Lee², P. Zhang³, and J. H. Oh³; ¹Division of Radiation Oncology, Department of Radiology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand, ²Department of Radiation Oncology, Memorial Sloan Kettering Cancer Center, New York, NY, ³Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, NY

Purpose/Objective(s):

This study investigated the relationship between salivary gland shrinkage during radiotherapy and acute xerostomia in head and neck cancer (HNC) patients.

Materials/Methods:

We developed an Automated Watchdog in Adaptive Radiotherapy Environment (AWARE) program for HNC patients to monitor changes in tumor and organ-at-risk (OAR) volumes using weekly cone-beam computed tomography (CBCT) images. Gross tumor volume (GTV) and OAR contours were propagated from the planning CT to the weekly CBCTs using deformable registration. In this study, we analyzed 162 HNC patients who were treated at our institution between 2021 and 2024 and monitored using the AWARE program. The National Cancer Institute's Common Terminology Criteria for Adverse Events (CTCAE) version 5.0 was employed to grade toxicities. Acute xerostomia was defined as grade 2 or greater, occurring during or within 3 months after radiotherapy completion. We compared weekly salivary gland (parotid and submandibular) shrinkage and radiation dose between patients who developed acute xerostomia and those who did not.

Results:

Of the 162 HNC patients, 45 (27.8%) developed acute xerostomia. Weekly shrinkage rates for ipsilateral parotid gland were significantly different between patients who developed acute xerostomia and those who did not. The xerostomia group exhibited significantly greater ipsilateral parotid gland shrinkage at weeks 1, 2, 3, and 6-7 (13.2%, 18.3%, 22.7%, and 35.3%, respectively; p=0.01, p=0.004, p=0.03, and p<0.0001, t-test) compared to the no xerostomia group (7.8%, 11.2%, 17.6%, and 23.1%). The xerostomia group also demonstrated significantly greater contralateral parotid gland shrinkage at weeks 1, 2, 3, and 6-7 (13.6%, 18.3%, 24.9%, and 34.6%, respectively; p=0.02, p=0.0007, p<0.0001, and p<0.0001) compared to the no xerostomia group (8.9%, 10.0%, 15.6%, and 21.7%). In addition, the xerostomia group exhibited significantly greater submandibular gland shrinkage at week 2 (14.2%) compared to the no xerostomia group (8.6%; p=0.02). Patients who developed acute xerostomia received a significantly higher mean dose to the ipsilateral parotid gland (average mean dose: 25.5 Gy) compared to those who did not (average mean dose: 20.4 Gy; p=0.005).

Conclusion:

Greater parotid gland shrinkage (both ipsilateral and contralateral) during radiotherapy was significantly associated with an increased risk of acute xerostomia. This early signal may enable targeted adaptive radiotherapy to reduce parotid gland dose and potentially mitigate this side effect.