Dosimetric Results for Organs at Risk From Radiation Therapy Dose De-Escalation to the Subclinical Region in Human...

The impact of radiation therapy (RT) dose de-escalation on organs at risk (OARs) for human papillomavirus-associated oropharyngeal cancer (OPC) is not known. This study retrospectively assessed OAR dosimetric outcomes of de-escalated RT for OPC.

We conducted a retrospective analysis of dosimetric data for patients with T1 to 4, N0 to 3 human papillomavirus-associated OPC treated with intensity modulated RT at a single academic institution between August, 2014 and January, 2023. All patients received 70 Gy to gross disease. The low-dose group received 30 Gy to the subclinical neck, and high-dose patients received 50-60 Gy. Propensity score matching was performed to balance differences in clinical staging between groups. Mean OAR doses were collected and compared between the groups.

A total of 575 patients were included. Of these, 226 (39.3%) had bilateral nodal disease. Significant reductions in mean doses were observed across all OARs. For matched 30 Gy patients with unilateral nodal disease, the contralateral parotid gland mean dose was 833 cGy, compared with 1391 cGy (P< .001). Other mean dose reductions included ipsilateral parotid gland (1984 vs 2769 cGy; P< .001), ipsilateral submandibular gland (5709 vs 6036 cGy; P= .008), contralateral submandibular gland (2832 vs 3734 cGy; P< .001), and larynx (2119 vs 3186 cGy; P< .001). Patients with bilateral nodal disease also had lower OAR doses in the 30 Gy group, including right parotid (1661 vs 2402 cGy; P< .001), left parotid (1725 vs 2443 cGy; P< .001), right submandibular gland (5385 vs. 6001; P= .002), left submandibular gland (5283 vs 5948 cGy; P= .005), and larynx (2341 vs 3846 cGy; P< .001).

Subclinical neck RT dose de-escalation can generate low OAR doses well under established dose constraints. These reductions have the potential to mitigate toxicities such as xerostomia and dysphagia, and they may improve long-term patient quality of life. Ongoing prospective research evaluating toxicities and quality of life from RT de-escalation for OPC is warranted.