Main Session
Sep 29
PQA 07 - Head and Neck Cancer, Lung Cancer/Thoracic Malignancies, and Nursing and Supportive Care

3450 - De-Intensified vs. Standard-Dose Proton Beam Therapy for Favorable Prognosis HPV-Mediated Oropharynx Cancer

03:45pm - 05:00pm ET
Poster Hall - Exhibit Hall A
Screen: 12
POSTER

Presenter(s)

Roi Dagan, MD, MS Headshot
Roi Dagan, MD, MS - University of Florida Proton Therapy Institute, Jacksonville, Florida

R. Dagan1,2, A. C. Casper3, C. M. Bryant1,2, and W. M. Mendenhall1,2; 1University of Florida Health Proton Therapy Institute, Jacksonville, FL, 2Department of Radiation Oncology, University of Florida College of Medicine, Jacksonville, FL, 3Department of Radiation Oncology, University of Florida College of Medicine, Gainesville, FL

Purpose/Objective(s):

Proton beam therapy (PBT) and de-intensified (DI) radiotherapy have been shown to be safe and effective in well-selected patient with favorable prognosis HPV-mediated oropharynx cancer (HPV-OPC). The purpose of this study is to compare the rates of disease control and toxicity between DI and non-DI patients treated with PBT.

Materials/Methods:

We performed a retrospective review of consecutively treated patients who received PBT (with or without chemotherapy) for favorable prognosis HPV-OPC at a single institution. Subjects met the following inclusion criteria: HPV positive (by p16 IHC or high-risk HPV ISH), non-T4, non-N3, no active smoking at time of diagnosis, and a minimum potential follow-up of 6 months. All DI patients received a =64 GyRBE (median 60 GyRBE) at 2 GyRBE/fraction. DI dose regimens included 50 cGyRBE (n = 10), 60 GyRBE (n=47), and 62-64 GyRBE (n=4). Nearly all (>90%) of DI patients were treated on prospective clinical trials (NCT03077243, NCT05268614). Non-DI patient received >65 GyRBE (median 70 GyRBE). Pencil-beam scanning (PBS) intensity-modulated PBT was used in 88% with the remaining treated with either double-scattered (DS) PBT only or a combination of DS and PBS PBT. The Kaplan Meier method was used to estimate the rates of disease control and toxicity was scored using the CTCAE version 5.

Results:

Between 8/2014 - 6/2025, 128 patients met the inclusion criteria (61 DI and 67 non-DI). The groups had similar rates of chemotherapy (80% versus 75%), cT3 (16% and 18%) with less cN2 (13% versus 27%) and accelerated fractionation (0% versus 30%) in the DI group. There was no difference between the 5y rates of disease control and survival between the DI and non-DI groups with higher rates of toxicity (CTCAEv5 grade 3 dysphagia, weight loss, or feeding-tube use and ORN) observed in non-DI patients (see table).

Conclusion:

DI-PBT results in comparable rates of disease control and survival with lower rates of toxicity compared with non-DI PBT.

 5y LRC

(95% CI)

 5y DFS

(95% CI)

 5y OS

(95% CI)

 Any Gr3 Dysphagia, Weight loss, or feeding tube use

Any ORN
DI

 95% (87-99%)

 87% (76-95%)

 87% (71-96%)

 13%

 0%
Non-DI

 97% (90-99%)

 88% (78-95%)

 92% (83-98%)

 31%

 6%
p =

 NS

 NS

 NS

 < 0.05

 < 0.05