ESTRO 2022 - Abstract Book

S745

Abstract book

ESTRO 2022

B. Bachtiary 1 , D. Veraguth 2 , N. Roos 3 , S. von Felten 4 , D. Weber 3

1 Paul Scherrer Institute , Center for Proton Therapy, Villigen, Switzerland; 2 Universital Hospital of Zurich, Department of Otorhinolaryngology-Head and Neck Surgery, Zurich, Switzerland; 3 Paul Scherrer Institute, Center for Proton Therapy, Villigen, Switzerland; 4 University of Zurich, Epidemiology, Biostatistics and Prevention, Zurich, Switzerland Purpose or Objective To analyze the toxicity of pencil beam scanning proton therapy (PBS-PT) on hearing function in patients with skull base tumors. Materials and Methods Fifty-one patients with skull base tumors treated with PBS-PT between 2003 and 2017 were analyzed regarding hearing toxicity using NCI CTCAE and pure tone average (PTA) evaluation. None of the patients received chemotherapy and all had a hearing test before the start of PBS-PT and at least one hearing test after therapy. While the CTC classification uses a threshold shift for any hearing frequency for the evaluation, PTA evaluation uses only those frequencies in decibel (dB) that are significant for speech understanding. PTA gives a snapshot of an individual’s hearing level in each ear and was calculated for every ear (n=102) as the average of the frequencies of 0.5, 1, 2 and 4 kHz and analyzed in a linear mixed-effects model. The increase in PTA indicates a hearing deterioration. Results The median age at treatment start was 50 years (range, 13-68). Forty-seven % of skull base tumors were Chordoma, 29.4 % Chondrosarcoma, 5.9 % Meningioma, and 17.7% head and neck cancers. Patients received a mean tumor dose of 71.1 Gy (RBE) (range, 52-77.8) and a mean cochlear dose of 37 Gy (RBE) (range, 0.03-72.7). After a median follow up of 11 months (2-107,), 16 patients (31%) had an unchanged hearing ability, 11 (22%) patients presented with mild hearing loss 15-25 dB (CTCAE Grade 1) and 24 patients (47%) a hearing loss >25 dB (CTCAE Grade > 2), respectively. No improved hearing ability was recorded. The analysis of the PTA for each ear before the start of PBS-PT revealed that 65 ears had a normal hearing threshold of < 20 dB (excellent-good) but in 37 ears hearing was already moderate to severe impaired (35-95 dB) and one patient even had a complete hearing loss in one ear (>95 dB). Median PTA for all ears was 15 dB (IQR 15) and increased after PBS-PT to 23.7 dB (IQR 35) indicating a hearing impairment. In 35 patients, the hearing test also included information on bone conduction allowing determining the type of hearing loss. Sensorineural (43%) or mixed (40%) hearing loss was the most common cause for hearing deterioration. In the linear mixed effect model, mean cochlear dose (p<0.01), baseline PTA (p<0.01), age (p=0.03), and time after PBS- PS (p<0.01) could be identified as significant negative factors influencing hearing function. Conclusion The majority of skull base tumor patients had hearing impairment after PBS-PT. About half of the hearing loss identified was purely sensorineural while the other half had a combination of conductive and sensorineural hearing loss. Cochlear dose, baseline PTA, age and time after treatment are significant factors for hearing loss after proton therapy. M. Massaccesi 1 , V. Fuga 1 , N. Dinapoli 1 , C. Rupe 2 , M. Olivieri 1 , F. Beghella Bartoli 1 , C. Mazzarella 1 , M. Panfili 3 , R. Calandrelli 3 , S. Settimi 4 , C. Lajolo 2 , M.A. Gambacorta 1 , F. Miccichè 1 1 Fondazione Policlinico Universitario Agostino Gemelli IRCCS, Radiation Oncology Department, Rome, Italy; 2 Fondazione Policlinico Universitario Agostino Gemelli IRCCS, Head and Neck Department, Rome, Italy; 3 Fondazione Policlinico Universitario Agostino Gemelli IRCCS, UOC Radiologia e Neuroradiologia - Polo Diagnostica per immagini, radioterapia, oncologia ed ematologia, Area diagnostica per immagini, Rome, Italy; 4 Fondazione Policlinico Universitario Agostino Gemelli IRCCS, Institute of Otolaryngology, Head and Neck Surgery, Rome, Italy Purpose or Objective In this observational study we observed the relationship between the variation of mouth opening over time and the dose to the mastication structures in patients with head and neck cancer (HNC) treated with radical radiotherapy. Materials and Methods Mouth opening of HNC patients who underwent radiotherapy (RT) +/- concurrent chemotherapy with radical intent between 2017 and 2021 was prospectively measured prior to RT (baseline) and at regular follow-up appointments at 15 and 30 days during RT and 3 and 6 months post-RT. Clinical factors (Sex, Age, Diabetes, Smoke, Stage, Anatomical site, concurrent chemotherapy, previous surgery) have been investigated with respect to the decrease of mouth opening. The Histogram Dose-Volume (DVH) of each mastication structure (mandibular condyle, choroid process, intercondylar notch, glenoid rim, masseter, temporal, lateral and medial pterygoid muscles) was extracted and data were analyzed using DVHs sum for paired structures or the only remaining structures in case of single structure (after surgery). The outcome was evaluated as the maximum decrease of mouth opening measure. Multiple linear regression models were computed, considering multiple VDoses for each DVH sum, at 0.1 Gy step. The best performing value of Vdose for each structure was selected according to the maximum value of adjusted R 2 . In multivariate analysis, the cross correlation among the selected VDose to each mastication structure was tested using the Pearson correlation test. PD-0827 Dose volume correlates of mouth opening reduction after radiotherapy for HNC: comprehensive analysis