ESTRO 2022

Session Item

Monday

May 09

10:30 - 11:30

Poster Station 2

20: Head and neck

Chair: Annett Linge, Germany

Session Type: Poster Discussion

Track: Clinical

Journey:

Hearing in cancer patients with skull base tumors undergoing pencil beam scanning proton therapy

Barbara Bachtiary, Switzerland

Presentation Number: PD-0826

Abstract

Abstract Title:

Hearing in cancer patients with skull base tumors undergoing pencil beam scanning proton therapy

Authors:

Barbara Bachtiary¹, Dorothe Veraguth², Nicolaas Roos³, Stefanie von Felten⁴, Damien Weber³

¹Paul Scherrer Institute , Center for Proton Therapy, Villigen, Switzerland; ²Universital Hospital of Zurich, Department of Otorhinolaryngology-Head and Neck Surgery, Zurich, Switzerland; ³Paul Scherrer Institute, Center for Proton Therapy, Villigen, Switzerland; ⁴University of Zurich, Epidemiology, Biostatistics and Prevention, Zurich, Switzerland

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Purpose or Objective

To analyze the toxicity of pencil beam scanning proton therapy (PBS-PT) on hearing function in patients with skull base tumors.

Material 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.