ESTRO 2024 - Abstract Book

S1198

Clinical - Head & neck

ESTRO 2024

Material/Methods:

This is a retrospective cohort study. Eligible patients had a diagnosis of SCCUP and unilateral neck disease, and were treated with radiotherapy to the INO. Patient demographics, treatment details, length of follow up and survival outcomes were collected. Survival probability was evaluated from date of diagnosis to date of death from any cause (Overall Survival/OS), death from cancer (Cancer Specific Survival/CSS) and recurrence of disease (Recurrence Free Survival/RFS), and calculated via Kaplan-Meier method. Details regarding recurrence (local; primary site emergence, regional: cervical lymph nodes or metastatic) were recorded. Potential primary sites (tonsil, base of tongue and entire oropharynx to include both these structures plus soft palate and posterior pharyngeal wall (split into ipsilateral only and bilateral oropharynx)) for each patient were retrospectively contoured and the patients’ original treatment plan was re -run to allow for evaluation of the incidental dose to these volumes. Twenty patients treated with volumetric modulated arc therapy (VMAT) between 1st August 2012 and 30th April 2016 were eligible for analysis. Median duration of follow up was 86 months (IQR 30 - 101 months). Median age was 61 years. 80% of patients had a smoking history. 65% of patients had N2b (AJCC 7th edition) disease. Tumour p16 status was not assessed in 70% of patients as the time period pre-dated routine testing, in those tested 50% had p16 positive disease. 5 year OS was 60% (CI: 42% to 86%), with 5 year CSS of 94% (CI: 84% to 100%). 5 year RFS was 78% (CI: 62% to 100%), with recurrences driven by distal metastases. Only one patient had an ipsilateral regional recurrence in the neck (in the high dose volume) but synchronous distal metastases. The remaining patients (3) with recurrence experienced distal recurrence only. There was no primary site emergence in any patient. Results:

Incidental dose to oropharynx structures (oropharynx, tonsil, base of tongue) are as shown in table 1. Figure 1 depicts the areas receiving 40-50Gy BED.

Oropharynx (Bilateral)

Oropharynx (Unilateral)

Base of Tongue (BOT)

Tonsil

Parameters

Mean Dose (Gy)

40.4 ± 5.6 20.0 ± 6.2

48.7 ± 9.0

46.4 ± 10.4

55.4 ± 12.2 42.1 ± 17.2

D95% (Gy)

42.7 ± 10.6

32.3 ± 9.1

Table 1: Dosimetry data for oropharynx structures