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Background: Local recurrence is the most common pattern of failure in head and neck cancer. It can therefore be hypothesised that some of these patients would benefit from an intensified local treatment, such as radiation dose escalation of the primary tumour. This study compares treatment and toxicity outcomes from two different boost modalities in oropharyngeal cancer: simultaneous integrated boost (SIB) and brachytherapy boost., Methods: Two hundred and forty-four consecutive patients treated with > 72 Gy for oropharyngeal squamous cell carcinoma between 2011 and 2018 at our institution were retrospectively analysed. Data on side effects were collected from a local quality registry and supplemented with a review of medical records. Patients receiving a brachytherapy boost first had external beam radiotherapy consisting of 68 Gy in 2 Gy fractions to the gross tumour volume (GTV), and elective radiotherapy to the neck bilaterally. The brachytherapy boost was typically given using pulsed dose rate, 15 fractions and 0.56-0.66 Gy per fraction [total dose in EQD2 = 75.4-76.8 Gy (α/β = 10)]. The typical dose escalated radiotherapy with external beam radiotherapy only, was delivered using SIB with 74,8 Gy in 2.2 Gy fractions [EQD2 = 76.0 Gy (α/β = 10)] to the primary tumour, 68 Gy in 2 Gy fractions to GTV + 10 mm margin and elective radiotherapy to the neck bilaterally., Results: Dose escalation by SIB was given to 111 patients and brachytherapy boost to 134 patients. The most common type of cancer was base of tongue (55%), followed by tonsillar cancer (42%). The majority of patients had T3- or T4-tumours and 84% were HPV-positive. The 5-year OS was 72,4% (95% CI 66.9-78.3) and the median follow-up was 6.1 years. Comparing the two different dose escalation modalities we found no significant differences in OS or PFS and these results remained after a propensity-score matched analysis was performed. The analysis of grade ≥ 3 side effects showed no significant differences between the two different dose escalation techniques., Conclusions: We found no significant differences in survival or grade ≥ 3 side effects comparing simultaneous integrated boost and brachytherapy boost as alternative dose escalation modalities in the treatment of oropharyngeal cancer., (© 2023. The Author(s).)

Background: There is a lack of consensus concerning the definition of re-irradiation and re-irradiation volumes in head and neck cancer (HNC). The aim of the present study is to introduce a more strict definition of the re-irradiated volume that might better predict the risk of serious side-effects from treatment., Methods: Fifty-four consecutive patients re-irradiated for HNC cancer were retrospectively analysed. CT images were deformably registered and the dose distributions accumulated after conversion to EQD2. Patients with a cumulative dose of ≥100 Gy in the overlapping volume (V100) were included in the study. Survival data and radiation-related acute and late toxicities were recorded., Results: The overall survival of all included patients at 2 and 5 years was 42.6 and 27.3% respectively and the progression free survival at 2 and 5 years was 32.5 and 28.5% respectively. The overall rate of any event of severe (grade ≥ 3) acute and late toxicity was 26 and 51%, respectively. We found that severe acute toxicity was more common in patients who had a larger overlapping volume (V100 > mean) where 43% of the patients experienced grade ≥ 3 acute toxicity, compared to the patients with smaller overlapping volumes (V100 < mean) where only 11% had severe toxicity (p = 0.02). The seemingly high rates of late toxicity in the present study could be due to the use of a more strict definition of re-irradiation. In previous studies also patients with low dose overlap are included and our results imply that there is a risk that previous studies might have overestimated the risk-benefit ratio in re-irradiation of HNC., Conclusions: Our study describes the outcome of a patient material where a more strict definition of the re-irradiated volume is used. With this definition, which could better describe the volume of highest risk for serious complications, we found that larger such overlapping volumes result in an increase in severe acute side-effects. A clear definition of re-irradiation and re-irradiation volumes is of utmost importance for future studies of HNC to make results from different studies comparable.