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The objective of this study was to determine the outcomes of radical radiotherapy for early glottic squamous cell carcinoma (EGSCC) with the policy of increasing the fraction size during radiotherapy when the overall treatment time (OTT) was expected to be prolonged. Patients diagnosed with clinical T1-2N0M0 EGSCC, who were treated with radical radiotherapy between 2008 and 2019 at Hokkaido University Hospital, were included. Patients received 66 Gy in 33 fractions for T1 disease and 70 Gy in 35 fractions for T2 disease as our standard regimen (usual group [UG]). If the OTT was expected to extend for >1 week, the dose fraction size was increased from 2.0 to 2.5 Gy from the beginning or during radiotherapy (adjusted group [AG]). At this time, we performed a statistical analysis between UG and AG. In total, 116 patients were identified, and the treatment schedules of 29 patients were adjusted. The median follow-up was 60.9 months. In the T1 group, the cumulative 5-year local failure rate was 12.0% in the AG and 15.4% in the UG, and in the T2 group, the rate was 40.7% in the AG and 25.3% in the UG. There were no significant differences between the AG and UG. Similarly, no significant differences were observed for overall survival and progression-free survival rates. Our single-institutional retrospective analysis of EGSCC patients suggested that a method of adjusting the radiotherapy schedule to increase fraction size from the beginning or during the course may be effective in maintaining treatment outcomes. [ABSTRACT FROM AUTHOR]

Introduction: Sequential boost intensity‐modulated radiotherapy (SQB‐IMRT) uses two different planning CTs (pCTs) and treatment plans. SQB‐IMRT is a form of adaptive radiotherapy that allows for responses to changes in the shape of the tumour and organs at risk (OAR). On the other hand, dose accumulation with the two plans can be difficult to evaluate. The purpose of this study was to analyse patterns of loco‐regional failure using deformable image registration (DIR) in hypopharyngeal cancer patients treated with SQB‐IMRT. Methods: Between 2013 and 2019, 102 patients with hypopharyngeal cancer were treated with definitive SQB‐IMRT at our institution. Dose accumulation with the 1st and 2nd plans was performed, and the dose to the loco‐regional recurrent tumour volume was calculated using the DIR workflow. Failure was classified as follows: (i) in‐field (≥95% of the recurrent tumour volume received 95% of the prescribed dose); (ii) marginal (20–95%); or (iii) out‐of‐field (<20%). Results: After a median follow‐up period of 25 months, loco‐regional failure occurred in 34 patients. Dose–volume histogram analysis showed that all loco‐regional failures occurred in the field within 95% of the prescribed dose, with no marginal or out‐of‐field recurrences observed. Conclusion: The dosimetric analysis using DIR showed that all loco‐regional failures were within the high‐dose region. More aggressive treatment may be required for gross tumours. [ABSTRACT FROM AUTHOR]