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Mapping Local Failure Following Bladder Radiotherapy According to Dose.
H Abdel-Aty1, K Warren-Oseni2, S Bagherzadeh-Akbari2
1Division of Radiotherapy and Imaging, The Institute of Cancer Research, London, UK; Department of Radiotherapy, The Royal Marsden NHS Foundation Trust, London, UK.
Clinical Oncology (Royal College of Radiologists (Great Britain))
|June 12, 2022
Summary
Local relapse after muscle-invasive bladder cancer radiotherapy often occurs within the high-dose area. This suggests biological factors may drive failure, cautioning against margin reduction in future treatment protocols.
Area of Science:
- Oncology
- Radiation Oncology
- Medical Physics
Background:
- Muscle-invasive bladder cancer (MIBC) requires effective radiotherapy.
- Understanding local relapse patterns is crucial for treatment optimization.
Purpose of the Study:
- To investigate the relationship between radiation dose and local relapse in MIBC patients treated with intensity-modulated radiotherapy.
- To analyze the spatial and dosimetric characteristics of local tumor relapse.
Main Methods:
- Phase II study of intensity-modulated radiotherapy for MIBC.
- Dose reconstruction of relapse gross tumor volume (GTV_relapse) using deformable image registration (DIR) and rigid image registration (RIR).
- Classification of failure types based on spatial and dosimetric criteria.
Main Results:
- 47% of patients experienced local relapse within the bladder.
- Deformable image registration (DIR) indicated median GTV_relapse D98% and D95% at 97% and 98% of prescribed dose.
- 65% of relapses were central high-dose failures (Type A), and 35% were peripheral high-dose failures (Type B).
- No elective dose failures (Types C, D, E) were observed.
Conclusions:
- Local relapse after MIBC radiotherapy occurs near the original tumor and within the high-dose region.
- Findings suggest potential biological drivers for treatment failure.
- Caution is advised regarding margin reduction in future radiotherapy protocols for MIBC.
