Online adaptive radiotherapy of urinary bladder cancer with full re-optimization to the anatomy of the day: Initial experience and dosimetric benefits

• Published in: Radiotherapy and oncology Vol. 171; pp. 37 - 42
• Main Authors: Åström, Lina M., Behrens, Claus P., Calmels, Lucie, Sjöström, David, Geertsen, Poul, Mouritsen, Lene Sonne, Serup-Hansen, Eva, Lindberg, Henriette, Sibolt, Patrik
• Format: Journal Article
• Language: English
• Published: Ireland Elsevier B.V 01.06.2022
• Subjects: Artificial intelligence; Bladder cancer; Cone-beam CT; Image-guided Radiotherapy; Online adaptive radiotherapy; Re-optimization; Online adaptive radiotherapy; oART; Cone-beam CT; Bladder cancer; Artificial intelligence; Re-optimization; Image-guided Radiotherapy
• ISSN: 0167-8140; 1879-0887
• DOI: 10.1016/j.radonc.2022.03.014

•CBCT-guided oART was feasible for patients with bladder cancer.•A novel solution with AI fostered a time-efficient oART procedure.•oART with patient-specific margins enabled large PTV-T reductions.•Conducting oART reduced critical dose-volume parameters of bowel bag and rectum. Online adaptive radiotherapy (oART) potentially reduces the dose to organs at risk (OARs) as the planning target volume (PTV) margins are reduced compared to a non-adaptive approach (non-ART). This study evaluates the feasibility and dosimetric impact of cone-beam computed tomography (CBCT)-guided oART of urinary bladder cancer for the first patients treated, using patient-specific margins. Sixteen consecutive patients with muscle-invasive bladder cancer received two or more (median = 23) fractions as oART, and remaining fractions as non-ART. The non-ART fractions were delivered with standard population-based margins, while reduced patient-specific margins based on intra-fractional variations extracted from 2-4 fractions were applied to the primary PTV (PTV-T) during the oART fractions. Target volume and coverage, and dose to OARs were compared between non-ART and oART plans, and the oART procedure time was recorded. In total, 297/512 fractions were delivered as oART with full re-optimization to the anatomy of the day. The median (interquartile range, IQR) oART procedure time, measured from the end of CBCT generation to completion of plan review, and quality assurance was 13.9 (11.9;16.6) min. The median (IQR) volume reduction in PTV-T volume was 33.9 (24.2;45.0)%, comparing oART and non-ART plans, resulting in median (IQR) reductions in bowel bag V45Gy of 18.8 (12.7;27.9)% and rectum V50Gy of 70.7 (35.9;94.8)%. By re-optimizing the plan to the daily anatomy, full target coverage was achieved at all oART fractions. oART resulted in large reductions in treatment volumes and doses to OARs, compared to non-ART, while ensuring target coverage. This indicates potential reductions in gastrointestinal toxicity.