Magnetic-resonance-guided Radiation Therapy With Simultaneous Integrated Boost at Mid-bladder Volume for Bladder Cancer
Abstract Background and Purpose: To report the workflow and dose accumulation for bladder preservation for a bladder cancer patient, using magnetic-resonance-guided radiation therapy (MRgRT) and the simultaneous integrated boost (SIB) technique at mid-bladder volume.Materials and Methods: A muscle-invasive bladder cancer patient was treated with MRgRT. The patient was treated with the SIB technique at mid-bladder volume, with 45 Gy to the whole bladder (CTV WB) and 55 Gy to the tumor bed (CTV boost) in 20 fractions. Daily re-optimization with an adapt-to-position (ATP) strategy was utilized for dose adjustment to encompass the bladder within anisotropic planning target volume (PTV WB and PTV boost). Results: The mean daily treatment time was 55 minutes (range, 35–73). The actual whole-bladder and tumor-bed-boost doses were 45.74 ± 5.91 and 54.1 ± 4.62 Gy, respectively. PTV WB encompassing CTV WB was 95.69% ± 5.36%. PTV boost encompassing CTV boost was 97.52% ± 6.05%. The actual rectal and bowel doses were below the reference plan doses.Conclusions: The use of MRgRT with the SIB and ATP strategy proved feasible for bladder cancer treatment. Mid-bladder volume allowed treatment with the SIB technique under MR monitoring.
