Utilizing Online Adaptive MRI-Guided Stereotactic Body Radiotherapy for the Treatment of Pancreatic and Intra-Abdominal Cancers

The utilization of a linear accelerator in conjunction with an MRI holds significant promise for advancing MRI-guided stereotactic body radiation therapy. Previous studies predominantly relied on manufacturer-specified MRI sequences, particularly T2 Weighted, facing challenges in identifying organs at risk (OAR) and addressing pancreatic and intra-abdominal cancers. This research introduces a novel approach by harnessing the effectiveness of a T1 Weighted sequence to improve tumor and OAR visibility during online adapted-to-position (ATP) and adapted-to-shape (ATS) planning in MRI-guided radiation therapy. A cohort of 30 patients, including 20 with pancreatic cancer and 10 with intra-abdominal cancer, underwent simulations for planning before embarking on multi-fractionated treatment. The incorporation of T1 Weighted imaging significantly enhanced tumor and contouring precision, enabling swift and accurate planning during ATP and ATS. Plan quality for all 26 patients depended on the proximity of OAR to the target tumor, with gross tumor volume D90% and planned target volume D90% achieving 96 ± 5% and 92 ± 9%, respectively. The adoption of T1 Weighted imaging, with a reduced imaging time of approximately 120 seconds compared to 360 seconds for T2 Weighted imaging, not only minimized treatment margins for OAR sparing but also improved tumor visualization and reduced uncertainties in target/OAR demarcation. In the initial 20 patients, the average duration of MRI-guided radiation therapy was 55 ± 15 minutes for ATP and 79 ± 20 minutes for ATS. This study underscores the potential of MRI-guided radiation therapy in Asia, presenting an improved approach for addressing intra-abdominal and pancreatic cancer. T1 Weighted imaging emerges as a transformative tool, elevating visualization efficacy and streamlining the planning process, ultimately enhancing patient care and treatment outcomes.