A Dosimetric Comparison of Treatment Techniques for Stereotactic Body Radiotherapy for Pancreatic Patients

Stereotactic body radiotherapy (SBRT) is utilized in radiation therapy to deliver ablative radiation doses to tumor volumes while achieving high conformity and minimal dose to surrounding critical structures. This treatment technique allows for faster dose fall-off which allows tighter treatment margins. SBRT for pancreatic cancer has been investigated for its efficacy and has proven to be an effective treatment choice for neoadjuvant radiation therapy. Since pancreatic cancer is extremely aggressive with a high mortality rate, it is important to have a treatment option that can reduce cost and increase convenience for the patient while simultaneously providing a conformal treatment plan. SBRT is defined as a radiation therapy treatment with higher dose per fraction when compared to conventional fractionation that is completed in 5 or fewer fractions. Since these treatments are at a higher dose with less 7. This study compared the proper treatment techniques for using SBRT for pancreatic patients utilizing different energies and coplanar vs. noncoplanar beam arrangements to achieve the highest conformity and lowest doses to OARs. A total of 30 plans were created using Eclipse treatment planning system (TPS) with Anisotropic Analytical Algorithm (AAA) calculation algorithm version 16.1.0. In this study, 5 patients were used, each having 6 treatment plans created with 6X, 10X, and 6FFF energies with each energy having a coplanar beam arrangement plan along with a planned noncoplanar beam arrangement. The plans were created with consistent treatment parameters for each patient. The prescription used was recommended by the task group of the Alliance A021501 trial. Each plan was evaluated by measuring Paddick Conformity Index (PCI) and Conformity Index of the 50% isodose line (CI50%) along with organs at risk (OARs) doses such as the maximum dose of the spinal cord and cauda equina and mean doses of the kidneys, stomach, liver, small bowel, and large bowel. The energy had slight effects on the OAR doses but was not found to be statistically significant. However, the noncoplanar beam arrangement was shown to be more conformal for midrange doses as measures by the CI50%. The noncoplanar beam arrangement for SBRT pancreatic cancer treatment could be proven to improve conformity and should be considered when planning these treatments.