Program Information
Radiation Related Lymphopenia for Lung SBRT Treatments: Measurement Versus Simulation
T McMullen1*, S Liyanage2 , C Alonso1 , K Wijesooriya1 , (1) University of Virginia, Charlottesville, VA, (2) Albemarle High School, Charlottesville, VA,
Presentations
TU-C2-GePD-JT-3 (Tuesday, August 1, 2017) 10:00 AM - 10:30 AM Room: Joint Imaging-Therapy ePoster Theater
Purpose: Severe radiation treatment related lymphopenia (TRL) is observed in sites such as brain, pancreas, and breast. It has been shown that in the case of pancreatic cancer, SBRT leads to much less lymphopenia (14%) compared to fractionated radiotherapy (72%). We quantified the TRL for lung treatments for both SBRT and normal fractionation. We also evaluated the correlation between lymphocyte reduction and RTOG 0915 and 0813 dosimetric limits for critical structures in the lung. A simulation was developed to evaluate the increase in lymphocyte reduction when the tumor is close to great vessels.
Methods: We have analyzed a set of 41 lung tumor patients who received treatment via stereotactic body radiation therapy (SBRT) between 2008 and 2016. Similar analysis was performed on a non-SBRT data set consisting 286 patients. Blood data for these patients were accessed from a Clinical Data Repository (CDR) at our institution. Simulations were done using MATLAB taking into account, the exact treatment plan, dose, structure set, and image set, taking in to account the delivery time for a 12Gy x 5 treatment, mixing of moving blood, and great vessel blood velocity differing from the rest of the body.
Results: Model confirmed that treatment of lung SBRT leads to higher lymph kill when blood rich organs such as great vessels receive significant doses, in agreement with the measured patient data. According to the model, a 12 Gyx5 lung SBRT plan would deliver 44% of the blood volume a dose of 1 Gy. The proximity of the tumor to great vessels increases this fraction to 70%.
Conclusion: During lung SBRT treatments, a high lymphocyte kill was observed when the treatment volume is close to great vessels, heart, or entrance beams pass through great vessels. Doses to moving blood determined from simulation show similar behavior to measurement.
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