Author: Tianyuan Dai, Xiaoying Fan, Shuting Wang, Yong Yin 👨🔬
Affiliation: Department of Graduate, Shandong First Medical University, Shandong Academy of Medical Sciences, Department of Radiation Oncology Physics and Technology, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences 🌍
Purpose: Decreased lymphocytes increase the risk of infections and other problems. Radiation exposure can cause the development of severe lymphopenia. In this study, we used a dynamic blood flow model to simulate the irradiation process to obtain the circulating blood dose under proton therapy, to determine the relationship between the occurrence of SRIL and blood dose, and to establish a normal tissue complication probability (NTCP) model.
Methods: We retrospectively analyzed data from 39 lung cancer patients, recording their absolute lymphocyte counts before, during, and after treatment. SRIL was diagnosed when an event occurred during the course of treatment with an absolute lymphocyte count (ALC) < 500 µL. The histogram of circulating blood dose was simulated using a time-dependent calculation framework called hematological dose. Statistical analysis was performed using SPSS 27 software. NTCP modeling in response to blood dose was performed using the Lyman-Kutcher-Burman model of generalized equivalent dose.
Results: Patients developed varying degrees of lymphopenia during treatment. There were no statistically significant differences between the groups with/without SRIL in terms of gender, age, fractionated prescription dose, pretreatment ALC level, tumor stage, chemotherapy regimen, or treatment modality. Patients' mean ALC decreased consistently during treatment (rate, -0.047 per day). The median mean blood dose for all patients was 2.842 Gy (RBE) (range, 1.408-3.720 Gy (RBE)). Patients experiencing SRIL received significantly higher mean blood doses (p<0.006). The Dn% for SRIL had correlations. Of these, D80% had the strongest correlation with SRIL (UVA, ratio = 4.982, p < .011). NTCP modeling of lymphopenia after lung irradiation using circulating blood doses.
Conclusion: Circulating blood dose is associated with ALC depletion in radiation therapy. The NTCP model established in this study regarding SRIL provides a reference for optimizing the radiation dose for subsequent treatment planning, which is beneficial for the maintenance of the patient's immune system.