Comparison of the Kinetics of Hematologic Recovery in Aplastic Anemia After Total Nodal Irradiation Between Helical Tomotherapy and Conventional Radiotherapy

Abstract

<h3>Purpose/Objective(s)</h3> Total nodal irradiation (TNI) followed by antithymocyte globulin (ATG) has been using as the conditioning regimen before allogeneic hematopoietic stem cell transplantation (HSCT) in aplastic, severe aplastic, and very sever aplastic anemia. As technology developed in radiotherapy, helical tomotherapy has been applied to TNI. This study compares the kinetics of hematologic changes after TNI between helical tomotherapy and 3D conformal radiotherapy (3DRT) in aplastic anemia patients. <h3>Materials/Methods</h3> Between January 2010 and December 2020, 34 patients underwent TNI before HSCT. According to different radiotherapy methods, patients were divided into two groups: 16 patients (3DRT) and 18 patients (Tomotherapy). For one month after TNI, hematologic values including absolute neutrophil counts (ANC), absolute lymphocyte counts (ALC), platelet counts, and hemoglobin counts were reviewed and analyzed. <h3>Results</h3> All but one patient achieved engraftment successfully with neutrophils (median 12 days, range 4 ∼ 19) and platelets (median 14 days, range 7 ∼ 66). Median age at TNI was 37.3 years (range, 19.4 ∼ 64.6). TNI dose was 750cGY in single fraction while two patients were treated with 700cGY. 15 patients were treated as second allogenic HSCT after graft failure. All hematologic value changes including ANC, ALC, platelet and hemoglobin didn't show significant difference between two groups (<i>P</i> = 0.185, <i>P</i> = 0.287, <i>P</i> = 0.127, and <i>P</i> = 0.244). ANC showed lowest value at nine days after TNI in both group and recovered afterwards, while ALC showed lowest value at three days after TNI. Platelet showed lowest value at nine days after TNI in 3DRT, and 12 days after in tomotherapy. Successful engraftment of ANC between two groups weren't significantly different (<i>P</i> = 0.320), though, successful engraftment of platelet between two groups showed significant difference (<i>P</i> = 0.003), <h3>Conclusion</h3> The kinetics of hematologic values after TNI using tomotherapy and 3DRT didn't show significant difference. The method of radiotherapy needs to be decided carefully, considering other factors including economic evaluation, side effects, and outcomes. It needs further studies.