<p>Estimation of radiotherapy modalities for patients with stage I-II nasal natural killer T-Cell lymphoma</p>

Abstract

Purpose The objective of this study is to estimate radiotherapy (RT) modalities for patients with stage I-II nasal natural killer T-Cell lymphoma (NNKTCL), including plan quality, radiation delivery efficiency, cost of RT and excess absolute risk (EAR). Materials and methods Twenty-four representative patients with stage I-II NNKTCL treated with fix-field intensity-modulated radiotherapy (FF-IMRT) were re-planned for volumetric modulated arc therapy (VMAT), TomoDirect (TD) and TomoHelical (TH) on the TomoHDA system, respectively. Plan characteristics, cost of RT and EAR were compared. Results Compared with IMRT, TD and TH showed significant improvement in terms of D 98% , D 2% , cold spot volume and homogeneity index (HI) of planning target volume (PTV), while achieving worse D mean and conformity index (CI). The mean dose of oropharynx, thyroid and left salivary, and the maximum dose of right salivary by TD (249.20%, p =0.000; 52.94%, p =0.000; 160.23%, p =0.022; 122.67%, p =0.027), VMAT (15.76%, p =0.000; 23.53%, p =0.000; 34.09%, p =0.000; 31.33%, p =0.000) and TH (250.32%, p =0.000; 58.82%, p =0.000; 120.45%, p =0.020; 117.33%, p =0.032) increased significantly compared to IMRT. VMAT reduced treatment time ( p =0.000; 0.000; 0.000) and monitor units (MUs) ( p =0.000; 0.000; 0.000) obviously compared with IMRT, TD and TH. The cost of RT for TD and TH increased 150% compared with IMRT and VMAT. IMRT obtained the lowest EAR to oropharynx, thyroid, left and right salivary gland in the four treatment modalities. Conclusion The results show that both TD and TH can achieve higher conformal target quality while getting worse organs at risk (OARs) sparing and EAR to some organs than IMRT for patients with stage I-II NNKTCL. IMRT delivers the lowest dose to most OARs, VMAT requires the lower cost of RT and shortest delivery time, and TH obtained the optimal target coverage. The results could provide direction for selecting proper RT modalities for different cases.

Dosimetric Comparison of IMRT, Hybrid IMRT and Hybrid VMAT For Early Stage Right-Sided Breast Cancer

“…Recently, Schneider proposed a calculation model, namely, the EAR model, which can be adopted for SCR calculation and evaluation utilizing DVH data from the RT plan and related radiobiological parameters [16,19]. The EAR model has proved its feasibility to assess the SCR for patients with nasal natural killer T-cell lymphoma and breast cancer [19,22]. Fogliata et al [22] applied the EAR model to compare the SCR among 3D-CRT, VMAT_full, and VMAT_tang for breast cancer.…”

“…The SCR caused by RT of normal tissues can be assessed by Model excess absolute risk (EAR), as proposed by Schneider [16,17]. The Equation (1) shown below can be utilized to calculate the SCR of an organ [18,19]:…”

Clinical impact of the flattening filter free irradiation in fixed-field IMRT and VMAT for stage I–II nasal natural killer/T-cell lymphoma

“…Delineation of the target volumes and adjacent OARs was performed on the Eclipse treatment planning system (TPS,Version 13.6,Varian Medical Systems,Inc.). The delineation principles of the gross tumor volume and the clinical target volume (CTV) were described in our previous studies (Liu et al, 2019(Liu et al, , 2017. The planning target volume (PTV) was obtained by expanding the CTV 3 mm uniformly in all dimensions to offset the influence of setup errors.…”

“…A bolus with a thickness of 0.5 mm was added to all the fields of the 96 plans for dose optimization and calculation. The boundaries of the bolus were described in previous studies (Liu et al, 2019(Liu et al, , 2017.…”

“…All the IMRT FF plans contained eight coplanar fields, with gantry angles of 255°, 290°, 325°, 0°, 0°, 35°, 70°, and 105°, and the rotation angles of the collimator and the couch for all the fields were set to 0°. To maximize protection of the lenses and eyes, the position of the jaw in the two fields with gantry angles of 0° was adjusted and fixed before dose optimization, as described previously (Liu et al, 2019). Dynamic slidingwindow IMRT delivery, a flattened beam, and a fixed dose rate (DR) of 300 monitor units (MUs)/min were adopted to deliver radiation.…”