Clinical Impact of the Bolus in Intensity-Modulated Radiotherapy and Volumetric-Modulated Arc Therapy for Stage I–II Nasal Natural Killer/T-Cell Lymphoma

Abstract

<b><i>Introduction:</i></b> To estimate the clinical impact of bolus in intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT) for stage I–II nasal natural killer/T-cell lymphoma (NNKTCL), including target quality, organs at risk (OARs) sparing, and tumor control probability (TCP). <b><i>Methods:</i></b> Two different treatment plans were designed in IMRT and VMAT for 10 stage I–II NNKTCL patients. The clinical plans added bolus perfectly contacting the nose skin, similar to common clinical planning design practices. The edited bolus plans resulted from dose recalculation with the edited bolus, which simulated the actual shape of a commercial flat bolus during treatment. All the plans were with no beam passing through the couch avoiding beam attenuation caused by the couch. Differences between both types of plans in target quality, OARs sparing, and TCP were evaluated. <b><i>Results:</i></b> Compared with clinical plans, the D<sub>98%</sub>, D<sub>2%</sub>, D<sub>mean</sub>, and TCP of edited bolus plans with IMRT slightly decreased (<i>p</i> = 0.002, 0.015, 0.000, and 0.000), the homogeneity index increased 8.33% (<i>p</i> = 0.024), and the doses to a small number of OARs slightly changed. Similar results were obtained for VMAT. <b><i>Conclusion:</i></b> The bolus deformation in practical clinical treatment resulted clinically in tiny changes with respect to the target coverage, OARs sparing, and TCP in both IMRT and VMAT for stage I–II NNKTCL. This implied that the clinical impact of the bolus<b><i></i></b>can be negligible when utilizing it to increase the dose to irregularly shaped tumors in the nasal area.

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

“…where TCD 50 represents the dose to kill 50% of the tumor cells when the tumor is homogeneously irradiated and the unitless parameter r 50 describes the slope of the dose-response curve. The values of TCD 50 , r 50 , and a used to calculate the TCP in this study were 14.65, 0.41, and −13, respectively (Liu et al, 2020).…”

“…In planning IMRT or VMAT cases, the RT plan is generally designed and evaluated on the basis of physical objectives; however, the plan evaluation based on biological indicators is more relevant to the clinical efficacy (Liu et al, 2020). Utilizing DVHs data and reliable biological parameters, various radiobiological models, such as the Poisson model, the Niemierko model, and the Marsden model, have been developed to calculate the TCP and normal tissue complication probability to estimate the clinical efficacy of RT plans (Gay & Niemierko, 2007;Liu et al, 2020). However, the application of these models is limited by the inadequacy of fitting biological parameters.…”

“…Niemierko (Gay & Niemierko, 2007;Liu et al, 2020) also introduced an EUD-based TCP mathematical model, where the TCP is calculated using the following formula:…”

Dosimetric and Radiobiological Impact of Flattening Filter‐Free Beam and Dose Calculation Algorithm Using RapidArc Plans for Cervical Cancer Treatment

“…Radiotherapy plans are generally designed and evaluated based on physical objectives; however, plan evaluations based on biological indicators are more relevant to clinical efficacy. 29 OAR: organ at risk; NTCP: normal tissue complication probability; LKB: Lyman-Kutcher-Burman; LQ: linear quadratic; SD: standard deviation; FF: flattening filter; FFF: flattening filter-free; AAA: analytical anisotropic algorithm; AXB: acuros XB; AAA_F: planned using FFF beam; AXB_F: planned using FFF beam.…”

“…In the current study, dose reduction (V 30 and D 2cc ) was observed in the femoral heads with an FFF beam; however, only V 30 was significant for both computation algorithms. Radiotherapy plans are generally designed and evaluated based on physical objectives; however, plan evaluations based on biological indicators are more relevant to clinical efficacy 29 . DVH data, reliable biological parameters, and various radiobiological models such as the Poisson and LKB models have been developed to calculate the probability of normal tissue complications to estimate the clinical efficacy of radiotherapy plans.…”