Abstract
Background and PurposeLiterature is non-conclusive regarding selection of beam configurations in radiotherapy for mediastinal lymphoma (ML) radiotherapy, and published studies are based on manual planning with its inherent limitations. In this study, coplanar and non-coplanar beam configurations were systematically compared, using a large number of automatically generated plans.Material and MethodsAn autoplanning workflow, including beam configuration optimization, was configured for young female ML patients. For each of 25 patients, 24 plans with different beam configurations were generated with autoplanning: 11 coplanar CP_x plans and 11 non-coplanar NCP_x plans with x = 5 to 15 IMRT beams with computer-optimized, patient-specific configurations, and the coplanar VMAT and non-coplanar Butterfly VMAT (B-VMAT) beam angle class solutions (600 plans in total).ResultsAutoplans compared favorably with manually generated, clinically delivered plans, ensuring that beam configuration comparisons were performed with high quality plans. There was no beam configuration approach that was best for all patients and all plan parameters. Overall there was a clear tendency towards higher plan quality with non-coplanar configurations (NCP_x≥12 and B-VMAT). NCP_x≥12 produced highly conformal plans with on average reduced high doses in lungs and patient and also a reduced heart Dmean, while B-VMAT resulted in reduced low-dose spread in lungs and left breast.ConclusionsNon-coplanar beam configurations were favorable for young female mediastinal lymphoma patients, with patient-specific and plan-parameter-dependent dosimetric advantages of NCP_x≥12 and B-VMAT. Individualization of beam configuration approach, considering also the faster delivery of B-VMAT vs. NCP_x≥12, can importantly improve the treatments.
Highlights
Patients treated with a combination of multi-agent chemotherapy and radiation for Hodgkin or non-Hodgkin lymphoma are mostly young at diagnosis
The study was based on a database with contoured planning CTscans and manually generated, clinically delivered plans (CLIN) of 26 previously treated female mediastinal lymphoma (ML) patients (21 Hodgkin lymphoma and 4 B cell non-Hodgkin lymphoma)
Prior to the comparisons of beam angle configurations, several analyses were performed to ensure that the autoplans used for these comparisons were clinically acceptable and of high quality
Summary
Patients treated with a combination of multi-agent chemotherapy and radiation for Hodgkin or non-Hodgkin lymphoma are mostly young at diagnosis. Radiotherapy (RT) for lymphoma has evolved by considerably decreasing target volumes (from extended field to involved field to involved site or involved node) and radiation doses (from 40 to 30 Gy or even 20 Gy in selected cases) These factors contribute to a decrease in the risk of late toxicity [1, 6, 13,14,15,16]. Applied radiotherapy techniques have evolved, with intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) emerging as alternatives to 3D conformal RT (3D-CRT) In this context, the typical low-dose bath of VMAT plans has been pointed at as a cause of concern, as it could increase the risk of secondary cancers relative to 3D-CRT [17]. Coplanar and non-coplanar beam configurations were systematically compared, using a large number of automatically generated plans
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