Abstract
A new target autocrop function was introduced in the Varian Eclipse™ treatment planning software (version 15.5 above) (Lohynská in Klin Onkol 33(4):288-294, 2020). The study aimed to evaluate this new target autocrop impact on nasopharyngeal carcinoma (NPC) plan quality and delivery efficiency. Randomly 66 approved NPC simultaneous integrated boost (SIB) intensity-modulated radiation therapy (IMRT) treatment plans were retrospectively studied. The manual cropping-based plans served as reference and were designed using sliding-window IMRT. Reference plans were re-optimized with identical plan parameters following the institutional clinical protocol, except for the redundant optimization objective of the manual cropping targets deleted. Additionally, each target within 5mm of another had one minimum objective at 100% volume and one maximum objective at 0% volume for the autocrop plans. Plan quality was assessed based on selected parameters, including TCP (tumor control probability), NTCP (normal tissue complication probability), conformality index (CI), homogeneity index (HI), and dose-volume characteristics. Additionally, the delivery efficiency, the total plan treatment time defined as a sum of monitor units (MUs) for each treated field, and delivery accuracy, γ passing rate of treatment plan quality assurance (QA) also were compared. Both the manual cropping plans and the autocrop plans could be approved by an experienced oncologist. Overall, the autocrop plans could provide approximately a 13% reduction in linac MU while maintaining comparable plan quality, radiobiological ranking, and accuracy to the manual cropping plans. The new target autocrop tip facilitated the SIB IMRT plans for nasopharyngeal cancer patients. The autocrop could guarantee the quality and delivery accuracy of the radiotherapy plan and improved the planning efficiency, treatment efficiency, and reduced machine wear and tear. It was a promising tool for optimal plan selection for NPC SIB IMRT.
Highlights
nasopharyngeal carcinoma (NPC) is prevalent in the east and southeast Asia
A new target autocrop function was introduced in the Varian EclipseTM treatment planning software
Plan quality was assessed based on selected parameters, including tumor control probability (TCP), normal tissue complication probability (NTCP), conformality index (CI), homogeneity index (HI), and dose-volume characteristics
Summary
Treatment options include radiotherapy or chemotherapy, or a combination of both. NPC is highly sensitive to ionizing radiation, and radiotherapy is the mainstay treatment modality for non-metastatic disease. The widespread application of individualized IMRT strategy and advanced imaging-guided technique has contributed to improved survival with reduced toxicities.[1−3]. Radiotherapy techniques have been progressed from conventional two-dimensional radiotherapy (2DRT) to three-dimensional conformal radiotherapy (3DCRT) and to IMRT in the last two decades. Considered the complexity of the shape and configuration of tumor and lymph nodes in the target volume and the proximity of OARs, surgery is usually not feasible for the primary treatment of NPC. IMRT is the current preferred method[4,5] and has better clinical outcomes in treatment plans for NPC patients, such as achieving more accurate target dose distribution and better protection of normal tissues.[6−8]
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