Abstract
PurposeTo evaluate the dosimetric outcomes of a simple planning technique for improving intensity-modulated radiotherapy (IMRT) for nasopharyngeal cancer (NPC).MethodsFor 39 NPC cases, generally acceptable original plans were generated and were improved by the two planning techniques, respectively: (1) a basal-dose-compensation (BDC) technique, in which the treatment plans were re-optimized based on the original plans; (2) a local-dose-control (LDC) technique, in which the original plans were re-optimized with constraints for hot and cold spots. The BDC, original, and LDC plans were then compared regarding homogeneity index (HI) and conformity index (CI) of planning target volumes (PTVs), organ-at-risk (OAR) sparing and monitor units (MUs) per fraction. The whole planning times were also compared between the BDC and LDC plans.ResultsThe BDC plans had superior HIs / CIs, by 13-24% / 3-243%, respectively, over the original plans. Compared to the LDC plans, the BDC plans provided better HIs only for PTVnx (the PTV of nasopharyngeal primary tumor) by 11% and better CIs for all PTVs by 2-134%. The BDC technique spared most OARs, by 1-9%. The average MUs of the BDC, original, and LDC plans were 2149, 2068 and 2179, respectively. The average whole planning times were 48 and 69 minutes for the BDC and LDC plans, respectively.ConclusionsFor the IMRT of nasopharyngeal cancer, the BDC planning technique can improve target dose homogeneity, conformity and OAR sparing, with better planning efficiency.
Highlights
Nasopharyngeal cancer (NPC) is a common malignant head and neck tumor in southern China and Southeast Asia [1,2]
Because this was not a treatment-based study, our institutional review board waived the need for written informed consent from the participants
NPC is one of the cancers of which intensity-modulated radiotherapy (IMRT) plays an important role in the treatment [16,17]
Summary
Nasopharyngeal cancer (NPC) is a common malignant head and neck tumor in southern China and Southeast Asia [1,2]. Intensity-modulated radiotherapy (IMRT) has become the mainstay in the treatment of non-metastatic NPC [3]. IMRT combines several intensity-modulated beams to obtain improved dose homogeneity and highly conformal dose distributions, as well as improved normal-structure sparing. IMRT planning for NPC is challenging due to the complex anatomy, with bones, soft tissues and air cavities all in need of consideration. Organs at risk (OARs), such as spinal cord, brainstem, and parotid glands, are typically located proximately to the target volumes. The targets are prescribed at different dose levels [4] and the target volumes often have irregular concave shapes [5]
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