Target splitting non-coplanar RapidArc radiation therapy for a diffuse sebaceous carcinoma of the scalp: a novel delivery technique (Radiation Oncology)

Background and purpose: To compare conventional lateral photon-electron, fixed-beam intensity modulated radiation therapy (IMRT), coplanar and non-coplanar RapidArc for the treatment of a diffuse sebaceous gland carcinoma of the scalp. Methods: Comprehensive dosimetry comparisons were performed among 3D-CRT, IMRT and various RapidArc plans. Target coverage, conformity index (CI), homogeneity index (HI) and doses to organs at risk (OAR) were calculated. Monitor unites (MUs) and delivery time of each treatment were also recorded to evaluate the execution efficiency. The influence of target splitting technique and non-coplanar planning on plan quality was discussed. Results: IMRT was superior to 3D-CRT concerning targets` coverage at the sacrifice of larger irradiated brain volumes to low doses. CIs and HIs were better in coplanar RapidArc and non-coplanar RapidArc plans than 3D-CRT and IMRT. Best dose coverage and sparing of OARs were achieved in non-coplanar plans using target splitting technique. Treatment delivery time was longest in the IMRT plan and shortest in the coplanar RapidArc plan without target splitting. The 3%/3 mm gamma test pass rates were above 95% for all the plans. Conclusions: Target splitting technique and non-coplanar arcs are recommended for total scalp irradiation.