Investigation of Interfraction Variance of a SAVI6-1 Mini APBI Applicator in Patients with Reduced Chest Wall and Skin Sparing

Abstract

 Routine pre-treatment CT scan checks are unlikely to point out hard-to-quantify local anatomy inter-fraction variances, which are identified as the main impact factor for APBI treatments in patients with reduced chest wall and skin sparing that leads to considerable PTV-to-PTV_EVAL volume reduction (if VR = 1 – [PTV_EVALVolume/PTVVolume] proposed action value for VR = 0.30) Meticulous pre-treatment QA procedures are mandatory for the correct delivery of a SAVI6-1 mini APBI treatment and for the achievement of a high degree of conformance between the Initial reference TPS plan and the clinically delivered plan. Inter-fractional TPS plan re-evaluations should become a routine when dealing with difficult cases where the applicator is proximal to organs of risk and where highly asymmetrical PTV_EVAL volumes are employed, in order to avoid overlooking prohibitive sensitive structure doses and unacceptable PTV_EVAL coverage cutbacks. To evaluate the effect on target coverage and organ of risk sparing caused by inter-fraction variance of a SAVI6-1 mini APBI applicator in patients with small breast tissue volumes and limited skin/chest wall spacing. PURPOSE