Inter-fraction target and OARs reproducibility in cervical cancer: Influence of immobilization systems and patient positioning verified by daily fan beam CT.

Abstract

IntroductionTo assess radiotherapy plans quality, the reproducibility of the targets and organs at risk (OARs) in cervical cancer radiotherapy with different immobilizations and positioning.MethodsSixty definitive cervical cancer patients were enrolled and immobilized with the Orfit Rack (prone), the Personalized Prone Plate (PPP) (prone), and the vacuum bag (VB) (supine), respectively. Dosimetric metrics and daily reproducibility of the targets and OARs on fan beam CT (FBCT) were analyzed.ResultsThe Orfit Rack and PPP (prone position) provided slight advantage in OARs protection. The reproducibility rates of targets were 56.64 % (Orfit Rack), 64.95 % (PPP), 77.88 % (VB), and 61.25 % (prone). The VB (supine position) showed smaller shifts in Superior-Inferior and Anterior-Posterior direction, p ConclusionsCompared to the PPP and Orfit Rack (prone position), the VB (supine position) can provide better targets and OARs reproducibility and make patient set-up more convenient during the radiotherapy treatment, yet OAR dose constraints must be considered in treatment planning to ensure safety and efficacy.Implications for practiceIt is recommended to use the VB immobilization (supine) to ensure the reproducibility of target and OARs during treatment.