Image guidance and interfractional anatomical variation in paediatric abdominal radiotherapy

Abstract

Objectives: To identify variables predicting inter fractional anatomical variationsmeasured with cone-beam CT (CBCT) throughout abdominal paediatric radiotherapy, and to assess the potential of surface-guided radiotherapy (SGRT) to monitor these changes. Methods: Metrics of variation in gastrointestinal (GI) gas volume andseparation of the body contour and abdominal wallwere calculated from 21 planning CTs and 77 weekly CBCTs for 21 abdominal neuroblastoma patients (median 4y, range: 2 –19y). Age, sex, feeding tubes, and general anaesthesia (GA) were explored as predictive variables for anatomical variation. Furthermore,GI gas variationwas correlated with changes in body and abdominal wall separation, as well as simulated SGRT metrics of translational and rotationalcorrections between CT/CBCT. Results: GI gas volumes varied 74 ± 54 ml across all scans, while body and abdominal wall separationvaried 2.0 ± 0.7 mm and4.1±1.5mmfrom planning, respectively. Patients < 3.5y (p = 0.04) and treated under GA (p < 0.01) experienced greater GI gas variation; GA was the strongest predictor in multivariate analysis (p < 0.01). Absence of feeding tubes was linked to greater body contour variation (p = 0.03). GI gas variation correlated with body (R = 0.53) and abdominal wall (R = 0.63) changes. The strongest correlations with SGRT metrics were found for anteroposterior translation (R = 0.65) androtation of the left-right axis (R = −0.36). Conclusions: Young age, GA, and absence of feeding tubes were linked to stronger inter fractional anatomical variation and are likely indicative of patients benefiting from adaptive/robust planning pathways.Our data suggests a role for SGRT toinformthe need for CBCT at each treatment fractionin this patient group. Advances in knowledge: This is the first study to suggest the potential role of SGRT for the management of internal inter fractional anatomical variation in paediatric abdominal radiotherapy.

Surface guided radiotherapy practice in paediatric oncology: a survey on behalf of the SIOPE Radiation Oncology Working Group

“…However, a recent study showed that SGRT may also be able to detect gastrointestinal variations triggering adaptive RT pathways. 21 For deep-seated target volumes, especially those moving independently of bony anatomy, other imaging techniques using CBCT or MRI are generally more accurate for localization. 6 However, SGRT can reduce target localization uncertainty due to intrafraction motion by the real-time monitoring of the patient surface.…”

“…Taylor et al investigated the potential role of SGRT for the management of interfractional gastrointestinal gas volume variation in paediatric abdominal RT. 21 The key idea is that while SGRT would not replace cone beam CT (CBCT) imaging, it could enable a fully personalized Image Guided Radiotherapy (IGRT) schedule for each patient and reduce CBCT imaging to only required fractions. Also, SGRT systems have been recommended as a safety feature in paediatric treatments to assist in patient set-up and provide additional error detection.…”