ESTRO 2020 Abstract Book

S1092 ESTRO 2020

recommendations in their entirety is critical to accurate delivery of IGABT. Partial compliance may prove unsafe.

Conclusion Moving from a 2D procedure or a standard plan in 3D to IGABT can be a steep learning curve, in particular in defining the target. Use of MRI with the implant in situ, and its careful assessment in all 3 imaging planes, is fundamental for accurate target delineation. Approximately a third of centres under-contoured the HRCTV, therefore increasing the risk of local recurrence. 11 centres over-contoured the target, having the potential to either increase the risk of toxicity or, having to reduce the prescription to remain within OAR tolerance, compromising the chance of tumour control. The same is the case where the prescription dose does not conform to the HRCTV. Only 5 centres adhered to all aspects of the GEC-ESTRO cervical IGABT recommendations that were evaluated. Although feedback was provided to all centres within INTERLACE, ongoing education may be necessary. Prospective central review was therefore carried out on the first 2 patients at each centre, with further cases assessed where required. Adoption of GEC-ESTRO