Isodose surface volumes in cervix cancer brachytherapy: Change of practice from standard (Point A) to individualized image guided adaptive (EMBRACE I) brachytherapy.
To investigate the isodose surface volumes (ISVs) for 85, 75 and 60 Gy EQD2 for locally advanced cervix cancer patients.
MATERIALS AND METHODS
1201 patients accrued in the EMBRACE I study were analysed. External beam radiotherapy (EBRT) with concomitant chemotherapy was followed by MR based image-guided adaptive brachytherapy (MR-IGABT). ISVs were calculated using a predictive model based on Total Reference Air Kerma and compared to Point A-standard loading systems. Influence of fractionation schemes and dose rates was evaluated through comparison of ISVs for α/β 10 Gy and 3 Gy.
MR-IGABT and individualized dose prescription during EMBRACE I resulted in improved target dose coverage and decreased ISVs compared to standard plans used with classical Point A based brachytherapy. The ISVs depended strongly on CTVHRvolume which demonstrates that dose adaptation was performed per individual tumour size and response during EBRT.