ESTRO 2023 - Abstract Book

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Saturday 13 May

ESTRO 2023

in Table1. All MR-adapted plans had less than 2% variation in all targets and OAR. Differences in CTV_T_LR dose coverage were significant for 3/4 Pts (figure1). Number of fx exceeding the <2% dose variance with MR-guided plans: CTV_T_LR (Pt1= 8, Pt2 =4, Pt4 = 1). There was significant underdosing to the CTV-E with MR-guided plan for all Pts. Number of fx exceeding the <2% dose variance CTV_E MR-guided plans: (Pt1=13, Pt2 =15, Pt3=13, Pt4= 11). MR-adapted plan reduction D0.1% to bowel (2Pt), sigmoid (3Pt) and bladder (2Pt). Number of fx exceeding the <2% dose variance with MR-guided plans: bladder (Pt2=2, Pt4 =1), bowel (Pt2=5, Pt4 =3), sigmoid (Pt1= 2, Pt3 =3, Pt4=2). Overall, the number of fx which required adaptation was: {Pt1= 16\22 (72%)}, {Pt2=20\22 (83%)}, {Pt3=13\22 (59%)}, {Pt4=11\24(46%)}.

Conclusion MR-adapted improved the CTV_T_LR and CTV_E D99% coverage in 72%, 83%, 59% and 46% of total fraction for Pt 1 to 4 when compared to MR-guided. For OAR, patients benefited from a small decreased dose to the bladder, sigmoid and bowel. Number of fx exceeding the <2% dose variance with MR-guided plans was > 40% in all patients, suggesting that frequent adaptation is beneficial. This warrants extra investigation in a larger population to determine the optimal frequency of the adaptation.

Proffered Papers: Gynaecology

OC-0129 Impact of brachytherapy applicator on morbidity and local control in cervix cancer: EMBRACE study