Real world interpretation of GEC-ESTRO image-guided brachytherapy recommendations for cervix cancer
Diez, P. Bourner, J. Sharp, A. Hoskin, Peter J McCormack, M.
Diez, P.
Bourner, J.
Sharp, A.
Hoskin, Peter J
McCormack, M.
Citations
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Abstract
Purpose or Objective
INTERLACE (NCT01566240) is an international phase III
multicentre trial of weekly induction chemotherapy
followed by standard chemoradiation versus standard
chemoradiation alone in patients with locally advanced
cervical cancer. As well as a trial protocol, detailed
radiotherapy guidelines were produced with a quality
assurance (QA) programme to ensure compliance at the 37
participating centres. The guidelines mandated GECESTRO
recommendations for image-guided adaptive
brachytherapy (IGABT) and prescribing to the high-risk CTV
(HRCTV). This study assesses adherence to these
recommendations.
Material and Methods
As part of the trial QA programme brachytherapy centres
were required to submit a brachytherapy dummy run (a
patient already treated at their centre) for central review
prior to trial participation. Both contouring and planning
were reviewed to assess their standard brachytherapy
technique. The following parameters have been
evaluated: use of MR and whether scanned with implant in
situ; HRCTV and intermediate-risk CTV (IRCTV) definition;
and dose conformity (HRCTV D90, HRCTV V100, and Vref).
Results
Of 34 institutions providing a brachytherapy service, 23
stated they performed IGABT, prescribing and optimising
to HRCTV D90. However, 3 of these centres did not use MR
in this process and 1 performed MR without the implant in
situ. 8 centres did not follow GEC-ESTRO HRCTV
delineation recommendations (see Figure 1). In 2 of the 11
centres defining an IRCTV this was not a direct expansion
of the HRCTV and in a further 2 the vagina was not edited
out of the expansion. The plan was assessed for dose
conformity around the HRCTV. Only 9 centres did this
adequately. Most of the uterus was included within the
prescription isodose in 14 centres and a large section of
the vagina in 7 centres, instead of conforming to the
HRCTV definition 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
recommendations in their entirety is critical to accurate
delivery of IGABT. Partial compliance may prove unsafe.
Description
Date
2020
Publisher
Collections
Keywords
Type
Meetings and Proceedings
Citation
Diez P, Bourner J, Sharp A, Hoskin PJ, McCormack M. OC-1037: Real world interpretation of GEC-ESTRO image-guided brachytherapy recommendations for cervix cancer. Radiotherapy and Oncology . 2020 Nov;152:S1091–2.