16. Cervix cancer - The GEC-ESTRO Handbook of Brachytherapy

Cervix cancer

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THE GEC ESTRO HANDBOOK OF BRACHYTHERAPY | Part II Clinical Practice Version 1 - 01/09/2023

Figure 8. Adaptive target concepts for a stage IIB bulky cervical cancer at brachytherapy (same patient as in Fig 7) Adaptive target volumes at time of brachytherapy: CTV-T_HR based on the tumour burden after chemo-radiation i.e. the GTV-Tres and any residual pathologic tissue (stripes), and a CTV-T_IR based on the tumour burden at diagnosis i.e. the GTV-Tinit. The CTV-T_LRinit represents the compartments of potential tumor spread at diagnosis (Modified from ICRU 89)

Figure 7. Initial target concepts (EBRT/IMRT) for a stage IIB bulky cervical cancer at diagnosis Initial GTV-T and CTV-T: large GTV-T init ,, initial CTV-T HR, and initial CTV-T LR: coronal, transversal and sagittal view. (Modified from ICRU 89 and EMBRACE II protocol, www. embracestudy.dk).

Figure 9. GTV-T res at time of brachytherapy The GTV-T res is defined as residual high signal abnormality on T2-weighted MRI. Palpable induration in the parametria should not be included as this cannot be easily distinguished from radiation fibrosis.

At time of diagnosis, the following volumes are defined (Figure 7): • Initial gross tumour volume (GTV-Tinit)- the GTV-Tinit is the primary tumour at diagnosis as assessed by clinical examination and imaging. The clinical and imaging volumes may be different, and a composite GTV-T should be delineated in these situations. • Initial high-risk clinical target volume (CTV-T_HRinit) - the CTV-T_HRinit is the volume bearing the highest risk of recurrence at diagnosis. As a minimum, this includes the whole cervix in addition to the GTV-Tinit. • Initial low-risk clinical target volume (CTV-T_LRinit) – the CTV-T_LRinit represents compartments at risk for potential microscopic spread from the primary tumour. In locally advanced cervical cancer, the CTV-T_LRinit comprises the whole

parametria, the whole uterus, the upper part of the vagina, and the anterior/posterior spaces towards the bladder and rectum. For definitive radiotherapy, additional adaptive volumes are defined at the end of initial chemo-radiation with 45-50 Gy (which is assumed sufficient to control microscopic disease), i.e. at the time of BT. The relevant volumes (Figure 8) are: • Residual gross tumour volume (GTV-T res ) - residual tumour at the time of BT. • Adaptive high-risk clinical target volume (CTV-T_HR) – volume bearing the highest risk for recurrence. • Intermediate-risk clinical target volume (CTV-T_IR) – accounts for original GTV-Tinit at diagnosis