16 Cervix Carcinoma

308 Cervix Cancer

Fig 14.3: Stage IIB Cervix Cancer 41x 61 mm (pretreatment MRI (A)) and 4 cm by clinical examination (Combined radiosurgical approach, IGR). GTV after EBT (45 Gy) plus cis-Platinum was only 2.5 cm, as assessed by clinical examination (B). CTV was 69 cm 3 . Intracavitary brachytherapy dose was 15 Gy and the overall treated volume (60 Gy) was 242 cm 3 . In the pathologic specimen from colpohysterectomy, performed 6 weeks later, no tumour cells were found. 6.2 Definitive Radiotherapy: combination of external beam radiotherapy and brachytherapy The PTV of brachytherapy in principle must encompass the extent of primary tumour plus safety margins. The treated volume is limited by the maximal tolerance of critical organs. Thus, in extended disease, the whole primary tumour extent at diagnosis may not be completely covered by the treated volume but most of it at least. In definitive radiotherapy the target is usually related to the GTV at diagnosis and/or at the time of brachytherapy. If a precise assessment of target and treated volume is aimed at, the GTV at the time of brachytherapy must be used. Target definition may vary depending on gross tumour volume, topography and the treatment strategy chosen. * For stage IA, IB1, the target is the entire cervix with a safety margin into the corpus (half of the corpus), upper third of the vagina and internal third of the parametria. * For stage IB2, brachytherapy is preceded by external beam therapy, which leads to significant tumour shrinkage. * For tumours extending into the proximal part of the parametria (proximal stage II b) the parametria are to be included in the CTV as far as possible taking into account the dose to critical organs. * For tumours extending into the vagina (stage IIA/IIIA), the respective part of the vagina e.g. the upper half or the whole vagina, including safety margins of about 2 - 3 cm, has to be included in the CTV for brachytherapy, depending on the individual pattern of spread. * For tumours extending far into the parametria (distal IIB/IIIB), there is no clear agreement on the determination of the CTV for brachytherapy. Endocavitary brachytherapy alone can only cover the tumour extension which is directly adjacent to the cervix. As brachytherapy usually follows external beam therapy – because of tumour extension not accessible to brachytherapy at the start of treatment -, the GTV at the time of brachytherapy after tumour shrinkage may be used to define the CTV in these cases, taking into consideration the extension of the GTV at diagnosis. As much as