RESUMEN
AIMS: To compare the inter-fraction dose variation for bladder and rectum using a bladder-rectum spacer balloon (BRSB) versus vaginal gauze packing (VGP) in patients treated with high dose rate intracavitary brachytherapy for carcinoma cervix. MATERIALS AND METHODS: After the completion of external radiotherapy, 80 patients were randomised to receive intracavitary brachytherapy using either the BRSB or VGP. The procedure was carried out under general anaesthesia using tandem ovoid applicators. Computed tomography-based planning was carried out and the dose was prescribed to point A. Doses to 0.1, 1 and 2 cm(3) volumes were reported for bladder and rectum for each fraction. The absolute inter-fraction dose variation for each subvolume was compared using the independent sample t-test. RESULT: The mean bladder and rectal volumes, as well as the inter-fraction volume variation, were comparable for the BRSB and VGP. The BRSB resulted in a significant reduction in absolute dose as well as the inter-fraction variation for dose to 2 cm(3) rectum volumes (BRSB 0.80 Gy, standard deviation 0.71 Gy versus VGP 1.16 Gy, standard deviation 0.83 Gy; P = 0.04). Cumulative bladder D2cm(3) doses of more than 90 Gy3 were observed in six patients in the BRSB arm versus four patients in the VGP arm (P = 0.73). In both the arms, the rectal D2cm(3) doses did not exceed 75 Gy3. CONCLUSIONS: Use of a BRSB resulted in a significant reduction in inter-fraction variation in D2cm(3) rectal dose. However, no significant difference in the inter-fraction dose variation for the other subvolumes of bladder and rectum could be shown between the BRSB and VGP. The use of a BRSB may enable rectal dose reduction and inter-fraction variation where anaesthesia is not routinely used or where there is limited physician expertise. The modification suggested in the BRSB may facilitate its additional usage.