Factors affecting the dosimetry of high-dose rate intracavitary brachytherapy in cervical cancer

Background: Intracavitary brachytherapy (ICBT) is essential in managing locally advanced cervical cancer. Brachytherapy as a modality has the advantage of a higher dose to the tumour with a dose fall off at the periphery as per the inverse square law. The dose per fraction is much higher than external beam radiotherapy. So proper application and dosimetry are of paramount importance to reduce late toxicity.Methods: A retrospective analysis of 69 patients who underwent three ICBT applications of 7 Gray in each fraction was done. The factors under consideration were the type of pain management (spinal anaesthesia (SA) versus conscious sedation (CS)), the initial size of the disease (bulky and non-bulky) and subsequent fractions (first fraction versus third fraction). The dosimetric parameters analysed were the doses received by points A, B and P and that of the critical organs (bladder, rectum and sigmoid colon).Results: The dose received by critical organs was comparable concerning all the factors under consideration. The dose to point P on the left side was significantly lower in the CS group than in the SA group (p-value = 0 center dot 031). Also, the dose to point P on the right side was significantly lower in the third fraction compared with the first fraction (p-value = 0 center dot 016).Conclusions: ICBT under spinal anaesthesia resulted in a higher dose to the pelvic wall. The initial size of the tumour or the subsequent fractions does not significantly affect the dose received by critical organs.