COMPARATIVE ANALYSIS OF HDR INTRACAVITARY BRACHYTHERAPY FRACTIONATION: IN-VITRO STUDY
Cervical cancer is commonly treated with high dose rate (HDR) brachytherapy. However, the optimal fractionation and dependency on time interval between fractions in HDR intracavitary brachytherapy (ICBT) technique remain controversial. In this study, three types of fractionated irradiation technique were investigated using human cervical cancer (HeLa) cells to determine the most effective fractionation regime that would be implemented in ICBT treatment. HeLa cells were irradiated using HDR remote-afterloading brachytherapy machine with 3 types of fractionation technique; a single fraction, hyperfraction and hypofraction. The fractionated dose used was 9 Gy/fraction with 18 Gy of the total dose. Cell survival curves were obtained from standard clonogenic assay fitted with Pade Linear Quadratic (PLQ) model using OriginPro 9.2 software. Radiobiological analysis of irradiated HeLa cells was performed based on the cell survival curves. The cell survival curves for single fraction, hyperfraction and hypofraction technique indicate the time interval between fractions impacting the cells survival. The survival curve shoulder of single irradiation tends to be constant as the doses increase more than 12 Gy. For hyperfractionation, the shoulder region was wider which indicates the cells have higher survival. Hypofractionated irradiation had steeper shoulder as the dose increase. In this case, the cancer cells may not have chances to recover and have a lower survival fraction. The radiobiological analysis presented by PLQ model shows that hypofractionated irradiation with 9 Gy/fraction delivered in two fractions might be the most effective fractionation to be implemented in cervical cancer treatment using HDR-ICBT irradiation.