Interfraction physical dose variations in high-dose-rate brachytherapy for carcinoma cervix based on computed tomography image dataset to find the compatibility of the first fraction plan to treat successive fractions

Context: Due to limited resources and/or affordability by majority of the patients, many centers in low- and middle-income countries are still not able to adapt three-dimensional image-based brachytherapy planning in their routine practice. Aim: The aim of the study was to see the feasibility of using computed tomography (CT)-based plan of the first fraction to treat successive fractions of intracavitary brachytherapy based on the estimation of the physical dosimetric differences between successive applications. Materials and Methods: CT image-based brachytherapy plans of 38 patients who received three insertions of intracavitary application with high-dose-rate brachytherapy have been analyzed. Revised plans for the second and third insertions were generated by adapting dwell time and dwell position of the first insertion plan. The dose to point "A" and maximum doses to 2, 1, and 0.1 cc volumes of the rectum and bladder have been used for dosimetric comparison. Results: The statistical differences of mean point "A" doses were observed insignificant except between original and revised plans for the second insertions. The dosimetric differences between consecutive original and revised plans for the bladder and rectum have not shown any significance except minimum dose to 0.1 cc volume of the rectum for the third insertions. Conclusions: Dosimetric deviation for tumor and organs at risk is within acceptable limit while using CT image-based brachytherapy plan of the first fraction for treating successive fractions.