Dosimetric evaluation of tandem-based cervical high-dose-rate brachytherapy treatment planning using American Brachytherapy Society 2011 recommendations

Purpose This study evaluated dosimetric parameters for cervical high-dose-rate (HDR) brachytherapy treatment using varying dose prescription methods. Methods This study includes 125 tandem-based cervical HDR brachytherapy treatment plans of 25 patients who received HDR brachytherapy. Delineation of high-risk clinical target volumes (HR-CTVs) and organ at risk were done on original computed tomographic images. The dose prescription point was defined as per International Commission in Radiation Units and Measurements Report Number 38 (ICRU-38), also redefined using American Brachytherapy Society (ABS) 2011 criteria. The coverage index (V-100) for each HR-CTV was calculated using dose volume histogram parameters. A plot between HR-CTV and V-100 was plotted using the best-fit linear regression line (least-square fit analysis). Results Mean prescribed dose to ICRU-38 Point A was 590472865 cGy, and to ABS Point A was 59335 +/- 3042 cGy. There was no statistically significant difference between planned ICRU-38 and calculated ABS Point A doses (p=023). The plot between HR-CTV and V-100 is well defined by the best-fit linear regression line with a correlation coefficient of 09519. Conclusion For cervical HDR brachytherapy, dose prescription to an arbitrarily defined point (e.g., Point A) does not provide consistent coverage of HR-CTV. The difference in coverage between two dose prescription approaches increases with increasing CTV. Our ongoing work evaluates the dosimetric consequences of volumetric dose prescription approaches for these patients.