A Comparative Analysis of Different Prescription Points in High Dose Rate Brachytherapy of Cervical Cancer

Introduction: The dose prescription point in high dose rate (HDR) intracavitory brachytherapy (ICBT) of cervical cancer is Manchester point A but the localization of this point has a wider variation. To minimize these variations, the American Brachytherapy Society (ABS) introduced a new definition of point A and named it as point H. In this study, these two points have been compared in terms of dosimetric parameters.Material and Methods: Twenty HDR ICBT of cervical cancer patients were retrospectively evaluated with Manchester point A and ABS point H. Target volume covered by prescribed dose (TV), dose to ۲cc (D۲cc) of the bladder and rectum were noted for both points. Statistical analysis using a two-tailed paired t-test was performed to compare dosimetric parameters of both the points of prescription. The maximum value, minimum value, and mean ± standard deviation along with the p value have been noted.Results: On average, point H was ۴.۰mm ± ۶.۴mm shifted (superior/inferior) from point A, along the tandem direction. The average TV when the prescription was done at point H (TVH) was ۳۳.۷cc ± ۱۰.۱cc which was higher than the average TV when the prescription was done at point A (TVA) of ۳۳.۳cc ± ۹.۴ cc.D۲cc increased from ۶۳% ± ۲۳% to ۶۸% ± ۲۴% for the rectum and ۵۲% ± ۱۸% to ۵۶% ± ۲۰% for the bladder when the prescription point changed from A to H.Conclusion: As observed, average TV, D۲cc of the bladder, and rectum were higher in the case of point H prescription plan (PH) as compared with point A prescription plan (PA). The dose difference between PH and PA was found to be statistically significant, so careful consideration is needed to implementation of new point H in clinical practice.

کلیدواژه ها:

Cervical Cancer ، High Dose Rate ، Brachytherapy ، Manchester Point A ، ABS Point H