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

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. 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 2cc (D2cc) 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. On average, point H was 4.0mm ± 6.4mm shifted (superior/inferior) from point A, along the tandem direction. The average TV when the prescription was done at point H (TVH) was 33.7cc ± 10.1cc which was higher than the average TV when the prescription was done at point A (TVA) of 33.3cc ± 9.4 cc.D2cc increased from 63% ± 23% to 68% ± 24% for the rectum and 52% ± 18% to 56% ± 20% for the bladder when the prescription point changed from A to H. As observed, average TV, D2cc 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.