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 2cc (D_2cc) 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 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 (TV_H) was 33.7cc ± 10.1cc which was higher than the average TV when the prescription was done at point A (TV_A) of 33.3cc ± 9.4 cc.D_2cc 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.
Conclusion: As observed, average TV, D_2cc of the bladder, and rectum were higher in the case of point H prescription plan (P_H) as compared with point A prescription plan (P_A). The dose difference between P_H and P_A was found to be statistically significant, so careful consideration is needed to implementation of new point H in clinical practice.