Evaluation of Interfraction Dose Discrepancies in Organs at Risk, Clinical Target Volume, and Points A and B in...

Brachytherapy is an integral part of the management of carcinoma cervix. High-dose-rate intracavitary brachytherapy (HDR ICBT) is often delivered after external beam radiotherapy (EBRT) in more than one session. The uncertainties may arise due to variations in anatomy and applicator position during each session, which may impact dose distribution to the clinical target volume (CTV) and normal organs. This study aims to quantify interfraction dose variations in HDR ICBT for cervical cancer patients using computed tomography-based planning.

In this retrospective study, 30 patients with carcinoma cervix of the International Federation of Gynecology and Obstetrics stage IB2 to IVA after EBRT were included in the study. Total dose for ICBT was 21 Gy delivered in 3 weekly fractions. Doses to CTV, Point A, Point B, and normal organs (rectum, bladder, and sigmoid colon) were recorded in each session. Statistical analysis was conducted using the Chi-square test to compare dose variations between fractions, with a significance level set at P < 0.05.

Mean dose received by 90% of the CTV was 5.92 Gy, 5.77 Gy, and 6.05 Gy for the first, second, and third fractions, respectively. Doses to 0.1 cc of bladder were 8.02 Gy, 7.17 Gy, and 7.51 Gy across fractions, whereas for 1 cc, doses were 6.17 Gy, 5.88 Gy, and 6.15 Gy, respectively. For 1 cc of rectum, doses were 5.60 Gy, 4.90 Gy, and 5.23 Gy, and for 2 cc, 5.17 Gy, 4.34 Gy, and 4.71 Gy, respectively, for three fractions. Sigmoid doses had relatively stable dose variation.

Bladder, rectal, and sigmoid doses varied considerably across fractions, emphasizing the need for strict organ preparation protocols and adaptive dose monitoring.