Assessment of rectal dose with thermoluminescent in vivo dosimetry in high-dose-rate cobalt-60 intracavitary brachytherapy for cervical cancer: A two-arm cohort study using orthogonal images planning.

Purpose: High-dose-rate intracavitary brachytherapy delivers high radiation doses to tumors while minimizing exposure to surrounding normal cells. However, inappropriate administration can lead to radiation-induced toxicity by overdosing organs at risk. This study evaluated and compared the rectum doses planned by treatment planning system and measured using a thermoluminescent dosimeter.

Material and methods: Thermoluminescent dosimeters (TLD) were employed to measure radiation dose to the rectum across two patient groups: one treated using first fraction-based planning (FFP), and the other with each fraction planned individually (EFP).

Results: The mean dose measured by TLD (3.99 ±1.63 Gy) was higher than the mean dose planned by TPS (3.23 ±1.16 Gy, p < 0.001). The mean dose difference was higher in second fraction (0.87 ±1.89 Gy) for first fraction-based planning group; however, the differences between first and second fractions were not statistically significant in either group.

Conclusions: For patients transferred from a brachytherapy couch to a hospital stretcher during applicator insertion and dose delivery, first fraction-based planning is feasible. However, caution is needed to minimize applicator shifts, as these changes can alter the geometric position between fractions.