ESTRO 2025 - Abstract Book

S201

Brachytherapy - General

ESTRO 2025

days, thus considering only patients diagnosed with cancers of the nose vestibule or eyelids, which typically receive 14 fractions administered twice daily (resulting in a total treatment duration of 9 days). The administration of each fraction adhered to our institution's quality assurance program, as detailed in Figure 1A. The Oncentra Brachy TPS (v.4.6.2, Elekta) was utilized to measure the distance between the two buttons on each tube, allowing for a comparison of data between the initial CT scan and the midcourse scan.

Results:

Our study included 30 patients treated with interstitial IRT for cancers of the nose vestibule or eyelids. Each procedure involved an average of 6 plastic tubes per implant. A total of 420 fractions were delivered, and 360 measurements of the button-to-button distance and transverse displacement were recorded using midcourse simulation. Data analysis revealed no significant differences in the mean button distance between the initial CT scan and the subsequent midcourse CT, with mean values of 35.2±10.5 mm and 35.9±10.5 mm, respectively, indicating that the overall results were consistent. For the transverse displacement, no significant differences were observed between the button-to-button distances. However, in 10% of the cases, replanning was necessary, as illustrated in Figure 1B. This decision was based on the criterion that any mean variation in button distance exceeding 1 mm indicated a level of uncertainty that warranted a revision of the treatment plan. Conclusion: The administration of interventional radiotherapy (IRT) for head and neck (H&N) cancers is a complex procedure that requires extensive training for the entire multidisciplinary team involved. Ensuring quality assurance is crucial, not only for patient safety but also to enhance the likelihood of achieving the desired clinical outcomes.

Keywords: interstitial brachytherapy, quality assurance