Cervical Cancer Brachytherapy Dose Escalation Protocol: Analysis of Early Data Treatments According to EMBRACE II...

Cervical cancer is one of the most prevalent malignancies among women, particularly in developing countries. The combination of external beam radiotherapy (EBRT) and brachytherapy (BT) is the preferred treatment modality for patients with advanced-stage disease. High-dose rate brachytherapy (HDR BT) plays a crucial role in the overall treatment by delivering high radiation doses to the target volume while minimizing exposure to surrounding healthy tissues.

The statistical analysis focuses on the correlation of dosimetric parameters with dose constraints and the incremental dose increase per BT session. Additionally, it compares the total dose received by each patient from EBRT and BT in the high-risk clinical target volume (HR-CTV) and organs at risk (OARs) with the dose constraints of the modern EMBRACE II (European study on MRI-guided BRAchytherapy in locally advanced CErvical cancer) protocol. This study aims to highlight the significance of BT in cervical cancer treatment and provide insights to enhance treatment efficacy.

This study retrospectively analyzed the treatment data of 34 patients with locally advanced cervical cancer. Each patient initially received EBRT, followed by three HDR BT sessions, with the dose per session initially set at 7 Gy and later increased to 8 Gy. Data for this study were collected using a treatment planning system (TPS) software. For each patient, the dose received by 90% of the HR-CTV (D90) and the dose received by the 2 cc volume of each OAR (D2cc) were recorded and converted to an equivalent dose in 2 Gy fractions (EQD2) using α/β=10 Gy for the tumor and α/β=3 for each OAR.

The mean D90 for HR-CTV increased significantly with the transition from 7 Gy to 8 Gy per fraction, resulting in improved target coverage. A total of seven out of 34 treatment plans achieved the recommended-acceptable total dose limit (EBRT + BT) ≥ 85 Gy EQD2 for HR-CTV, and 13 out of 34 treatment plans achieved a total dose between 80 and 85 Gy. For all 34 treatment plans, the OARs complied with the EMBRACE II dose constraints: D2cc < 90 Gy for the bladder, < 75 Gy for the rectum, and < 70 Gy for the sigmoid.

The dosimetric results indicate that CT-based BT (IBBT) planning can achieve adequate tumor coverage while maintaining OAR doses within the acceptable limits of the EMBRACE II protocol. These findings support the ongoing optimization of individualized treatment planning and highlight the importance of having commonly defined limits that are regularly updated.