Automated EQD₂ reporting for cervical cancer high-dose-rate brachytherapy using a standalone ESAPI-based application

Reporting cumulative equivalent dose in 2 Gy fractions (EQD₂) for combined external beam radiotherapy (EBRT) and gynecologic high-dose-rate brachytherapy (HDR-BT) typically requires manual transcription of dose-volume histogram (DVH) parameters from treatment planning system (TPS) into worksheets. This process is time-consuming and prone to transcription errors. This study aimed to develop and validate a standalone application for automated DVH-based EQD₂ reporting in cervical cancer HDR-BT, eliminating manual transcription, improving efficiency, and supporting standardized reporting.

A standalone application (Gy+) was developed in C# using Varian's Eclipse Scripting API (ESAPI v15.5). The application retrieved treatment plan's metadata and DVH data, calculated biologically effective dose (BED) and EQD₂ using linear-quadratic model, and performed parameter-wise EQD₂ summation across EBRT and HDR-BT plans. The output included a standardized PDF report, aligned with ICRU Report 89 (Level 2) and EMBRACE II objectives. Technical verification was performed against an ESAPI reference script, and clinical validation was conducted against the existing manual workflow for 40 patients (154 HDR-BT plans).

Technical verification confirmed identical DVH parameter extraction at ±0.1 Gy, ±0.01 Gy, and ±0.001 Gy, and EQD₂ calculations matched worksheet outputs at the clinical reporting resolution. Clinical validation at the patient level showed median differences of -0.061 Gy for bladder and -0.066 Gy for rectum, with 52.5% and 47.5% agreeing within ±0.1 Gy, respectively. Plan-level analysis showed median differences of -0.013 Gy for bladder and -0.012 Gy for rectum, with 87.0% and 89.6% agreeing within ±0.1 Gy. Reporting time was reduced from approximately 6 minutes to 35 seconds.

Gy+ application provides accurate, efficient, and reproducible automated EQD₂ reporting for cervical cancer brachytherapy, reducing manual transcription and operator-dependent variability, with reporting consistent with ICRU 89 and EMBRACE II guidelines.