Dosimetric impact of dose constraint indications using individual patient dose management system for brachytherapy in cervical cancer.

Purpose: Total dose assessment for cervical cancer necessitates converting external beam radiotherapy (EBRT) and brachytherapy (BT) doses to equivalent doses in 2 Gy fractions (EQD₂), and compare them with dose constraints. However, this feature is absent in current treatment planning systems. To address this, we developed a system fulfilling this need, and evaluated its dosimetric impact.

Material and methods: The system can assess total dose by considering EQD₂ for targets and organs at risk (OARs), and provide ideal fractionated dose that satisfies dose constraints in each process. The current retrospective study included 82 cervical cancer patients treated with EBRT and four BT fractions. Forty-one patients were assigned to either of two groups (with or without system). These groups were compared with typical dosimetry parameters (DPs) for high-risk clinical target volume (HR-CTV), rectum, bladder, and percentage of dose constraint achievement of DPs to reveal dosimetric impact of the system. Sub-group analysis included 61 patients with HR-CTV doses of < 85 Gy to examine whether treatment planning was adequate with or without the system.

Results: The DP for HR-CTV was similar across BTs, but for OARs, it was statistically significantly lower in the group with system (p < 0.001) than in the other group. Also, the group with system had a higher percentage of cases meeting HR-CTV dose constraints (p = 0.02), with no variation in OARs. Sub-group analysis revealed better adherence to dose constraints in the group with system for each BT compared with the other group.

Conclusions: System usage would facilitate a balanced plan, increasing clinical target volume coverage as much as possible, while considering dose constraints of OARs.