Dosimetry evaluation and uncertainty analysis of Cobalt-60 HDR brachytherapy for cervical cancer in resource-limited settings.

Background: High-dose-rate (HDR) brachytherapy is essential in the treatment of locally advanced cervical cancer. While Iridium-192 (Ir-192) is commonly used, its short half-life imposes logistical and financial constraints, particularly in low- and middle-income countries (LMICs). Cobalt-60 (Co-60), with a longer half-life and lower operational costs, is a viable alternative. This study aims to evaluate the dosimetric performance and planning uncertainties associated with Co-60 HDR brachytherapy.

Methods: A retrospective dosimetric analysis was conducted on 30 patients with FIGO stage IIB-IIIB cervical cancer, eligable for Brachytherapy, were treated using CT-guided intracavitary HDR brachytherapy with Co-60 sources. Treatment plans were assessed for high-risk clinical target volume (HR-CTV) coverage (D90, D80), dose-volume histogram parameters, and organ-at-risk (OAR) doses (D2cc for bladder, rectum, and sigmoid). Plan quality indices including conformity index (COIN), dose homogeneity index (DHI), and dose non-uniformity ratio (DNR) were calculated. Uncertainty analyses accounted for treatment planning system (TPS) variability and applicator positioning.

Results: The mean HR-CTV D90 was 6.97 Gy, achieving 99.6% of the prescription dose. The mean D2cc values were 5.73 Gy for bladder (81.9%Rx), 4.72 Gy for rectum (67.4%Rx), and 3.23 Gy for sigmoid, all within acceptable tolerance limits. The mean COIN was 0.292, DHI 0.31, and DNR 0.69, indicating moderate dose conformity and acceptable inhomogeneity. TPS and applicator uncertainties contributed to estimated dose deviations of ± 2% and ± 1 mm, respectively.

Conclusion: Cobalt-60 HDR brachytherapy provides clinically acceptable dose coverage and OAR sparing, with dosimetric outcomes comparable to Ir-192. Its longer half-life offers practical advantages for LMICs. Optimization of dose distribution and further validation through Monte Carlo simulations and prospective clinical studies are recommended.