CT vs. MRI para braquiterapia guiada por imagen en cáncer de cuello uterino localmente avanzado: Un análisis de...

Although MRI is the gold standard for image guided brachytherapy (IGBT) for cervix cancer, CT scan is widely used. However, there is dearth of comparative evidence.

Patients with FIGO (2018) stage IB3 - IVA treated with (chemo)radiation and CT-Ultrasound or MRI-based IGBT from 2016 to 2023 were included. The planning aim was to achieve D90 of ≥ 85 Gy₁₀ to high-risk clinical target volume (HRCTV) and ≤ 90 Gy₃, ≤ 75 Gy₃ and ≤ 75 Gy equivalent dose in 2 Gy (EQD2) to 2cc bladder, rectum and sigmoid, respectively. Propensity score matching (PSM) was performed to compare local control, disease-free survival and adverse events. Univariate and multivariable analyses were performed using log-rank test and Cox Regression model. Post hoc power analysis was performed for non-inferiority margin of 5%, assuming α = 0.15.

Out of the 689 patients, 240 were eligible for PSM (120 each in CT and MRI cohort). Median HRCTV was 34 cc (IQR: 26 - 42). Forty-three percent (n = 104) of patients underwent intracavitary-interstitial brachytherapy (IC-ISBT), whereas others received ICBT. At a median follow up of 35.3 months, there was no difference in 3-year local control (LC) and disease-free survival (DFS) between CT and MRI cohorts [LC: 89% (95% CI: 82-97%) vs. 92% (95% CI: 87-97%) p = 0.71; DFS: 71% (95% CI: 62 - 82%) vs. 73% (95% CI: 65 - 81%), p = 0.86; respectively]. Late grade ≥ 3 gastro-intestinal and genitourinary toxicities were comparable [(8.2 vs. 11%, p = 0.51) and (2.5 vs. 4.2%, p = 0.49)]. The hazard ratio for non-inferiority of CT was 0.84 (95% CI, 0.34-2.07) with power of 0.69.

CT- based brachytherapy may provide comparable outcomes to MRI-based BT. The results of the study should be considered hypothesis-generating needing validation in prospective studies.