Diffusion kurtosis imaging-assisted MRI for assessing pathological safe-distance status and fertility-sparing feasibility in FIGO stage IB cervical cancer: a prospective single-center study

Accurate preoperative assessment of tumor-internal os distance (TID) is essential for selecting candidates for fertility-sparing surgery in early-stage cervical cancer. This study evaluated the interobserver agreement of DKI-assisted MRI-based TID measurements and their diagnostic performance for pathological safe-distance status and fertility-sparing feasibility in FIGO stage IB cervical cancer. Patients with stage IB cervical cancer who underwent preoperative pelvic MRI with sagittal DKI between September 2016 and June 2026 were prospectively enrolled. TID was measured using sagittal T2-weighted imaging alone (T2WI_TID) and DKI-assisted MRI (MR_TID). Interobserver agreement, diagnostic performance for pathological safe-distance status and final fertility-sparing feasibility, and model performance were evaluated. A prediction model was developed in a training cohort and tested in an internal testing cohort. A total of 170 patients were included. MR_TID showed higher interobserver agreement than T2WI_TID (intraclass correlation coefficient, 0.894 vs. 0.802). For binary pathological safe-distance status, MR_TID showed better discrimination than T2WI_TID (area under the receiver operating characteristic curve, 0.946 vs. 0.840; P < 0.001). For final fertility-sparing feasibility, MR_TID also outperformed T2WI_TID (0.877 vs. 0.806, P = 0.021), with an exploratory cutoff of 10.5 mm. A model incorporating MR_TID, MR-based tumor diameter, deep stromal invasion, parametrial invasion, and lymph node metastasis showed good discrimination in the training and testing cohorts (area under the receiver operating characteristic curve, 0.921 and 0.900, respectively). DKI-assisted MRI improved TID measurement reproducibility and binary pathological safe-distance discrimination, although its role in fertility-sparing selection requires external validation.