Pretreatment MRI parameters as predictive biomarkers for short-term clinical response to dienogest in adenomyosis: a...

To evaluate whether pretreatment magnetic resonance imaging (MRI) parameters can predict short-term clinical response to dienogest (DNG) in patients with adenomyosis.

This retrospective study included 78 patients with MRI-diagnosed adenomyosis who underwent pelvic MRI before hormonal therapy between October 2018 and July 2025. Quantitative MRI parameters included T2 signal intensity ratios, diffusion-weighted imaging (DWI) signal intensity ratios, normalized apparent diffusion coefficient (ADC), and uterine morphological parameters. Adenomyosis subtypes were classified according to the modified Kishi criteria. Short-term clinical response was assessed primarily 3-6 months after treatment initiation as a composite clinical outcome encompassing symptom improvement (dysmenorrhea, menstrual blood loss, and/or hemoglobin levels) and treatment continuation; patients were classified as responders or non-responders. Predictive analyses were restricted to the DNG cohort because only one patient in the GnRH cohort was a non-responder.

Of the 78 patients, 32 received gonadotropin-releasing hormone (GnRH) agonist or antagonist therapy and 46 received DNG. In the DNG cohort, 30 patients were responders and 16 were non-responders. MRI-based adenomyosis subtype, lesion distribution, and uterine morphological parameters were not significantly associated with response in DNG-treated patients. However, absolute ADC values were significantly higher in responders (1.03 vs. 0.89 × 10⁻³ mm²/s, P = 0.036), as was the ADC signal intensity ratio relative to the endometrium (ADC SIR_endo: 0.92 vs. 0.85, P = 0.034). Receiver operating characteristic analysis demonstrated moderate discrimination for both parameters (area under the curve = 0.70). Optimal cut-off values were 0.951 × 10⁻³ mm²/s for ADC and 0.952 for ADC SIR_endo.

Quantitative diffusion MRI parameters were associated with short-term clinical response to DNG, whereas conventional morphological features were not. Diffusion-weighted MRI may provide complementary imaging biomarkers for adenomyosis stratification in DNG-treated patients; prospective validation with longer follow-up is warranted.