THE ROLE OF DIFFUSION-WEIGHTED MR IMAGING IN EVALUATING THE RESPONSE TO STEROID THERAPY IN IDIOPATHIC GRANULOMATOUS MASTITIS LESIONS

Objective: The aim of this study was to investigate the role of diffusion-weighted magnetic resonance imaging (DW MRI) with an apparent diffusion coefficient (ADC) map in evaluating the re-sponse to treatment of steroid-treated idiopathic granulomatous mastitis (IGM) lesions.Materials and Methods: This retrospective study included 99 le-sions of 58 female patients (average age: 32.91 years; range: 22-55 years) with biopsy-proven IGM. Patients were treated with oral and topical steroids. All pre-treatment and post-treatment MR exam-inations were evaluated. The maximal size of the masses and non-mass enhancement (NME) lesions were measured. Patients were classified as complete response (CR), partial response (PR), and non-response (NR) according to the dynamic contrast-enhanced (DCE) MR findings after treatment.Results: ADC values of areas occupied by IGM (0.933 +/- 0.317x10-3 mm2/sec) were lower than contralateral normal parenchyma (1.259 +/- 0.423x10-3 mm2/sec). Twenty-two (22.22%) of the lesions were in the NR group, 30 (30.30%) in the PR group, and 47 (47.47%) in the CR group. There was no significant difference between the pre-treatment ADC values in NR, PR, and CR groups (p=0.228). There was a significant difference between the pre-treatment and post-treatment ADC values in the PR groups (p=0.001).Conclusion: DW MR imaging in IGM is a useful method to monitor the response to treatment. However, it is not successful in predict-ing response to treatment.