A Prospective Open-label Single-arm Clinical Study of the Efficacy of Baricitinib for Idiopathic Granulomatous Mastitis in a Single Institution

This study is aimed to explore the treatment effect of baricitinib in idiopathic granulomatous mastitis (IGM), as well as the clinical classification, potential markers and underline etiology of the disease. The target population of interest in this study is patients with non-lactating mastitis, which require core needle biopsy pathology to indicate mastitis without any pathogen infection. When IGM was diagnosed and informed consent complete, low dose of daily 2mg baricitinib was taken orally as the monotherapy in this trial. Follow-up visits were sheduled at baseline (i.e. pretreatment) , 1,3,6 months after treatment, and then every 3 months thereafter until 2 years after treatment discontinuation when achieving complete response. At each follow-up visit, the biggest IGM lesion in each patient was measured by breast ultrasound and 12 inflammational cytokines in peripheral blood should be tested. The primary end point was the objective response rate (ORR) including clinical complete response rate (CR) and partial response rate (PR), and the secondary end point was the recurrence rate within 12 months after drug discontinuation when achieving CR, the degree of inflammation markers decline, and the toxicity and side effects of the drug.