How Long Do I Need To Take Immunosuppressive Medicines For Castleman Disease?

hi, i have been diagnosed with castleman disease and they told me i need to take immunosuppressor drug. for how long i need to take them and what are the prognosis . I had done theses tests : HLb5, HLb27, ANCA, PANCA, CANCA , AGPA 210, cryoglobulin, ANA, SSA,SSB, anti CCP(<7) all theses tests came out negative. the doctor said i don't have antoimmune disease but it's the castleman that dysrupting my immune system. i am 37 year old. Also 10 year ago i had a major surgery to remove a mass in my retroperitoneal area . it appeared i had 2 types of mass the bigger one was not removed and it was benign( angiolipome) and the small one was castleman disease on the biopsie and was removed. Thanks