I have an 80y old with new diagnosis of smoldering myeloma (15% plasma cells), no CRAB but KLR 0.08. I know she will likely need treatment soon. She also has RA and her Rheum would like to start rituxan and low dose MTX. Hb 10 range when on MTX prior but had B12 deficiency. Will supplementation and holding MTX Hb now 11.9. 1. Is it ok to go ahead with rituxan? 2. He suggested the myeloma may be worsening her RA and so maybe treating the myeloma may in turn help the RA. Thoughts?
Interesting case and we often see autoimmune conditions with precursor plasma cell disorders and it is often difficult to know whether the 2 conditions are related or driving the other. Do you have any other information about her SMM? FISH results? M protein concentration? Involved/uninvolved light chain ratio? If she does not meet high risk per Mayo 2018 "20-2-20" criteria, then she would have a pretty low risk of developing myeloma and I would just focus on treating her RA as you suggest and see if her plasma cell disorder will improve. I would not treat her smoldering myeloma at this time based on what you have shared so far.
[Community Oncologist Response: She is low risk. Normal karyotype and t11,14 on FISH. SPEP and SIFE negative. 24hr urine 105mg monoclonal lambda, involved/un is 11, skeletal survey (-). Assuming her PET is (-) do you agree that this is considered smoldering light chain myeloma?]
Further specialist response: Yes I totally agree. It sounds like she is low risk and I would not treat her SMM and simply observe. I would suggest rheum manage her RA as they would in anyone else and we can monitor her myeloma markers closely.