Subcutaneous immunoglobulins replacement therapy in secondary antibody deficiencies: real life evidence as compared to primary antibody deficiencies

Secondary antibody deficiencies (SAD) may require immunoglobulin replacement therapy (IgRT). While the intravenous route (IVIG) is broadly considered effective in SAD, the use of subcutaneous immunoglobulins (SCIG) is mainly adopted from the experience in primary antibody deficiencies (PAD), where SCIG have been shown to perform as effective as IVIG. However, evidence-based data on SCIG administration in SAD patients are still insufficient. Herein we retrospectively evaluated the efficacy and safety profile of SCIG treatment in 131 SAD patients as compared to a group of 102 PAD patients. We found SCIG being equally effective in reducing annual infectious rate both in SAD and PAD patients. However, SAD patients required lower SCIG dosage and lower IgG through level to achieve similar biological effect in terms of infection burden, at the steady state. SAD patients also showed better correlation between SCIG dose and serum IgG achieved value. Furthermore, within SAD, SCIG were found to work irrespective of the underlying disease. Especially in Non-Hodgkin Lymphoma patients, whose indication to IgRT is still not included in all guidelines and for whom evidence-based data are still lacking, SCIG were as effective as in Chronic Lymphocytic Leukemia or Multiple Myeloma patients, and SCIG discontinuation, without evidence of B cell recovery, led to IgG decline and relapsed infections. Finally, treatment tolerance in SAD patients was comparable to the PAD cohort. Globally, our data suggest that SCIG, as already appreciated in PAD, represent a valuable option in SAD patients, independent on the disease leading to antibody deficiency