Clinical characteristics and outcomes of oligosecretory and non-secretory multiple myeloma.

Secretion of monoclonal immunoglobulins (MIg) detected in the serum and/or urine is one of the typical features of multiple myeloma (MM). However, some patients secrete MIg in quantities below "measurable" (termed oligosecretory MM) and others have no detectable MIgs by standard serum and urine immunofixation (termed non-secretory MM). In a cohort of 852 consecutive patients with active myeloma, we identified 100 (11.7%) patients with oligo/non-secretory MM, including 20 (2.3%) with non-secretory MM. Compared to patients with secretory MM, these were younger, less anemic, and had less often renal dysfunction and less extensive bone marrow infiltration. Presence and extent of bone disease were similar, however, hypercalcemia was less common and more often is ISS (International Staging System)-1 and, in those with available FISH (Fluoresense In Situ Hybridization) , high-risk cytogenetics were less common. FLCs (Free Light Chains) were available in 17 patients with non-secretory MM: only 3 had normal FLC ratio; the others had abnormal ratio and 9/14 had involved FLC ≥ 100 mg/L. The 4-year OS for patients with oligo/non-secretory disease was 64% vs 58% for secretory MM. In multivariate analysis, oligo/non-secretory disease was not an independent prognostic factor per se. Thus, 12% of MM patients present with oligo/non-secretory disease at diagnosis and have different biologic characteristics but similar outcome to other MM patients.