Background: Nearly a third of patients with newly diagnosed myeloma (MM) have a preceding diagnosis of plasma cell proliferative disorder (PCPD), mostly monoclonal gammopathy of undetermined significance (MGUS), smoldering multiple myeloma (SMM) or plasmacytoma. While high dose therapy improves survival in patients with myeloma, it is not clear if patients with preceding PCPD have a different outcome.
Methods and Results: We identified 151 patients with preceding PCPD from among 804 patients undergoing high dose therapy at our institution. These included 59 patients (7.3%) who had a preexisting diagnosis of MGUS, 88 (11%) patients, in whom the diagnosis of MM was preceded by SMM, including 23 patients who also had a preceding MGUS or plasmacytoma. In addition, 27 (3.4%) patients gave a preceding history of plasmacytoma. The median duration from the first diagnosis of a PCPD to that of myeloma was 32.4 months (range, 6.1 to 31 years), and was longer for patients with an initial diagnosis of MGUS compared to those with out preceding MGUS. While response rates including complete responses were generally similar between the two groups of patients, those with any preceding PCPD had a median TTP of 24.2 months (95% CI; 20, 28.3) compared to 17.3 (95% CI; 15.7, 18.8) months for those with no previous history (De novo Myeloma); p = 0.01 (Figure 1). The median OS from transplant for patients with previous history was 63.7 months (95% CI; 50.2, 77.4) compared to 48.3 months (95% CI; 39.7, 56.9) for the de novo group, p = 0.01 (Figure 2). These differences were most striking for those with a preceding diagnosis of MGUS; who had a longer time to progression (27.6 months vs. 17.7 months; p = 0.02), and longer OS from transplant (80.2 months vs. 49.3 months, p = 0.046) compared to those without any preceding MGUS. In a multivariate analysis, transplant within 12 months of diagnosis, lower serum M-protein at transplant, PCLI <1%, absence of cytogenetic abnormalities, achievement of CR, and presence of any preexisting monoclonal disorder prior to diagnosis of myeloma were independently prognostic for risk of post transplant relapse.
Conclusion: Patients with preexisting PCPD at the time of myeloma diagnosis undergoing HDT has a better outcome reflecting more indolent disease and a favorable biology than those presenting with de novo myeloma and no antecedent plasma cell dyscrasia.
Disclosure: No relevant conflicts of interest to declare.
