Incidence of second primary malignancy (SPM) in melphalan-prednisone-lenalidomide combination followed by lenalidomide maintenance (MPR-R) in newly diagnosed multiple myeloma patients (pts) age 65 or older.

8007 Background: MM pts have an 8-10 fold higher risk of developing acute myeloid leukemia (AML) than the general population. MM-015 compared MPR-R vs fixed-duration MP or MPR in transplant-ineligible pts ≥65 yrs. This analysis evaluated SPM incidence rates (IRs) and standardized incidence ratios (SIR). Methods: IRs were calculated for AML and solid tumor (ST) malignancies. Expected IRs used to calculate SIR were derived from 23,838 MM pts identified in the Surveillance, Epidemiology, and End Results (SEER) Cancer Registries between 1973-2000 (Dores 2006). Results: As of May 2010 cut-off, total cases of SPM were 4/150 in MPR-R (IR=1.40), 6/152 in MPR (IR=2.05) and 2/153 in MP (IR=0.67), including 2 myelodysplastic syndromes cases in MPR-R and 2 AML cases in each of MPR-R and MPR. 11 pts with complex cytogenetics were randomized to MPR-R/MPR and none randomized to MP. Of these, 3 developed AML; 2 MDS. ST were of heterogeneous tumor types. No B-cell malignancies were reported. Median progression-free survival (PFS) of MPR-R vs MP was 31 vs 13 mos (P < .001; median follow-up: 25 months), with a reduced risk of progression of 60% (hazard ratio HR = 0.395). When SPM were added as additional events for PFS, results remained unchanged (HR = 0.408; P <.001). Conclusions: An imbalance of AML incidence was observed in MPR/MPR-R vs MP, but incidence was low (0.7% vs 0%) and associated with complex baseline cytogenetics. ST IRs were low and similar for all arms. At present, the SPM risk is similar to that reported in other studies. Longer follow-up is needed to definitively assess the risk of SPM in NDMM pts receiving lenalidomide and alkylating agents. Evaluation will continue with updated data at the meeting. Variable MPR-R (n = 150) MPR (n = 152) MP (n = 153) AML PYa 288.47 294.54 301.04 Cases, obs/exp 2/0.42 2/0.43 0/0.44 IRb 0.69 0.68 0 SIR (95% CI) 4.76 (0.80-15.73) 4.65 (0.78-15.37) N/A Solid tumors PYa 286.74 292.40 299.93 Cases, obs/exp 1/4.02 3/4.1 2/4.2 IRb 0.34 1.03 0.67 SIR (95% CI) 0.24 (0.01-1.23) 0.72 (0.18-1.99) 0.48 (0.08-1.57) Abbreviation: CI, confidence interval; PY, person-years. a Double-blind, open-label, long-term follow-up.b Per 100 PY.