Effect of Venous Thrombotic Events on Overall Survival in Multiple Myeloma: Analysis of Thrombotic Events Occurring in E4A03A Randomized Trial of Lenalidomide Plus High-Dose Dexamethasone (RD) Versus Lenalidomide Plus Low-Dose Dexamethasone (Rd) in Newly Diagnosed Multiple Myeloma, a Trial Coordinated by the Eastern Cooperative Oncology Group (ECOG).