A Safety Confirmation Study on Lenalidomide With Dexamethasone In Japanese Patients With Previously Treated Multiple Myeloma

Inclusion Criteria: * Must understand and voluntarily sign the informed consent form * Age ≥ 20 years at the time of signing the informed consent form * Subjects with previously treated multiple myeloma defined as follows: * Subjects must have received at least 1 prior anti-myeloma drug treatment regimen; and * Considered to have progression of disease (PD) that occurred either during or following the completion of the last anti-myeloma treatment regimen utilized prior to enrollment into this study * Measurable levels of M-protein in serum (greater than or equal to 0.5 g/dL \[5g/L\]) or urine (greater than or equal to 0.2 g excreted in a 24-hour collection sample) * Eastern Cooperative Oncology Group (ECOG) performance status of 0 - 2 * Must be able to adhere to the study visit schedule and other protocol requirements * Females of childbearing potential (FCBP) must agree to use one or more of the following forms of contraception or abstain from heterosexual contact completely and have the male partners use a condom on the occasion of heterosexual contact in the following periods below: * For at least 28 days before starting study drug (in particular, the subject must abstain from heterosexual contact for 2 weeks prior to prescribing lenalidomide). * During the treatment phase (including the dose withholding period) For at least 28 days after the discontinuation/completion of the study drug (Methods of contraception) * Birth control pills * Intrauterine device (IUD) * Bilateral tubal ligation (FCBP must be referred to a health care provider who is familiar with contraceptive methods, if needed). * Male subject must agree to use a condom during sexual contact with female irrespective of pregnancy potential * Subjects must agree that study drug must be immediately discontinued, if pregnancy or a positive pregnancy test does occur in a female study subject or the partner of a male study subject during study participation Exclusion Criteria: * Pregnant or lactating females * Subjects with a history of acute myocardial infarction within the past 6 months before starting the study drugs * Subjects with any history or concurrent conditions of deep vein thrombosis or pulmonary embolus within the past 3 years before starting study drugs * Subjects with tuberculous diseases, herpes simplex keratitis, systemic mycosis or other active infectious diseases * Subjects with non-controlled diabetes, hypertension, digestive ulcer or glaucoma * Subjects with posterior subcapsular cataracts * Subjects with peripheral neuropathy of ≥Grade 2 * Subjects with any history or concurrent conditions which the Principal Investigator / subinvestigators consider inappropriate for participation in this study, and subjects with a serious disease or a mental disease, which is considered to become more risky if the subjects participate in this study. * Subjects with a history of desquamative (blistering) rash while taking thalidomide * Subjects with a history of using lenalidomide * Subjects who have used thalidomide within 28 days before starting the study drugs * Subjects with a history of hypersensitivity to dexamethasone * Subjects who discontinued treatment due to grade 3 or 4 toxicity from high dose dexamethasone * Subjects with a surgical wound after a visceral surgery performed recently * Subjects who have undergone radiation therapy within 14 days before starting the study drugs * Subjects who have used a chemotherapeutic agent, an immunomodulating agent or a study drug (a drug not commercially available) intended for the treatment of multiple myeloma (MM) within 28 days before starting the study drug * Subjects with any history or concurrent conditions of malignancies, other than MM, unless the subject has been free of the disease for 3 years: * Basal cell carcinoma of the skin, * Squamous cell carcinoma of the skin, * Carcinoma in situ of the cervix, * Carcinoma in situ of the breast, * Incidental histologic finding of prostate cancer Tumor, Lymph Nodes, Metastasis (TNM) stage of T1a or T1b) * Known human immunodeficiency virus (HIV) infection or HIV-1 positivity * Subjects who have been diagnosed as an hepatitis b virus (HBV) carrier * Subjects who are applicable to any of the following abnormal laboratory findings: * Absolute neutrophil count : \< 1,000 /μL (1.0×10\^9 /L) * Platelet count: \<75,000 /μL (75×10\^9 /L) * Aspartate aminotransferase (AST)/serum glutamic oxaloacetic transaminase (SGOT) or alanine aminotransferase (ALT)/serum glutamic-pyruvic transaminase (SGPT): \> 3.0 times the upper limit of the standard range * Creatinine clearance: \< 30 mL/min