Multiple myeloma is the second most common hematologic malignancy in the European Union (EU), responsible for an estimated 21,000 deaths in the EU in 2008. For patients that relapse or are refractory to current standard treatment (combination of bortezomib/lenalidomide, dexamethasone and an alkylating agent) there are few options available and therefore the prognosis within this group is often poor with response to treatment decreasing with successive relapses until resistant disease develops. . Current standard treatment at first relapse in the UK is the use of bortezomib in combination with dexamethasone and cyclophosphamide. Another common treatment is lenalidomide given with dexamethasone and cyclophosphamide. The addition of cyclophosphamide has demonstrated to improve treatment outcomes whilst being tolerated well. A recent clinical study has shown the addition of cyclophosphamide to the combination of pomalidomide and dexamethasone has shown to be safe and tolerable and beneficial in terms of treatment outcomes. The primary aim of this study is to investigate whether the addition of cyclophosphamide to pomalidomide and dexamethasone leads to an improved progression free survival. A secondary aim is to identify markers from clinical material that will predict response to pomalidomide in a group of relapsed and refractory multiple myeloma (RRMM) patients to provide important information for use in discussions with NICE on how best to improve the value and use of pomalidomide in the UK in the RRMM setting.