Study of Pomalidomide, Oral Dexamethasone and Very Low-dose Cyclophosphamide in Patients With Refractory Multiple Myeloma Who Have Received Lenalidomide and Bortezomib

"Treatment Phase: Combination of Pomalidomide, Cyclophosphamide and Dexamethasone, days 1-21 every 4 weeks (28 day cycles), up to a total of 8 cycles:~* Pomalidomide: Treatment with Pomalidomide 4 mg / day 1-21 days in 28-day cycles is started. Dose reductions will be made based on the evaluation of hematological and non-hematological toxicity.~* Cyclophosphamide: Cyclophosphamide will be administered 15 mg / day, days 1-28 in 28-day cycles.~* Dexamethasone: Dexamethasone will be administered 40 mg / day, days 1, 8, 15 and 22 in 28-day cycles. In patients older than 75 years the dose will be reduced to 20 mg / day in the same previous schedule.~Maintenance Phase: Combination of Pomalidomide and Dexamethasone. The last doses prescribed in the previous cycle will be maintained."