A new study published in the British Journal of Haematology suggests that the drug combination regimen of Revlimid ^[1] (lenalidomide), cyclophosphamide ^[2], and prednisone ^[3] (RCP) is highly effective in multiple myeloma patients who are refractory (not responsive) to Revlimid-dexamethasone ^[4] (Decadron) treatment.

The researchers of the study had previously shown that continuous low-dose oral cyclophosphamide in combination with prednisone was effective in relapsed multiple myeloma. To further improve the efficacy of the oral regimen, they added Revlimid to the drug combination.

The clinical trial enrolled 14 multiple myeloma patients who were refractory to Revlimid and dexamethasone. Patients received 10 mg Revlimid for days 1 to 21 of a 28-day cycle; 100 mg oral cyclophosphamide daily; and 20 mg prednisone daily. After eight weeks of treatment, the daily dose of prednisone decreased to 10 mg. Patients received a median number of eight courses of treatment. In addition to the RCP regimen, all patients received 100 mg aspirin daily for prevention of blood clots and 480 mg cotrimoxazol daily to prevent infection.

A total of nine patients (64 percent) responded to the RCP treatment, including two patients (14 percent) with complete response, three (21 percent) with very good partial response, two (14 percent) with a partial response, and two (14 percent) with a minor response. Three patients (21 percent) had stable disease, and two patients (14 percent) experienced disease progression.

The two patients who achieved a complete response with the RCP regimen had experienced disease progression when treated with Revlimid and dexamethasone.

The most common severe side effects observed included low white blood cell count (neutropenia), low red blood cell count (anemia), low platelet count (thrombocytopenia), pneumonia, and blood clotting (deep venous thrombosis). In eight patients, the daily dose of cyclophosphamide needed to be reduced by 50 percent due to side effects.

The authors of the study concluded that the RCP regimen demonstrated both low toxicity and high activity in patients who were refractory to Revlimid plus dexamethasone. They suggest that this drug combination should be tested in patients with earlier stage myeloma as well.

According to Dr. Niels van de Donk, one of the lead authors of the study, the researchers are currently preparing a study to test the RCP regimen in myeloma patients with first or later relapse. The team will also evaluate RCP in patients not exposed to Revlimid.

"Depending on the results, testing RCP in newly diagnosed myeloma would be the next step. Because of the effectiveness and good tolerability of RCP, we think that this regimen will be of value as a relapse treatment and possibly also as induction treatment," said Dr. van de Donk.

For more information, please read the original article published in the British Journal of Haematology ^[5] (pdf).