Maintenance therapy with thalidomide ^[1] (Thalomid) improves progression-free survival of multiple myeloma patients but has no impact on overall survival, according to a recent study. Additionally, patients with an aggressive form of myeloma show no benefit from this treatment. The findings were presented by Dr. James Child of the United Kingdom’s Clinical Trials Research Unit at the European Hematology Association (EHA) annual meeting in Barcelona on June 13.

Maintenance therapy is long-term, often low-dose and continuous, treatment given to prevent relapse in myeloma patients who have achieved remission. Until recently, use of maintenance therapy was limited to clinical trials. However, results from recent studies have indicated significant benefits of maintenance therapy, and it is being used more frequently. The authors of the current study wanted to investigate whether thalidomide maintenance benefits certain myeloma patients more than others.

The 820 myeloma patients enrolled in the study first received an induction treatment, an initial treatment designed to get myeloma cells under control. The younger and healthier patients underwent a more intensive induction treatment than older or less healthy patients. The researchers did not provide the protocols for induction treatment or the response rates after this phase of treatment.

After induction, half of the patients received thalidomide as maintenance therapy and the other half did not receive maintenance therapy. For those patients who received thalidomide maintenance, the initial dosage of 50 mg daily was later increased to 100 mg daily.

Thalidomide maintenance therapy significantly improved patients’ progression-free survival (the percentage of patients who are alive and have not experienced disease progression a given length of time after the start of treatment). Two years after the start of maintenance therapy with thalidomide, 13 percent more patients were alive and experienced no disease progression compared to patients who received no maintenance therapy. This 13 percent increase in progression-free survival continued five and a half years after treatment (the current maximum follow-up time).

Maintenance therapy with thalidomide did not, however, impact the patients’ overall survival.

Previous studies have indicated that patients with an aggressive form of myeloma, determined by certain unfavorable genetic variations, are at a higher risk for complications and have a shorter survival than other myeloma patients. To determine if these genetic variations affected patient response to thalidomide maintenance therapy, researchers performed genetic analyses to identify groups of patients with and without such variations. Patients were classified as high-risk if unfavorable genetic variations were found or standard-risk if they were not found.

The researchers observed that maintenance thalidomide increased progression-free survival in standard-risk patients but had no effect on progression for the high-risk group. Furthermore, thalidomide may have decreased the overall survival of high-risk patients, although the data was not conclusive.

The researchers additionally noted that among patients who relapsed, survival was better among the patients who had not received thalidomide maintenance, particularly among the high-risk patients. This is possibly due to thalidomide-resistance among the patients who had received thalidomide maintenance. Additionally, many of these patients, who are from Europe, may not have had access to Revlimid ^[2] (lenalidomide) and Velcade ^[3] (bortezomib) as treatment options once thalidomide failed.

Based on these results, the researchers concluded that maintenance thalidomide significantly improves progression-free survival, particularly for standard-risk myeloma patients. However, there was no impact on overall survival due to poor survival after relapse, particularly in those patients identified as high risk.

For more information, please see abstract 1095 ^[4] at the EHA meeting ^[5] website.