Thalidomide Based Regimens (TBR) for Relapsed/Refractory Multiple Myeloma Patients: Long Term Follow Up, Unmaintained Remissions and Disease Control after Subsequent Treatments.

Introduction: The effectiveness of thalidomide based regimens (TBR) in patients with relapsed/refractory multiple myeloma is well established. However, there are still limited data regarding the long term follow up after such regimens and the outcome of patients when they progress and they receive further treatment. In order to answer these questions we evaluated a series of 114 patients with relapsed/refractory multiple myeloma who were treated with TBR. None of these patients had previously received thalidomide, bortezomib or lenalidomide.

Patients and Methods: All patients were treated with thalidomide and dexamethasone with or without other oral agents. More specifically 41 patients had received continuous thalidomide and pulse dexamethasone, 25 patients clarithromycin, continuous thalidomide and pulse dexamethasone, 43 patients intermittent thalidomide, pulse dexamethasone and cyclophosphamide and 5 patients continuous thalidomide, pulse dexamethasone and cyclophosphamide. Type of treatment at the time of progression after TBR, response to this treatment and progression free survival were recorded for each patient. Moreover, patients who received novel agents after progression to TBR, were divided into 2 subgroups, according to their resistance to thalidomide. In group A, patients had refractory or progressive myeloma while on TBR or within 2 months after discontinuation of TBR. In group B, myeloma progressed more than 2 months after discontinuation of TBR.

Results: Among the 114 patients, 41 had not responded to TBR and 73 (64%) had achieved at least a partial response. The median PFS for all patients was 8 months. As of June 2007, 10 patients remain without progression from 28 to 81 months (median 54 months). Eight patients remain off treatment and without progression for a median of 56 months (range 28–81). Patients who did not respond to or progressed after TBR were analyzed for further treatment and outcome. Thirty eight patients (37%) died before receiving further treatment, 23 patients (23%) received conventional chemotherapy and 41 patients (40%) received continuous thalidomide and dexamethasone +/− clarithromycin or cyclophosphamide (17 patients), bortezomib and dexamethasone (7 patients), melphalan-bortezomib-dexamethasone and intermittent thalidomide (12 patients) or lenalidomide with dexamethasone (5 patients). Among these 41 patients, 24 were classified in group A (thalidomide resistant) and 17 in group B. Overall 17 (41%) achieved at least partial response after retreatment with novel agent-based regimens. A response was observed in 46% of patients in group A and in 35% of patients in group B. The median progression free survival of the 41 patients who received retreatment with novel agents was 9.2 months and the median survival was 17 months. Among the 23 patients who received conventional chemotherapy only five (21%) patients responded and the progression free survival and the median survival were 5.3 and 10.2 months, respectively.

Conclusions: After an oral TBR regimen 6 (5%) patients remain without treatment and free of progression for more than 4 years. A significant number of patients who progressed after TBR and who received further treatment which included a novel agent achieved a response, including several patients who were resistant to TBR.