Bortezomib-Thalidomide-Dexamethasone Incorporated Into Autotransplantation Is Associated with More Favorable Outcomes After Relapse in Comparison with Thalidomide-Dexamethasone Plus Autotransplantation in Multiple Myeloma

Abstract ⁴²¹⁰

In a previous analysis performed with a median follow-up of 36 months (mos), superior CR/nCR rates and extended PFS were demonstrated with bortezomib-thalidomide-dexamethasone (VTD) vs thalidomide-dexamethasone (TD) as induction therapy before, and consolidation after, double autotransplantation (ASCT) for newly diagnosed myeloma (MM). Here we report an updated analysis of that study, including a detailed analysis of outcomes after relapse or progression (R/P), an important issue for patients (pts) who received up-front a triplet novel agent-based therapy incorporated into ASCT. After a median follow-up of 52 mos, continued TTP and PFS benefits with VTD vs TD were demonstrated, while no difference in OS was seen between the two arms. Median PFS for pts randomized to the VTD arm was 56 mos vs 42 mos for those assigned to TD (HR=0.64, p=0.001). Similarly to PFS, median TTP for pts in the VTD group was longer than in the TD group (57 vs 45 mos, HR=0.63, p=0.0006), reflecting a 37% reduction in the risk of R/P with VTD. The probabilities of R/P in the VTD and TD arms were 41% vs 55% (p=0.002). In comparison with the VTD-treated group, a higher percentage of pts in the TD arm required the immediate start of salvage therapy after symptomatic R/P was documented (67% vs 82.5%). By the opposite, the fraction of pts with asymptomatic R/P that did not require any antimyeloma therapy until the cut-off date for the analysis was higher in the VTD arm compared with the TD-treated group (33% vs 17.5%, p=0.016). In these pts, the median interval from the date of R/P to the cut-off date for the analysis was 7 mos for the TD-treated group vs 17 mos for the VTD-treated group. Median time to subsequent antimyelomatherapy (defined as the interval between start of induction therapy and administration of the first dose of second-line therapy) was significantly longer for pts who experienced R/P in the VTD arm in comparison with pts who progressed in the TD arm (35 vs 29 mos, p=0.018). The associated interval between last administration of front-line therapy (e.g. consolidation for pts who received the entire treatment program or every other treatment before consolidation for those who discontinued earlier) and first administration of second-line therapy (salvage therapy-free interval) was 22.5 mos for the VTD-treated group vs 15 mos for the TD-treated group (p=0.009). Both bortezomib and lenalidomide were the most frequently used agents at the time of R/P (82% of all cases), while only 18% of pts were treated with conventional cytotoxic drugs. As expected, the majority of pts in the TD arm received a second-line therapy that included bortezomib (70%), while lenalidomide-dexamethasone was received by 10% of pts. By the opposite, in the VTD arm both bortezomib- and lenalidomide-based salvage therapies were equally distributed (41% vs 39%). The probability to achieve at least a partial response after second-line therapy including bortezomib was 60% for pts with prior exposure to VTD vs 63% for those randomized to TD. No difference in post-R/P OS was demonstrated between VTD-treated and TD-treated subgroups of pts who received bortezomib-based salvage therapy after R/P (2-yr estimates: 48% vs 53%, p=0.59). In the overall population, post-R/P OS was significantly shorter for pts who received salvage therapy with conventional cytotoxic drugs (2-yr estimate: 41%) in comparison with pts treated with novel agents, including bortezomib or lenalidomide (2-yr estimates: 52% and 53%, respectively) (p=0.0001). In conclusion, front-line therapy with VTD incorporated into ASCT was superior in comparison with TD plus ASCT in terms of extended TTP, PFS, time to subsequent antimyeloma therapy and salvage therapy-free interval. VTD-treated pts had a higher probability than TD-treated pts to experience long-lasting asymptomatic R/P not requiring second-line therapy. VTD-treated and TD-treated pts who subsequently received bortezomib-based salvage therapies had similar rates of response and post-R/P OS. This finding suggests that short-term exposure to VTD, as planned in our study, did not favor the selection of bortezomib-resistant clones, thus allowing to rechallenge bortezomib as (part of) second-line therapy after symptomatic R/P.