Bortezomib-Based Induction Treatments Improve Outcomes of Newly Diagnosed Multiple Myeloma Patients with High-Risk Cytogenetic Abnormalities

Abstract 781

Aim of the present study was to evaluate the impact of bortezomib-based induction treatments on clinical outcomes of newly diagnosed multiple myeloma (MM) patients with unfavorable cytogenetic abnormalities. For this purpose, we analyzed 590 bortezomib-treated patients who were screened at diagnosis for the presence of del(13q), t(4;14) and del(17p) by fluorescence in situ hybridization (FISH) on highly purified bone marrow plasma cells. Patients were stratified into the following 3 groups based on 1) the absence of any cytogenetic abnormality (n=261, or 44%) or 2) the presence of del(13q) alone (n=175, or 30%) or 3) positivity for t(4;14) and/or del(17p) (n=154, or 26%). In the great majority of the patients, loss of 17p was detected in more than 70% of bone marrow plasma cells, a finding which precluded a comparison with patients carrying del(17p) in a lower percentage of plasma cells. After diagnosis, 218 patients received induction therapy with bortezomib-thalidomide-dexamethasone (VTD), while the remaining 372 patients were treated with bortezomib-melphalan-prednisone (VMP) (n=181) or VMP plus thalidomide (VMPT) (n=191). The median number of bortezomib infusions (1.3 mg/m²) actually received was 24. Baseline characteristics of the 3 groups of patients were comparable, with the exception of a higher frequency of ISS stage 3 among patients with t(4;14) and/or del(17p) as compared with the cytogenetic-negative group (29% vs 17%, respectively; p=0.003). The rates of absence or presence of del (13q), t(4;14) and/or del(17p) were comparable among patients receiving VTD or VMP or VMPT treatments. Best CR to overall treatment protocols was 39% for the cytogenetic-negative group and 44% for high-risk patients carrying t(4;14) and/or del(17p). With a median follow-up of 27.5 months, median PFS was 40.5 months for patients without cytogenetic abnormalities as compared with 34 months for the high-risk group (p=0.7), while it was not reached after 38 months in the group with del(13q) alone (p not statistically significant for comparison with the other two groups). Overall, the frequency of events was 31% for patients without cytogenetic abnormalities or with del(13q) alone in comparison with 38% for those with high-risk cytogenetic profiles (p=0.15). Median OS was not reached in any of the 3 groups. Forty-month projected OS rates were 89% for the cytogenetic-negative group, 81% for the group with del(13q) alone (p=0.6) and 77% for the high-risk group (p=0.003 for comparison between this latter and the cytogenetic-negative group). Patients with t(4;14) and/or del(17p) had a shorter OS after relapse in comparison with the cytogenetic-negative group (20-month projected rates: 60% vs 76%, respectively; p=0.01). To more carefully evaluate the prognostic relevance of high-risk cytogenetic abnormalities, we stratified patients in the high-risk group into the following 3 subgroups: 1) t(4;14)-positive but del(17p)-negative (84 patients); 2) del(17p)-positive in the absence of t(4;14) (54 patients); t(4;14)-positive and del(17p)-positive (16 patients). Median PFS was not reached after 40 months for patients with t(4;14) alone, while it was 33 months for patients with del(17p) alone (p=0.1) and was 18.5 months for those who carried both these abnormalities (p=0.0008 for comparison between these latter patients and t(4;14)-positive patients). Overall, the frequency of events was 30% and 41% for patients carrying either t(4;14) or del(17p), respectively (p=0.13), while it was as high as 69% for patients with both these abnormalities. The 40-month projected OS rates for these 3 subgroups were 79%, 82% and 64%, respectively (p not significant). In conclusion, the present analysis of a large series of newly diagnosed MM patients receiving bortezomib-based induction treatments showed that: 1) del(13q) alone had no adverse effect on both PFS and OS; 2) the presence of t(4;14) and/or del(17p) did not adversely influence PFS, but was associated with a shorter OS, due at least in part to a worse outcome after relapse; 3) in comparison with t(4;14), del(17p) alone did not predicted for shorter PFS and OS, possibly as a result of the relatively long-term exposure to bortezomib); 4) the presence of both del(17p) and t(4;14) was likely to confer a particularly dismal clinical outlook, a finding which needs to be confirmed in larger series of patients.