We present thrombosis outcome data from Myeloma IX (n=1936) and Myeloma XI (n=4358), phase III randomized controlled trials for NDMM, treating transplant-eligible and ineligible patients before and after publication of thrombosis prevention guidelines.
In Myeloma IX, compared to CTD (cyclophosphamide, thalidomide and dexamethasone), transplant-eligible patients randomized to CVAD induction (cyclophosphamide, vincristine, doxorubicin and dexamethasone) had higher VTE risk (22.5%(n=121/538) vs 16.1%(n=89/554), aHR:1.46,95%CI:1.11-1.93). For transplant-ineligible patients, compared to MP (melphalan and prednisolone), patients randomized to CTDa (attenuated CTD) induction had higher VTE risk (16.0%(n=68/425) vs 4.1%(n=17/419), aHR:4.25,95%CI:2.50-7.20).
In Myeloma XI, there was no difference in VTE or arterial thrombosis risk between transplant-eligible pathways, CRD (cyclophosphamide, lenalidomide and dexamethasone) and CTD (VTE:12.2%(n=124/1014) vs 13.2%(n=133/1008), aHR:0.92,95%CI:0.72-1.18; arterial events:1.2%(n=12/1014) vs 1.5%(n=15/1008), aHR:0.80,95%CI:0.37-1.70). For transplant-ineligible patients, there was no difference in VTEs between CRDa (attenuated CRD) and CTDa (10.4%(n=95/916) vs 10.7%(n=97/910), aHR:0.97, 95%CI:0.73-1.29). However, arterial risk was higher with CRDa than CTDa (3.1%(n=28/916) vs 1.6%(n=15/910), aHR:1.91,95%CI:1.02-3.57).
Thrombotic events occurred almost entirely within 6m of treatment initiation. Thrombosis was not associated with inferior progression-free or overall survival (OS), apart from inferior OS for patients with arterial events (aHR:1.53, 95%CI:1.12-2.08) in Myeloma XI. The Myeloma XI trial protocol incorporated IMWG thrombosis prevention recommendations and compared to Myeloma IX, more patients were on thromboprophylaxis (80.5% vs 22.3%) with lower VTE rates for identical regimens (CTD:13.2% vs 16.1%, CTDa:10.7% vs 16.0%). However, thrombosis remained frequent in spite of IMWG-guided thromboprophylaxis, suggesting new approaches are needed.