Minimal residual disease (MRD) status pre- and post- high-dose therapy/autologous stem (HDC/ASCT) cell transplantation for multiple myeloma (MM) in the era of novel agents.

Abstract

8605 Background: MRD assayed by multi-parameter flow cytometer (MFC), has prognostic significance after HDT/ASCT for MM (Paiva et. al. 2008). The frequency of MRD negativity (-) after induction therapy using novel agents such as immunomodulatory drugs like lenalidomide (IMiDs), and proteasome inhibitors like bortezomib, is unknown. The impact of HDT/ASCT on MRD status in this patient group has not been studied. Methods: We performed a retrospective study of all MM patients undergoing HDT/ASCT (January 2010 - December 2012) in our institution. No restrictions on inclusion were made based on the International Myeloma Working Group response criteria. All patients had novel agents as part of their initial induction regimen. Statistical analysis was by SPSS software (V 12.0). MRD status was determined by MFC on bone marrow samples pre- HDC/ASCT [M1] and post- HDC/ASCT (D100 [M2] and I year [M3]). MFC was done with antibodies against CD45, CD19, CD138, CD38, CD20, CD56, and anti-k and l cytoplasmic antibodies. Results: MRD status was available on 91 patients pre-transplant. Of these patients, 80 had MFC recorded at M2 and 17 patients had MFC recorded at M3. Fifty-eight percent were male and 76% were Caucasian. Forty percent received IMiDs, while 60% got proteasome based therapies. Of the 91 patients with MRD pre-HDC/ASCT, 58% (53/91) were MRD (-), and of these patients 89% (41/46) remained MRD (-) at M2. 48 patients were MRD positive (+) pre-HDC/ASCT, 58% (20/34) became MRD (-) at M2. Age, cytogenetic risk, disease stage, number of chemotherapy cycles or immunofixation status had no impact on MRD status. There were only 6 relapses in the cohort, thus the impact of MRD status on progression-free survival could not be studied. Conclusions: Novel agents improve depth of response pre-transplant. HDC/ASCT increases MRD negativity post-transplant. MRD status could aid better timing of HDC/ASCT or adoption of a risk-adapted strategy for high-risk patients. MRD status validation in a prospective cohort is underway at our center (NCT01215344). With future follow-up, the impact of MRD on progression-free survival in the era of novel agents will be determined.