Fulminant Onset of Acute Leukemia (FOAL) After Total Therapies (TT) for Multiple Myeloma (MM): Absence of MDS Pathological Criteria within 3 Months of Prior MM Follow-up
Authors: Singh Zeba N , Sawyer Jeffrey R , Post Ginell R. , Waheed Sarah , Usmani Saad Z , van Rhee Frits , Barlogie Bart 
Published: October 2019

Abstract
Abstract 1458

Background:
Cytogenetic abnormalities (CA) in therapy-related myeloid neoplasms (t-MN) usually correlate with nature of previous therapy and clinical presentation. t-MN following prior therapy with alkylating agents and/or radiotherapy are associated with a long latency period (> 3 years) an antecedent myelodysplastic syndrome (MDS) phase, and unbalanced translocations or a complex karyotype. Majority of t-MNs that initially present as acute leukemia (AL) are associated with prior topoisomerase II therapy, a shorter latency period (1–3 years), lack of MDS phase and balanced translocations, commonly involving 11q23/MLL gene. In our experience the usual course of t-MN in MM patients is a prolonged MDS phase with progressive cytopenia, progressing to acute myeloid leukemia (AML) in a subset of patients. Here we report on 7 patients in complete remission (CR) for MM without cytopenia or morphologic evidence of dysplasia on bone marrow evaluation within 3 months prior to presenting with FOAL. One patient developed FOAL within 2.5 months of first documentation of MDS-associated CA (MDS-CA).

Methods:
Of 3890 patients at the University of Arkansas who had received melphalan-based autograft supported high dose therapy, 69 patients developed t-MN— 63 initially presented with MDS and 13 progressed to AML. Six of the seven patients had no prior MDS-CA or morphological dysplasia, and one with MDS-CA seen <2.5 months earlier, had fulminant onset of AL. All BM specimens at time of FOAL and within one-year period prior to FOAL were evaluated. Metaphase cytogenetic analysis was performed on unstimulated BM specimens using standard techniques. Interphase FISH was performed on BM samples using probes to detect CA commonly observed in MDS and AML.

Results:
All FOAL patients were treated on Total Therapy (TT) protocols for newly diagnosed MM including 3 on TT2 with thalidomide arm, 3 on TT3A with VTD maintenance, and 1 on TT4 with VRD maintenance. At the time of FOAL all patients were in CR for MM and on maintenance therapy with dexamethasone, thalidomide, lenalidomide, and bortezomib in combination or as single agents. The clinical and laboratory features prior to and at onset of AL are shown in the table.

Conclusion:
In this cohort, MDS-CA (+8, del20q, −7, del7q, −5, del5q and complex karyotype) were detected in leukemic blasts in 5 of 7 patients with abnormalities of chromosomes 5 and 7 most commonly seen. In contrast to clinical and cytogenetic associations described for t-MN initially presenting as AL, none of our patients showed balanced chromosomal translocations involving 11q23, and all but one (patient 3, 9.5m) had a long latency period of 5 to 10yr. Importantly, the absence of MDS-CA on prior bone marrow evaluations in 6 of 7 of our cases indicates that FOAL cannot be predicted based on surveillance BM metaphase cytogenetics or FISH. Studies using gene expression profile analysis of CD34 stem cells are underway to identify molecular alterations leading to FOAL. Results of these studies may improve t-MN surveillance.

Disclosures:
No relevant conflicts of interest to declare.