Background: Secondary primary
malignancies (SPM) have attracted increasing attention with the application of autologous
hematopoietic stem cell transplantation (ASCT) and novel agents in
multiple myeloma (MM). Secondary
acute lymphoblastic leukemia (sALL) has rarely been reported, and the clinical characteristics and prognosis of sALL have not been described in detail. Methods: We retrospectively enrolled 179 consecutive newly diagnosed
multiple myeloma (NDMM) patients undergoing
bortezomib-based induction regimens followed by upfront ASCT and maintenance
therapy from December 2006 to April 2018 in our center. Results: The median follow-up interval was 69.1 months, and 12 patients (6.7%) developed sALL during maintenance
therapy. The median time from the diagnosis of MM to the occurrence of sALL was 51.1 (31.7-91.5) months. All sALL patients received
thalidomide as maintenance
therapy before the onset of sALL, and the median duration of
thalidomide maintenance was 39.5 (24-74) months. The cumulative incidence of sALL was 6.6% and 11.2% at 5 and 10 years after the diagnosis of MM, respectively. All sALL patients presented with a B-cell immunophenotype accompanied by myeloid
antigen expression according to flow cytometry analysis, and the BCR/ABL fusion gene was all negative. Only one patient had evidence of active MM, and the other patients were in stable status at the time of the diagnosis of sALL. The prognosis of most sALL patients was very poor, and the median overall survival time was 11.9 (1.1-51.2) months since the diagnosis of sALL. Conclusions: sALL should be considered for MM patients who developed unexplained persistent
cytopenia while on long-term
thalidomide maintenance treatment, particularly if it has been more than 3 years. With the increasing availability of new drugs for MM,
thalidomide may be recommended for no more than 3 years. Sequential allogeneic
hematopoietic stem cell transplantation was considered as soon as possible after achieving remission in order to achieve a longer survival.