Incidence and Management of Relapsed Acute Promyelocytic Leukemia
Authors: Hessenauer Michael R , Farhadfar Nosha , Gangat Naseema 
Published: October 2019

Abstract
Background: Acute promyelocytic leukemia (APL) has a favorable prognosis with high complete remission rates of over 90 percent, with relapse occurring in only 10 to 15 percent of patients. Our objective was to describe the characteristics of relapsed patients and review management of relapsed disease.
Methods:
After institutional review board approval, we searched our institutional electronic database for those 18 years and older with a new diagnosis of acute promyelocytic leukemia between January 1, 2000 and April 30, 2016. We gathered all patient information through electronic chart review.
Results:
Out of 89 patients reviewed, 59 had complete treatment data through induction therapy. Of the 59 patients, with median follow-up of 51 months (range 1-180 months), 7 (11.9%) had relapsed. The median age at APL diagnosis of relapsed patients was 52 years (range: 30-77 years). 6 relapsed patients were intermediate or low risk, and 1 was in the high risk category. 6 relapsed patients received an ATRA and chemotherapy-based induction regimen, and 1 received an ATRA and arsenic-based regimen. Median time to morphological remission was 32 days (range: 22-83 days). 6 of 7 relapsed patients achieved molecular remission. Consolidation regimens included conventional chemotherapy alone (1 patient), ATRA and conventional chemotherapy (4 patients), and arsenic alone (2 patients). Of the 7 relapsed patients, 4 completed maintenance therapy. The median time to relapse from first morphologic remission was 40 months (range: 3-47 months).
6 patients were treated at our institution, and 1 was treated at an outside institution. 2 patients had a molecular relapse, 2 had systemic and central nervous system (CNS) relapse, and 1 patient had an isolated CNS relapse. Treatment regimens at relapse included ATRA and chemotherapy (1 patient), arsenic alone (2 patients), ATRA and arsenic (2 patients), and intrathecal methotrexate with conventional chemotherapy (1 patient). Complications of treatment included infection (2 patients: 1 treated with ATRA and chemotherapy and 1 with intrathecal methotrexate and chemotherapy), thrombotic events (1 patient treated with ATRA and arsenic), rash (1 patient treated with arsenic), and QTc prolongation (1 patient treated with ATRA and arsenic). 5 of 6 patients achieved a molecular remission. Consolidation regimens after reinduction included ATRA and chemotherapy (2 patients), arsenic alone (1 patient), intrathecal methotrexate (1 patient), and ATRA and arsenic (1 patient). Of the 2 patients who had a second relapse, 1 had an isolated CNS relapse, and 1 had a systemic and CNS relapse. Both patients were treated with intrathecal methotrexate and conventional chemotherapy. Due to persistent CNS disease, 1 patient underwent therapy with systemic methotrexate and craniospinal radiation. 1 patient had a third relapse, which was treated with ATRA and arsenic. 4 of 6 patients underwent hematopoietic stem cell transplant, 2 autologous and 2 allogeneic. Of the 7 relapsed patients, 5 are alive, including all 4 patients who underwent transplant. Table 1 provides a detailed summary of the management of relapse in each of these patients.
Conclusion:
Our data are consistent with the reported relapse rate of 10 to 15 percent in APL. Patients who relapse are successfully treated with both ATRA and arsenic-containing regimens. In our cohort, relapsed patients had favorable survival.

Disclosures
No relevant conflicts of interest to declare.