Acute Promyelocytic Leukemia Relapse in a Large Medical Center of China over a 9-Year Period: Evolving Treatment Strategies and Lessons for This Highly Curable Disease

All-trans retinoic acid (ATRA)/arsenic trioxide (ATO) combination based therapy has become recommended first line treatment for de novo diagnosed low- to intermediate-risk acute promyelocytic leukemia (APL) patients. Though highly curable, relapses of APL could happen due to various reasons. In this research, we retrospectively analyzed data from patients who were diagnosed and treated APL between 2007 and 2015 in a tertiary hospital in northwest China. 123 APL patients were included, among which, 13 patients experienced relapse despite intensive treatment of ATRA plus ATO or ATRA plus chemotherapy or ATRA plus ATO plus chemotherapy. Although they all achieved complete remission after first induction therapy, 2 patients relapsed during maintenance therapy, 3 patients discontinued treatment then relapsed, 6 patients relapsed during consolidation therapy. Relevant data were subsequently compared with guidelines and multi-centre clinical researches to find out possible reasons of relapse. The results showed, all 13 relapsed patients received less than recommended dose of ATRA and ATO. 6 patients had longer than 4 months' treatment intervals, 4 patients received more than 5 courses of chemotherapy as consolidation or maintenance therapy, among which 2 patients relapsed during maintenance therapy till received chemotherapy 12 and 16 courses respectively. Risk assessment: 5 patients with low-risk, 4 patients with intermediate-risk, 4 patients with high-risk. Conclusion: It is highly possible that the relapse of APL is related to insufficient prescription of ATRA and ATO, and too many courses of chemotherapy may exert negative effects on outcome.