Drug Toxicities in Second-Line Treatment of Chronic Myeloid Leukemia

Introduction

Chronic myeloid leukemia (CML) is known to be a myeloproliferative neoplasm that involves a genetic abnormality defined as Philadelphia chromosome. Part of chromosome 9 becomes attached to chromosome 22, forming the BCR-ABL fusion gene, which is an oncogenic tyrosine kinase. The rise of the tyrosine kinase inhibitors (TKIs) has transformed the outcome of CML. Imatinib was the first TKI approved for treating patients diagnosed with CML in 2001. Dasatinib and Nilotinib were accredited as second-line therapy in 2006 and 2007, respectively, for patients who had failed previous therapy. Although these new drugs improved response compared with imatinib, they also have important side effects that can lead to non-adherence to treatment. Given the importance to maintain regular treatment to avoid disease progression, this paper aims to discuss the drug toxicities in patients undergoing second-line therapy.

Patients and methods

This study was an observational analysis using medical records in Santa Marcelina Hospital, a public service located in São Paulo, Brazil.

Results

A total of 58 CML patients taking second-line therapy were included, 28 with dasatinib and 30 with nilotinib. In dasatinib group, only 3 patients were diagnosed accelerated phase and each one had different side effects, as hematological toxicity, pleural effusion and ulcerative colitis. Of 25 chronic phase patients taking dasatinib, 12 (48%) presented with clinical and laboratorial abnormalities: 3.5% had hematological toxicity (2% with severe bleeding), 4% had cutaneous rash, 10.7% with ulcerative colitis (confirmed in bowel biopsy) and 18% developed pleural effusion. 25% of all dasatinib patient with side effects lost molecular response and started a third TKI.

In nilotinib cohort, 7 patients were diagnosed with CML accelerated phase and only two developed liver toxicity. 23 patients were chronic phase and 60% presented with several side effects: 3% hypertriglyceridemia, 6% had hematological toxicity, 6% with dyspepsia, 10% had cutaneous rash and 27% presented with higher liver transaminase. 7% of all nilotinib patients who developed side effects lost molecular response and had to discontinue therapy.

Discussion

Several examples of side effects can be described with all TKI including cytopenias, fatigue, pain, fluid retention, GI disorders, skin complains, cardiac and liver toxicities but grade 3-4 occurs in less than 2-3% of patients as Jabour et al reported. Despite of important adverse effects, dasatinib and nilotinib induce rapid and durable hematologic and cytogenetic response. In general, the most related toxicities are self-limited and manageable as Kantarjian related. Comparisons between these two second-line therapy using intolerance criteria can be difficult to represent because studies published until now have two different types of population in terms of cytogenetic response achieved previously with imatinib, for example. So, to have a successful treatment, it is important to consider other variables as comorbidities and mutational status as referred Mathisen et al. Individualized risk assessment, between CML and patients characteristics, should influence treatment choices and clinical management.

In conclusion, the efficacy and safety of dasatinib and nilotinib have been confirmed by long-term outcome. Clearly these drugs have unique pharmacologic profiles and response patterns in every single patient, but the goal of treating these patients is the correct management of adverse events without losing molecular response.