Clinical findings and prognostic factors in chronic myeloid leukemias

Genomic Mechanisms Influencing Outcome in Chronic Myeloid Leukemia

Chronic myeloid leukemia (CML) represents the disease prototype of genetically based diagnosis and management. Tyrosine kinase inhibitors (TKIs), that target the causal BCR::ABL1 fusion protein, exemplify the success of molecularly based therapy. Most patients now have long-term survival; however, TKI resistance is a persistent clinical problem. TKIs are effective in the BCR::ABL1-driven chronic phase of CML but are relatively ineffective for clinically defined advanced phases. Genomic investigation of drug resistance using next-generation sequencing for CML has lagged behind other hematological malignancies. However, emerging data show that genomic abnormalities are likely associated with suboptimal response and drug resistance. This has already been supported by the presence of BCR::ABL1 kinase domain mutations in drug resistance, which led to the development of more potent TKIs. Next-generation sequencing studies are revealing additional mutations associated with resistance. In this review, we discuss the initiating chromosomal translocation that may not always be a straightforward reciprocal event between chromosomes 9 and 22 but can sometimes be accompanied by sequence deletion, inversion, and rearrangement. These events may biologically reflect a more genomically unstable disease prone to acquire mutations. We also discuss the future role of cancer-related gene mutation analysis for risk stratification in CML.

Life Expectancy of Patients With Chronic Myeloid Leukemia Approaches the Life Expectancy of the General Population

PURPOSE

A dramatic improvement in the survival of patients with chronic myeloid leukemia (CML) occurred after the introduction of imatinib mesylate, the first tyrosine kinase inhibitor (TKI). We assessed how these changes affected the life expectancy of patients with CML and life-years lost as a result of CML between 1973 and 2013 in Sweden.

MATERIALS AND METHODS

Patients recorded as having CML in the Swedish Cancer Registry from 1973 to 2013 were included in the study and followed until death, censorship, or end of follow-up. The life expectancy and loss in expectation of life were predicted from a flexible parametric relative survival model.

RESULTS

A total of 2,662 patients with CML were diagnosed between 1973 and 2013. Vast improvements in the life expectancy of these patients were seen over the study period; larger improvements were seen in the youngest ages. The great improvements in life expectancy translated into great reductions in the loss in expectation of life. Patients of all ages diagnosed in 2013 will, on average, lose < 3 life-years as a result of CML.

CONCLUSION

Imatinib mesylate and new TKIs along with allogeneic stem cell transplantation and other factors have contributed to the life expectancy in patients with CML approaching that of the general population today. This will be an important message to convey to patients to understand the impact of a CML diagnosis on their life. In addition, the increasing prevalence of patients with CML will have a great effect on future health care costs as long as continuous TKI treatment is required.

Success story of targeted therapy in chronic myeloid leukemia: a population-based study of patients diagnosed in Sweden from 1973 to 2008

PURPOSE

Chronic myeloid leukemia (CML) management changed dramatically with the development of imatinib mesylate (IM), the first tyrosine kinase inhibitor targeting the BCR-ABL1 oncoprotein. In Sweden, the drug was approved in November 2001. We report relative survival (RS) of patients with CML diagnosed during a 36-year period.

PATIENTS AND METHODS

Using data from the population-based Swedish Cancer Registry and population life tables, we estimated RS for all patients diagnosed with CML from 1973 to 2008 (n = 3173; 1796 males and 1377 females; median age, 62 years). Patients were categorized into five age groups and five calendar periods, the last being 2001 to 2008. Information on use of upfront IM was collected from the Swedish CML registry.

RESULTS

Relative survival improved with each calendar period, with the greatest improvement between 1994-2000 and 2001-2008. Five-year cumulative relative survival ratios (95% CIs) were 0.21 (0.17 to 0.24) for patients diagnosed 1973-1979, 0.54 (0.50 to 0.58) for 1994-2000, and 0.80 (0.75 to 0.83) for 2001-2008. This improvement was confined to patients younger than 79 years of age. Five-year RSRs for patients diagnosed from 2001 to 2008 were 0.91 (95% CI, 0.85 to 0.94) and 0.25 (95% CI, 0.10 to 0.47) for patients younger than 50 and older than 79 years, respectively. Men had inferior outcome. Upfront overall use of IM increased from 40% (2002) to 84% (2006). Only 18% of patients older than 80 years of age received IM as first-line therapy.

CONCLUSION

This large population-based study shows a major improvement in outcome of patients with CML up to 79 years of age diagnosed from 2001 to 2008, mainly caused by an increasing use of IM. The elderly still have poorer outcome, partly because of a limited use of IM.