Abstract
Survival has increased dramatically for patients with chronic phase chronic myeloid leukemia (CP-CML) using BCR-ABL targeted tyrosine kinase inhibitors, such that life expectancy is expected to approximate that of patients without CP-CML. Randomized controlled trials (RCTs) and observational studies provide valuable insights into the management of chronic diseases such as CP-CML. RCTs are undoubtedly the backbone of clinical research, and the 'gold standard' for evaluating the efficacy and safety of new therapies. However, many questions surrounding the optimal management of patients with CML remain unanswered, and it is widely accepted that these questions will be best answered by evaluating the use of available therapies in clinical practice. Observational studies can extend the knowledge base beyond the clinical trial setting and thus capture a more accurate picture of everyday clinical practice, particularly patients' experiences of long-term CML treatment. There is therefore growing interest in and appreciation of the value of observational research. This review article will examine the relative merits of RCTs and observational studies in the setting of CML, highlighting those factors - such as the advancing age of the CML patient population and growing importance of patient-reported outcomes - that mean that observational studies should play an important role in shaping clinical practice. This article also provides an overview of what observational studies have told us thus far about the optimal management of patients with CML, outlines some of the key remaining unanswered clinical questions in CML, and summarizes ongoing observational studies designed to provide answers to these key questions.