A Multi-centre Study of Epidemiology, Characteristics, Treatment and Outcome of Chronic Myeloid Leukaemia in Adults in Hong Kong

Chronic myeloid leukaemia (CML) is a malignant disorder of the haematopoietic system characterized by the presence of the Philadelphia chromosome arising from t(9;22)(q34;q 11).The annual incidence of CML is reported to be around 1-2 cases per 100,000 population.In Hong Kong, the age-standardised incidence rate of CML has remained static in recent years.

However, as the incidence of CML increases with age and Hong Kong has an ageing population, the crude incidence rate is expected to follow a rising trend. On the other hand, the prognosis of CML patients has improved significantly since the advent of tyrosine kinase inhibitors (TKis) more than two decades ago. With the efficacious TKis, CML has changed from a deadly cancer to a treatable chronic condition. It has been shown that life expectancy of CML patients is approaching that of the general population now.The prevalence of CML is expected to rise considerably in view of the increasing incidence in an ageing population and improved prognosis. The Hong Kong Cancer Registry only provides data on the incidence rates of cancers but it has yet to provide cancer prevalence data. A clinical registry is "an organized system that uses observational study methods to collect uniform data to evaluate specific outcomes". A disease registry specifically designed for CML would provide more accurate and comprehensive data and allow an in-depth study of the epidemiology and characteristics of CML in Hong Kong.

At present,there are three TKis approved for front-line treatment of newly diagnosed chronic-phase CML,viz.,imatinib, nilotinib and dasatinib.lmatinib is a first-generation TKI while nilotinib and dasatinib are second-generation TKis (2G-TKI) . Nilotinib and dasatinib demonstrate better in vitro efficacy and achieve molecular responses faster and deeper than imatinib,but these drugs not been proven superior to imatinib in conventional clinical endpoints including overall survival and progression-free survival.Besides, nilotinib and dasatinib are not without side effects and their long-term safety profiles are unclear. For example, nilotinib is associated with increased cardiovascular risk while dasatinib often leads to pleural effusion and less frequently,pulmonary hypertension.The safety of imatinib has been well established over the past 15 years and its side effects are generally considered tolerable. However, the generic formulation of imatinib has been recently introduced to public hospitals and substituted for branded imatinib in CML patients. There have been reports that patient switching to generic imatinib develop adverse drug reactions not experienced with branded imatinib. Other less commonly used therapeutic agents include bosutinib and ponatinib, which still play an important role in the management of CML. Therefore, it is important to determine the "real-world" clinical effectiveness of various drugs, and monitor their side effects and long-term toxicities in a population-based approach.

As physicians in Hong Kong are facing a growing patient population on long-term TKI,the demand on health care services and financial burden of drug costs will escalate accordingly. lt is pivotal for the investigators to understand the disease and patients in the locality better by systematic data collection, in order to improve quality of care, allow service planning and facilitate medical research and advances .