Epidemiology of Chronic Lymphocytic Leukemia in Taiwan: The Incidence Trend and Its Comparison with That in Caucasian Americans.
Authors: Wu Shang-Ju , Huang Sheng-Yi , Chang Chee-Jen , Tien Hwei-Fang 
Published: October 2019

Abstract
Abstract 4378
Chronic lymphocytic leukemia (CLL) is a prevalent leukemia in western countries. However, the incidence of CLL in Taiwan, is markedly lower but shows an increasing trends. We explored the incidence of CLL in Taiwan during the past two decades and compared it with Caucasian Americans. The epidemiologic data of CLL (1979-2003) in Taiwan was obtained from Taiwan Cancer Registry, and the corresponding data of Caucasian Americans was from the Surveillance, Epidemiology, and End Results Program (SEER). From 1979-2003, the age-adjusted annual incidence (with WHO 2000 standard population) of CLL in Taiwan increased from 0.08 to 0.36 per 100,000 people with about 4.5 folds increment, while that in Caucasian Americans was much higher but remained in steady state in this period (2.6 to 3.1 per 100,000 people). Age-specific incidence rate of CLL plotted by calendar year at diagnosis revealed a stronger period effect in Taiwanese (Figure 1A). The estimation of age-specific annual percentage changes (AAPC) of incidences revealed that, in every age group, the annual increase of the overall incidence throughout the past 2 decades was much higher for Taiwanese compared with that for Caucasian Americans (Figure 1B). Age-specific incidence rates plotted by birth cohort showed that the CLL incidence was higher for later birth cohorts for every age group in Taiwanese but not in Caucasian Americans (Figure 1C). The individual effects of time period and birth cohort on the trends of incidence of CLL in both populations were analyzed using the age-period-cohort analysis for comparison. These analyses showed a much stronger birth-cohort effect on the incidence trend of CLL in Taiwanese than in Caucasian Americans. This strong birth-cohort effect corresponded to the Westernization of lifestyle in Taiwan since 1960. This finding suggests that, in addition to the racial differences of genetic backgrounds that may be responsible for the differences in the CLL incidence, the environmental effects also play some roles. We also analyzed the cytogenetic abnormalities (CA) by conventional cytogenetics (CG) and fluorescence in situ hybridization (FISH) and assessed their clinical significance in Taiwanese patients who were diagnosed and treated at National Taiwan University Hospital. Thirty-nine patients (45.9%) out of 85 patients possessed CG-CA and 58 (69.9%) out of 83 patients had FISH-CA. FISH was more sensitive to detect CA than CG. Those who had neither CG-CA nor FISH-GA had excellent overall survival (OS). Patients with hypodiploidy or complex CG-CA had poorer prognosis than others (p=0.043 and 0.037, respectively). Among those specific chromosome changes detected by CG, trisomy 12 was the most common CA (14.1% among 85 patients). Detection of 17p- by CG was independently associated with poor prognosis. By FISH, 13q- was the most common CA (45.8% among 83 patients), followed by trisomy 12 (20.5%); the frequencies of these two abnormalities were similar to those reported in western countries. Both FISH-CA of 17p- and 11q- were significantly independent factors for poor prognosis. Trisomy 3 was found in five patients; all were of Binet A stage but had a poor prognosis, suggesting that CLL with trisomy 3 may be a distinct disease entity. From these data we conclude that the incidence of CLL in Taiwan was dramatically increased in recent years and was associated with a birth-cohort effect. The CA of CLL in Taiwanese patients are similar to those in Western countries, indicating that although the incidence of CLL is lower in Taiwan than in the West, the pathogenesis of this disease in these two areas is similar. The finding from combined CG and FISH analysis can help predict prognosis. The clinical significance of trisomy 3 in CLL needs to be further investigated.

Disclosures:
No relevant conflicts of interest to declare.