Trends in the Incidence of 15 Common Cancers in Hong Kong , 1983-2008

BACKGROUND
The objective of this study WAS to describe cancer incidence rates and trends among THE Hong Kong population for the period 1983-2008.


METHODS
Incident cases and population data from 1983 to 2008 were obtained from the Hong Kong Cancer Registry and the Census and Statistics Department, respectively. Age- standardized incidence rates (ASIR) were estimated and joinpoint regression was applied to detect significant changes in cancer morbidity.


RESULTS
For all cancers combined, the ASIR showed declining trends (1.37% in men, 0.94% in women), this also being the case for cancers of lung, liver, nasopharynx, stomach, bladder, oesophagus for both genders and cervix cancer for women. With cancer of thyroid, prostate, male colorectal, corpus uteri, ovary and female breast cancer an increase was evident throughout the period. The incidence for leukemia showed a stable trend since early 1990 s, following an earlier decrease.


CONCLUSIONS
Although overall cancer incidence rates and certain cancers showed declining trends, incidence trends for colorectal, thyroid and sex-related cancers continue to rise. These trends in cancer morbidity can be used as an important resource to plan and develop effective programs aimed at the control and prevention of the spread of cancer amongst the Hong Kong population. It is particularly useful in allowing projection of future burdens on the society with the increase in certain cancer incidences.


Introduction
Cancer is an eminent health problem, worldwide.Research published in 2010 estimated that, globally, there was 12.7 million new cases in 2008, and the burden of cancer increased as a result of population aging and changes in lifestyle (tobacco and alcohol consumption, nutritional habits, physical activity) that added to those pre-existing risk factors (especially cancerrelated infections) (Ferlay et al., 2010).In Hong Kong, approximately 30% of death due to cancer was of extreme concern during 1981-2008(Centre for Health Protection, 2012).Investigation has shown that the number of new cases of cancer was increasing at a rate of 2% per annum (Law et al., 2007).There were 24 635 new cases (ratio of male to female, 13 139: 11 496) in Hong Kong in 2008, and the top five prevalent cancers were cancers of lung, colorectal, breast, liver and prostate (Hong Kong Cancer Registry, 2012).
With the rapid economic growth and the remarkable development of Hong Kong from a small fishing village into a cosmopolitan metropolitan city, the lifestyle of most citizens changed substantially.With the technological progress, the related morbidity might also have changed.Although there were some case-control studies and epidemiology investigates of cancer morbidity

RESEARCH ARTICLE
Trends in the Incidence of 15 Common Cancers in Hong Kong, 1983Kong, -2008 Wen-Chuan Xie 1 , Man-Him Chan 2 , Kei-Choi Mak 3 , Wai-Tin Chan 4 , Miao He 1 * or mortality; however, they were carried out only for a certain cancer, and used only short-term data or the data was out of date (Leung et al., 2002;Lee et al., 2003;Au et al., 2004;Ho et al., 2004;Tse et al., 2007;Yee et al., 2007;Yee et al., 2010).In order to monitor recent rates and a long-term trend in cancer incidence among the Hong Kong population, we had analyzed the occurrence of cancer morbidity during the span of time from 1983 to 2008 with the use of data from Hong Kong Cancer Registry.
The Hong Kong Cancer Registry was established in 1963 as a population-based cancer registry, and is a member of the International Agency for Research on Cancer (IARC).This registry had access to almost all hospital/laboratory cancer data in both private and public sectors in the territory.It contained a series of comprehensive cross-checking programs to ensure data were highly accurate.First, they were meticulously checked to eliminate duplications by using the Hong Kong Identity Card Number, together with each patient's name and date of birth.Validity of the data was further tested for the combinations of compatibilities of site-gender, site-age and site-pathology.The source of data was documented and histological confirmation traced as far as possible.Original records were checked in case of doubt.

Materials and Methods
The number of morbidity by cancer sites, stratified for gender and 5-year age group for cancer for the period 1983-2008, were derived from vital statistics compiled by the Hong Kong Cancer Registry (Hong Kong Cancer Registry, 2012).Population figures were obtained from census data and inter-census estimates, by calendar year, age and gender.Population censuses of Hong Kong were to be conducted in every 10 years and by-census was held between two census by the Census and Statistics Department (C&SD) (Census and Statistics Department, 2012).
During 1983-2008, two different revisions of the International Classification of Disease (ICD) were used.In Hong Kong, this included ICD-9 from 1983to 2000and ICD-10 for 2000onward (World et al., 1992).Since the differences were minor in various revisions, we recorded cancer sites for analysis included the 15 major cancers: nasopharynx (NPC) (C11), oesophagus (C15), stomach (C16), colorectum (CRC) (C18-21), liver (C22), lung (C33-34), female breast (C50), cervix (C53), corpus uteri (C54), ovary (C56), prostate (C61), bladder (C67), thyroid (C73), non-hodgkin's lymphoma (NHL) (C82-85), and leukemia (C91-95).Age-standardized incidence rates (ASIR) per 100,000 population per year were calculated for all cancers combined stratified classification by gender using the WHO world standard population (Ahmad et al., 2000).A long-term trend in ASIR was analyzed using the Joinpoint regression model (Kim et al., 2000), which change in the annual ASIR was examined by calculating the average annual percent change (APC) and the corresponding 95% confidence interval.This method described changes in data trends by connecting several different line segments on a log scale at 'joinpoints.' Tests of significance used a Monte Carlo permutation method.Joinpoint software 3.5.2from the Surveillance Research Program of the US National Cancer Institute was used for trend analysis (National Cancer Institute, 2012), which analysis commenced with zero joinpoints and tests for model fitted with a maximum of five joinpoints.

Results
Table 1 listed the incidence of ten leading cancers between different genders in Hong Kong from 1983 to 2008.Lung cancer was the leading morbidity in men during the study period, which accounted for 23.18% for the overall cancer incidence cases.With women, breast cancer made up to 18.43% of the cases of all cancers combined.The trend of ASIR for all sites combined in males and females are presented in Figure 1.As for males, the ASIR of overall cancers showed significant decreased by 1.37% per year during the study period.Among females, the ASIR decreased significantly by 0.94% per year until 2003 and then leveled off thereafter.Kong, 1983Kong, -2008 2. With males, the ASIR for lung cancer decreased significantly by 2.08% per year in the study period.As for females, lung cancer became third in morbidity, following breast and colorectum cancer.ASIR of lung cancer showed significant decreased of 1.39% per year since 1996.
Colorectal cancer was the second most frequent cancer for both men and women.With males, ASIR for CRC showed an increasing trend with approximately 0.8% per annum from 1983 to 2008.As for females, ASIR of CRC showed a steady decrease from 1994 to 2008, following the significant increased observed previously by 1.33% per annum.
Liver cancer was ranked third for males and sixth for females throughout the entire 26-year period.With males, ASIR of liver cancer leveled off until 1993, and began to decrease by 2.45% per annum from 1993 to 2008.As for females, ASIR of liver cancer leveled off from 1983 to 1996, and began with a remarkable decreasing trend with 6.6% per annum from 1996 to 2001, and then leveled off from 2001 onwards.
ASIR of nasopharynx cancer decreased significantly by 3.5% per annum for men and 5.4% per year for women during the previous ten years.
There was a significant decreased in cases for stomach and oesophagus cancer, which ASIR for stomach cancer showed a decreasing rate of 2.86% and 2.93% per annum since 1983 for males and females, respectively.With oesophagus cancer, the rates decreased significantly by 4.37% and 4.46% per year from 1986 to 2008 for men and women, respectively.
ASIR for bladder cancer decreased during the study period, with an astonishing decreasing rate of 11.23% and 15.36% per annum since 2003 for men and women, respectively.There was a leveling off of morbidity rates for non-hodgkin's lymphoma since 1986.
ASIR of leukemia showed a decreasing trend of 3.7% and 6.56% per annum until the end of 1990s for males and females, respectively; and then ASIR of leukemia leveled off afterwards.
Prior of 1995, ASIR of prostate cancer showed a steady level, and then began to increase significantly.ASIR increased by 4.6% per annum during the last 10 years.As for females, ASIR of cancer of breast, corpus uteri, ovary showed increasing trend.There were increasing rates of 1.8% per annum for breast cancer, 3.3% per annum for corpus uteri and 0.9% per annum for ovary cancer in the last 10 years.In contrast, ASIR of cervix cancer decreased 4.4% per annum during the last 26-year time period.

Discussion
Understanding cancer trends is momentous in cancer control monitoring and are also used to carry out evaluation for changes in cancer risk, cancer screening programs, and effectiveness of health care (Wingo et al., 2003).This study has presented detailed analysis on the trends of cancer morbidity rates in Hong Kong during 1983Kong during -2008. .Decline trends in morbidity rates of most types of cancer were in the whole study period and were identified for both genders.The over decline for the morbidity rates in recent two decades is mostly attributable to reduce cancers for lung, liver, nasopharynx, stomach, bladder, oesophagus, NHL, leukemia for both genders and cervix cancer for women.But in contrast, colorectum cancer, thyroid cancer, breast cancer, corpus uteri cancer, ovary cancer, prostate cancer showed different trends in the study period.
Lung cancer is the most common cancer for men and ranks third for women.The rates decrease progressively throughout the study period, attributable to the decrease in squamous cell, small cell and large cell carcinoma (Au et al., 2004).Environmental, occupational and socioeconomic factors may be more apparent as etiological factors for lung cancer, and smoking has been consistently established as the main one (Chan-Yeung et al., 2003;Chiu et al., 2004;Wang et al., 2009;Chiu et al., 2010).The trend in morbidity rates has attributed to the effects of the policy of prohibiting smoking by the Government of the Hong Kong Special Administrative Region (HKSAR) since 1983.In 2009, the HKSAR implements the seventh antismoking measures in all public facilities in Hong Kong in order to reduce pollutants that could lead to cancer.
Hong Kong is endemic in chronic hepatitis B virus (HBV) infection, which approximately 85% of liver cancer are hepatocellular carcinoma, as HBV is the main causative agent (Law et al., 2007).Perinatal transmission from mother-to-infant, blood transmission, sexual contact and other body fluids contact may play important roles in spreading the infection in the population.The reduction of liver cancer morbidity since mid-1990s is interpreted as an effect of the decreasing prevalence of HBV.In order to control HBV infection in the vast Hong Kong population, a universal neonatal vaccination program had been launched in 1988, which hepatitis B vaccines are provided to all newborns (Kwan et al., 1997).The HBsAg prevalence follows a continual falling trend since early 1990s in Hong Kong, the current HBsAg carriage rate in the local adult population is estimated to be approximately 8% in 1996, and have since declined to 1.8% by the year 2008 (Kwan et al., 1997;Viral Hepatitis Preventive Service, 2012).
NPC is rare in most parts of the world; however it shows high rates among Cantonese in Southern China and Southeast Asia.The highest rate is noted in Hong Kong, with the third highest ASIR record in the world (Ferlay et al., 2012).Therefore, risk factors for NPC have been established to include environmental risk factors (Epstein-Barr virus (EBV) infection and smoking) and non-viral environmental risk factors (consumption of Cantonesestyled salted food and genetic factor) (Yu et al., 2002;Lu et al., 2005).In this study it is observed that there is a sharp declined trend for ASIR for NPC in Hong Kong during the study period.There is a progressive declination primarily to keratinizing tumors, which is consistent with the declining rate in smoking since the mid-1970s for both genders among Hong Kong population (Tse et al., 2006).Furthermore, with rapid economic development and accompanying improvements in early disease detection and in lifestyle in Hong Kong, the gradual reduction of population exposures to environmental risk factors and non-viral environmental risk factors have contributed to the decreasing trend of other subtypes of NPC.
The trend of morbidity rates from oesophagus cancer and stomach cancer have decreased in the previous two decades.Environmental and lifestyle factors are the two major contributors to the etiology of these types of cancers.Changes in environmental risk factors, such as reduced use of salt, improved food conservation, a more affluent diet with increased consumption of fresh fruit and vegetables and avoidance of smoking are considered to have played vital roles in the reduction of the two cancers morbidity and mortality (Crew et al., 2006;Tse et al., 2007).Besides tobacco smoking, heavy alcohol drinking have been recognized as an other main risk factor for esophageal cancer, yet it is unlikely to be materially involved in the etiology of stomach cancer (Franceschi et al., 1994).The prevalence of alcohol-related drinks consumption in Hong Kong is low, approximately 0.8% of the residents drinks ≥ 50 gm/day (Fu et al., 2004).In addition, some epidemiology studies have reported that alcohol has significant associations with H. pylori infection and stomach and esophageal cancer risk, yet it differs by tumor location and histology (Martel et al., 2005;Fock et al., 2010).The declining trend in ASIR is in line with the decreasing number of H. pylori infection with the rapid socio-economic development of Hong Kong in the last few decades.
Bladder cancer, NHL and Leukemia for men are ranked as three of the top ten cancers over the entire period.Smoking is one of the most common triggering factors for bladder cancer, which more than 50% of all male bladder cancer is attributed by cigarette smoking (Jankovic etal., 2007).The etiology of the most common NHL types remains elusive.Environmental, dietary, immunosuppression and infectious agents have been recognized as the main risk factors for NHL (Müller et al., 2005).Although ASIR is rare, leukemia is the most common type of childhood cancer, accounts for 40% of all cancers diagnosed in children younger than 15 years in Hong Kong (Li et al., 1999).Approximately 90% of Leukemia with an unclear etiology, ionizing radiation is recognized as the main environmental risk factor (Belson et al., 2007).The observation in Hong Kong, showing a decrease in risk (ASIR), probably reflected the improvements in living throughout the period.
Morbidity rates of cervix cancer have been declining.Joinpoint analyses demonstrate that ASIR of cervix cancer declined significantly, by 4.4% per annum from 1983 to 2008.The decreasing trend in ASIR may be due to the introduction of Pap smear since 1960s, and as part of antenatal care in the 1980s (Leung et al., 2006).
Meanwhile, some cancers such as male CRC, thyroid, prostate,corpus uteri, ovary and female breast cancers have increased in ASIR, similar to trend observed in Singapore (Lim et al., 2012).Due to the low alcohol consumption and Trends in the Incidence of 15 Common Cancers in Hong Kong, 1983Kong, -2008 rigorous tobacco control policies, a possible explanation for the increasing is due to the changes to a westernized lifestyle early in the past century.Public-health strategies that promote modest alcohol consumption, smoking cessation, increased physical activity and intake of vegetables and fruits, implement population-based programme of CRC screening likely to have significant benefits at the population level for reducing the incidence of CRC in Hong Kong.Breast cancer remain the most important cancer in women, accounting for more than 18% of all female cancers, with significant increasing trends throughout the whole 26-years time period.These trends seemed to related to change in lifestyle that continuous factors of the factors of the risk of cancer, and certainly to the opportunistic screening in voluntary, self-financed and self-referral basis since the early 1990s of breast cancer among Hong Kong women.Exposure to estrogen, early prematurity, late marriage (27.9 years in Hong Kong in 2000) and delayed menopause may also partly explain the increasing trends of breast cancer (Schmidt et al., 2008).
Our report includes 26 year-period of data, and it is believed that the Figures presented in this study provide a reasonably accurate description of cancer incidence trends and can contribute to a better understanding of cancer incidence patterns in Hong Kong.A declining trend in all cancers combined and in the majority cancers are observed in Hong Kong during the study period.Nevertheless, the aging population and overall increases in risk of cancer have still increased the crude incidence rates and the absolute total number of cancer case.The trend in cancer morbidity can be used as an important resource to plan and develop effective program aiming at the control and prevention of the spread of cancer amongst Hong Kong population.It is particularly useful in allowing projection of future cancer burdens.

Figure 2 .
Figure 2. Observed Standardized (Per 100,000 World Standard) Rates and 'Best' Joinpoint Model Estimates for Cancers that Showed Increased Trend in Hong Kong, 1983-2008.(a) colorectum cancer; (b) Thyroid cancer; (c) prostate cancer and female breast cancer; (d) Corpus uteri cancer and Ovary cancer

Table 2
and 3 listed the results of the Joinpoint analyses by gender and cancer site, applied to morbidity rates from 1983 to 2008.Trends for CRC, thyroid, prostate, female breast, uterine, and ovary cancers are depicted in Figure