Cancer statistics in Korea: incidence, mortality and survival in 2005.

Cancer has been the most common cause of death in Korea since 1983 and is a major public health concern. This paper overviews the nationwide cancer statistics, including incidence, mortality, and survival rates, and their trends in Korea. In 2005, 142,610 new cancer cases and 65,117 cancer deaths occurred in Korea. The incidence rate for all cancer combined increased by 2.6% annually from 1999 to 2005. Significant increases have occurred in the incidence of colorectal, thyroid, female breast, and prostate cancers. The number of cancer deaths has increased over the past two decades, due mostly to population aging, while the age-standardized mortality rates have decreased in both men and women since 2002. Notable improvement has been observed in the 5-yr relative survival rates for most major cancers and for all cancer combined, with the exception of pancreatic cancer. The nationwide cancer statistics in this paper will provide essential data for evidence-based decisions in the national cancer control program in Korea.

INTRODUCTION

Cancer has been the most common cause of death in Korea since 1983 (1) and poses a major public health concern. Over 140,000 new cancer cases are diagnosed annually in Korea and one out of four deaths results from cancer (2, 3). This paper gives an overview of the nationwide cancer statistics, including the incidence, mortality, and survival rates, and their trends in Korea. This report is a part of Special Article series that presents the annually updated nationwide cancer statistics in Korea.

MATERIALS AND METHODS

Data sources

The Korea Ministry of Health and Welfare started a nationwide, hospital-based cancer registry called the Korea Central Cancer Registry (KCCR) in 1980. Details of the history, objectives, and activities of the KCCR have been documented (4). Incidence data from 1999 to 2005 were obtained from the Korea National Cancer Incidence Database (KNCI DB). Cancer cases were classified according to the International Classification of Diseases for Oncology 3rd edition (5) and converted according to the International Classification of Diseases 10th edition (ICD-10) (6). The survival analysis used 1,151,789 cancer cases first diagnosed during 1993-2005 from the KNCI DB, and followed vital status through 31 December 2006.

Mortality data from 1983 to 2005 were obtained from the Korea National Statistics Office (KNSO) (1). Cause of death was coded and classified according to the ICD-10. The population data were also obtained from KNSO using the resident registration population on 1 July.

Analysis

Crude rates (CRs) and age-specific rates of cancer incidence and mortality were calculated. Age-standardized rates (ASRs) were determined using the World Health Organization (WHO) world standard population (7). The cumulative risks of cancer incidence, which are the probability of developing cancer to the life expectancy, were also calculated. Changes in the annual age-standardized cancer incidence rates were examined by calculating the annual percentage change (APC) over a time period as 100(e-1), where e is the slope of the regression of log age-standardized rates on a calendar year (8).

The survival duration of each case was determined as the time difference between the date of initial diagnosis and the date of death, date of loss to follow-up, or closing date for follow-up. Observed survival rates were calculated using a life table method and relative survival rates were examined with the Ederer II method (9) using an algorithm written in SAS by Paul Dickman (10), with some minor adaptations.

SELECTED FINDINGS

Incidence

Table 1 presents the number of new cancer cases during 2005 in Korea by sex and cancer site. In 2005, 142,610 cancer incident cases were observed. The CRs of all sites combined were 317.8 and 268.0 per 100,000 in men and women, respectively, and the ASRs of all sites combined were 303.5 and 201.4 per 100,000 (Table 2). The cumulative risks for developing a cancer to the life expectancy were 32.3% for men and 26.5% for women.

Table 1

Number of cancer cases and deaths by sex during 2005 in Korea

*Includes gallbladder and other/unspecified parts of biliary tract.

CNS, central nervous system.

Table 2

Crude and age-standardized cancer incidence rates by sex during 2005 in Korea

*Age-standardized to the WHO world standard population; †Includes gallbladder and other/unspecified parts of biliary tract.

CNS, central nervous system.

Table 2 ranks cancer incidence and mortality by sex in 2005. In males, the five leading primary sites of cancer were the stomach (CR 69.7, ASR 65.5), lung (CR 50.5, ASR 50.2), liver (CR 46.1, ASR 42.0), colon & rectum (CR 42.0, ASR 39.6), and prostate (CR 14.3, ASR 14.7), accounting for about 70% of all newly diagnosed cancers. In females, the most common cancer sites were the thyroid (CR 44.8, ASR 35.0), breast (CR 40.5, ASR 31.0), stomach (CR 36.2, ASR 26.3), colon & rectum (CR 30.4, ASR 22.2), lung (CR 19.0, ASR 13.2), and cervix uteri (CR 15.4, ASR 11.5), accounting for about 69% of all newly diagnosed cancers.

From the construction of a KNCI DB for 1999 onward to 2005, the completeness of the Korea cancer registry data has improved gradually. This might have contributed in part to the gradual overall increases in cancer incidence, especially among the elderly. Nonetheless, the increases in thyroid, colorectal and breast cancers in women and prostate cancer in men are notable.

Mortality

In 2005, 65,117 cancer deaths were reported in Korea, accounting for about 26.7% of all deaths (Table 3). The CRs of all sites combined were 168.5 and 98.8 per 100,000 for men and women, respectively, and the ASRs of all sites combined were 166.6 and 68.8 per 100,000 (Table 4). Cancers of the lung, stomach, liver and colon & rectum were the most common fatal cancers, which accounted for 64% of all cancer deaths.

Table 3

Ten leading causes of death during 2005 in Korea

*Age-standardized to the WHO world standard population.

Source: Mortality Data, 2006, Korea National Statistical Office.

Table 4

Crude and age-standardized cancer mortality rates by sex during 2005 in Korea

*Age-standardized to the WHO world standard population; †Includes gallbladder and other/unspecified parts of biliary tract.

CNS, central nervous system.

In men, the five leading primary cancer sites for mortality were the lung (CR 41.4, ASR 41.7), liver (CR 33.5, ASR 31.1), stomach (CR 29.3, ASR 28.9), colon & rectum (CR 13.4, ASR 13.5), and pancreas (CR 7.6, ASR 7.6). In women, the most common cancer sites for mortality were the stomach (CR 15.6, ASR 10.5), lung (CR 15.0, ASR 10.0), colon & rectum (CR 11.3, ASR 7.5), liver (CR 11.1, ASR 7.9), and gallbladder (CR 6.7, ASR 4.5).

Trends in cancer incidence

Tables 5.1-5.3 show the trends in cancer incidence for all sites combined and for selected cancer sites. The incidence rate for all sites combined increased by 2.5% annually from 1999 to 2005. The incidence rate for all sites combined increased by 1.2% annually in men and by 4.1% in women from 1999 to 2005.

Table 5-1

Trends in cancer incidence rates in both sexes during 1999-2005 in Korea

*annual percent change using age-standardized incidence based on the WHO world standard population; †Includes gallbladder and other/unspecified parts of biliary tract; ‡The APC is significantly different from zero (P<0.05).

CNS, central nervous system.

Table 5-3

Trends in cancer incidence rates in females during 1999-2005 in Korea

*annual percent change using age-standardized incidence based on the WHO world standard population; †Includes gallbladder and other/unspecified parts of biliary tract; ‡The APC is significantly different from zero (P<0.05).

CNS, central nervous system.

The incidence rates have continued to increase for colorectal and thyroid cancer in both sexes, along with breast cancer in females and prostate cancer in males. Stomach and lung cancer incidence rates plateaued in men and women, while the incidences of liver cancer in both sexes and the cervix in women have decreased.

One notable aspect is the sharp increase (25.1% annually) in the incidence of female thyroid cancer. As diagnostic techniques for thyroid cancer have become more sensitive, such as with the advent of ultrasound and fine-needle aspiration, the detection of subclinical disease has become possible. Therefore, the increased incidence of thyroid cancer might reflect improved diagnostic techniques for previously undetected disease, rather than a true increase in the occurrence of thyroid cancer (11, 12).

Trends in cancer mortality

Figs. 1&2 show the trends in cancer deaths for all sites combined and for selected cancer sites. Age-standardized mortality rates have decreased for all sites combined in both sexes since 2002.

Fig. 1

Annual age-standardized cancer incidence and death rates for all sites by sex during 1983-2005 in Korea.

Fig. 2

Annual age-standardized cancer mortality for selected cancers by sex during 1983-2005 in Korea.

For lung cancer, the leading site for cancer deaths since 1999, mortality has decreased slightly for men since 2001, but increased significantly in women. The age-standardized mortality rates of stomach and cervix uteri cancer have decreased continuously. Along with the significant increases in colorectal, prostate and female breast cancer incidence, the mortality rates of these cancers have also continued to increase.

Age-specific incidence rates for selected cancer sites

Table 6 presents the most common cancer sites by sex and age group. For ages 0-14 yr, leukemia was the most common form in both sexes. For males, stomach cancer was the most common in 15-64-yr-olds, while lung cancer was more frequent for those 65 and over. For females, the most common sites of cancer were the thyroid, breast and stomach for the 15-34-yr-old, 35-64-yr-old, and the 65 and over age groups, respectively. Fig. 3 shows the age-specific incidence rates of the selected cancers for men and women. The data show that the incidence of stomach, lung, liver and colorectal cancers increased gradually with age. In women, the age-specific incidence rates of breast and thyroid cancer has increased with age until the forties and decreased thereafter.

Table 6

Five major sites of cancer incidence by age group and sex during 2005 in Korea

*Includes gallbladder and other/unspecified parts of biliary tract.

CNS, central nervous system.

Fig. 3

Age-specific incidence rates of major cancers during 2005 in Korea.

Survival rates

Table 7 shows the 5-yr relative survivals for three periods: 1993-1995, 1996-2000, and 2001-2005. Notable improvement has been made in the 5-yr relative survival rates for all sites combined. The survival of females appears to have a better prognosis than that of males. This is partly explained by the high frequency of female cancers (e.g., thyroid, breast and uterine cervix) known to have relatively good prognoses.

Table 7

Trends in the 5-yr relative survival rates (%) by year of diagnosis during 1993-2005 in Korea

*Change in the 5-yr relative survival between 1993-1995 and 2001-2005 as a percentage; †Includes gallbladder and other/unspecified parts of biliary tract.

CNS, central nervous system.

The 5-yr relative survival rates appeared to be higher for most major cancer sites in patients diagnosed during 2001-2005 compared to 1993-1995, except for cancers of the pancreas, brain and central nervous system. The greatest improvements were seen in leukemia, non-Hodgkin's lymphoma, and prostate, stomach, colorectal and breast cancers.

The improving survival rates could be attributable to early detection, as well as to improved treatments (13, 14), but this needs to be evaluated further. Lack of progress in early detection and treatment could explain the observed absence of improvement in the survival rate of pancreatic cancer (15).

Table 5-2

Trends in cancer incidence rates in males during 1999-2005 in Korea

*annual percent change using age-standardized incidence based on the WHO world standard population; †Includes gallbladder and other/unspecified parts of biliary tract; ‡The APC is significantly different from zero (P<0.05).

CNS, central nervous system.