This study presents the 2014 nationwide cancer statistics in Korea, including cancer incidence, survival, prevalence, and mortality.
Materials and Methods
Cancer incidence data from 1999 to 2014 was obtained from the Korea National Cancer Incidence Database and followed until December 31, 2015. Mortality data from 1983 to 2014 were obtained from Statistics Korea. The prevalence was defined as the number of cancer patients alive on January 1, 2015, among all cancer patients diagnosed since 1999. Crude and age-standardized rates (ASRs) for incidence, mortality, prevalence, and 5-year relative survivals were also calculated.
In 2014, 217,057 and 76,611 Koreans were newly diagnosed and died from cancer respectively. The ASRs for cancer incidence and mortality in 2014 were 270.7 and 85.1 per 100,000, respectively. The all-cancer incidence rate has increased significantly by 3.4% annually from 1999 to 2012, and started to decrease after 2012 (2012-2014; annual percent change, –6.6%). However, overall cancer mortality has decreased 2.7% annually since 2002. The 5-year relative survival rate for patients diagnosed with cancer between 2010 and 2014 was 70.3%, an improvement from the 41.2% for patients diagnosed between 1993 and 1995.
Age-standardized cancer incidence rates have decreased since 2012 and mortality rates have also declined since 2002, while 5-year survival rates have improved remarkably from 1993-1995 to 2010-2014 in Korea.
Cancer is a major life-threatening disease worldwide. Approximately 14.1 million patients were newly diagnosed with cancer and 8.2 million people died from cancer in 2012 worldwide . The global burden of cancer is expected to grow rapidly due to aging population .
In Korea, cancer accounts for one in four deaths and more than 200,000 new cancer cases were diagnosed in 2013 .The number of cancer incidences and deaths are expected to increase with an aging population and westernized lifestyles . Additionally, the economic burden of cancer in Korea increased approximately 1.8-fold, from $11,424 to $20,858 million, between 2000 and 2010 .
In this context, cancer statistics are the most important indicator to assess the national cancer burden and form cancer prevention and control strategies. This article aims to provide nationwide cancer statistics including incidence, survival, prevalence, and mortality in 2014.
Materials and Methods
1. Data sources
The Korea Central Cancer Registry (KCCR) was established by the Ministry of Health and Welfare in 1980 as a nationwide hospital-based cancer registry. Since 1999, the KCCR has collected cancer incidence data nationwide by integrating a hospital-based KCCR database with data from regional cancer registry programs. The KCCR currently provides the nationwide cancer incidence, survival, and prevalence statistics annually .
The KCCR built the Korea National Cancer Incidence Database (KNCI DB) from hospitals, 11 population-based registries, and additional medical chart reviews. The KNCI DB contains information regarding age, sex, region, date of diagnosis, primary cancer site, histological type, most valid diagnostic method, and SEER stage. The completeness of cancer incidence data for 2014 was estimated to be 97.8% based on the method proposed by Ajiki et al. . The mid-year population and cancer mortality data from 1983 to 2014 were obtained from Statistics Korea . To ascertain vital status and to calculate survival and prevalence, the KNCI DB was linked to mortality data and population registration data from Ministry of the Interior.
All incidence cases were registered according to the International Classification of Diseases for Oncology, 3rd edition  and converted to the International Classification of Diseases, 10th edition (ICD-10) . The mortality cases were registered according to ICD-10. All cancer cases were reported based on the 24 cancer types.
3. Statistical analyses
Rates were expressed as crude and age-standardized rates (CR and ASR, respectively) per 100,000 individuals. The crude rate was calculated as the total number of incidence/ mortality cases divided by the mid-year population of the specified years. The ASR is a weighted average of the age-specific rates, where the weights are the proportions of persons in the corresponding age groups of a standard population . In this report, ASRs were calculated using Segi’s world standard population . The cumulative risk of developing cancer from birth to life expectancy was calculated using cumulative rates; that is, the sum of the age-specific rates from birth to life expectancy, as follows .
Trends in incidence/mortality rates were summarized as an annual percentage change (APC) by using a Joinpoint regression. APC is the average percentage change of rates and is calculated as follows :
, where log(Ry)=b0+b1y,
log(Ry) is the natural log transformed age standardized rates.
The survival duration for each cancer case was determined as the interval between the date of initial diagnosis and the date of death, date of loss of follow-up, or closing date for follow-up. The 5-year relative survival rates were calculated as the ratios of the observed survival of the cancer patients to the expected survival of the general population, which was derived from the standard life table provided by Statistics Korea. Trends in 5-year relative survival rates were evaluated as percentage differences in 5-year relative survival rates from 1993-1995 and 2010-2014. Relative survival rates were calculated using the Ederer II method  with some minor corrections, based on an algorithm by Paul Dickman .
Prevalent cases were defined as the number of cancer patients alive on January 1, 2015 among all cancer patients diagnosed between 1999 and 2014. Limited-duration prevalences were calculated using SEER*Stat software. Any p-values less than 0.05 were considered statistically significant. SEER*Stat 8.2.1 (National Cancer Institute, Bethesda, MD), Joinpoint 4. 1. 1 (National Cancer Institute), and SAS 9.3 (SAS Institute, Cary, NC) were used in this report.
A total of 217,057 cases were newly diagnosed with cancer during the study period (Table 1). Of these cases, 112,882 (52.0%) were men and 104,175 (48.0%) were women. Thyroid cancer was the most commonly diagnosed cancer in 2014, followed by stomach, colorectal, lung, and breast cancer in 2014. The overall cumulative risk of developing cancer from birth to life expectancy was 36.2%. However, the cumulative risk of developing cancer from birth to life expectancy was higher in men (38.7%) than in women (33.1%) (data not shown).
The total CR and ASR for overall cancer incidences in 2014 were 427.6 and 270.7 per 100,000, respectively (Table 2). According to sex, CRs for all sites combined were 444.9 per 100,000 in men and 410.3 per 100,000 in women. The ASRs were 302.2 and 255.5 per 100,000 in men and women, respectively. Stomach cancer (CR, 79.2 per 100,000) was the most common cancer in men, followed by lung (CR, 66.0 per 100,000), colorectal (CR, 63.8 per 100,000), liver (CR, 47.5 per 100,000), and prostate cancer (CR, 38.6 per 100,000). These five cancers accounted for 66.3% of newly diagnosed cases in men during the study period. In contrast, thyroid cancer (CR, 97.0 per 100,000) was the most common cancer among women, followed by breast (CR, 72.1 per 100,000), colorectal (CR, 42.5 per 100,000), stomach (CR, 38.5 per 100,000), and lung cancer (CR, 28.7 per 100,000). These five cancers accounted for 67.9% of cases in women.
In 2014, the total number of deaths from cancer was 76,611, accounting for 28.6% of all deaths (Table 3). Expressed based on sex, 62.5% and 37.5% of cancer deaths occurred in men and women, respectively (Table 1).
The total CR and ASR for cancer deaths were 150.9 and 85.1 per 100,000, respectively, in 2014 (Table 4). The total CR and ASR for cancer deaths per 100,000 were higher among men (CR, 188.7; ASR, 125.8) than in women (CR, 113.2; ASR, 55.6).
According to the cancer sites, lung cancer (CR, 50.4 per 100,000) was the leading cause of death in men, followed by liver (CR, 34.0 per 100,000), stomach (CR, 22.7 per 100,000), colorectal (CR, 18.8 per 100,000), and pancreatic cancer (CR, 10.8 per 100,000). The top five causes of deaths from cancer in women included lung (CR, 18.3 per 100,000), colorectal (CR, 14.1 per 100,000), stomach (CR, 12.4 per 100,000), liver (CR, 11.6 per 100,000), and pancreatic cancer (CR, 9.3 per 100,000).
3. Trends in cancer incidence and mortality
Fig. 1 shows trends in cancer incidence and mortality from 1983 to 2014. The ASR for all-cancer incidence increased by 3.4% annually from 1999 to 2012, and then began to decrease from 2012 to 2014 (APC, –6.6%) (Table 5, Fig. 1). Cancers in stomach, colorectum, lung and thyroid started to decrease around 2011 (Table 5, Fig. 2). Especially, ASR for thyroid cancer has increased rapidly 22.4% from 1999 to 2011, but then decreased swiftly 10.8% annually starting in 2011. Incidence of breast cancer has increased constantly throughout the period, but APC was slowed from 2005. Conversely, the incidence rates of cervix and liver showed constant decrease for the whole period. The incidence rate for liver cancer has started to decrease since 1999. After 2011, decreasing rate for liver cancer was more steepen.
The ASR for all-cancer mortality rate has been increased until 2002 (Table 6, Fig. 1). After that year, it began to decrease (2002-2014; APC, –2.7%). Same patterns were shown in men and women. Most cancer sites, including lung, liver, colorectum, gallbladder, leukemia, brain and central nervous system, cervix uteri, and thyroid started to decrease in the early 2000s. However, cancers in stomach, larynx, testis, bladder, and non-Hodgkin lymphoma decreased starting in 1999 (Table 6, Fig. 3). Cancers in the pancreas, breast, and prostate showed constant increasing trends for the whole period.
4. Age-specific incidence rates
Leukemia was the most commonly diagnosed cancer among children between 0 and 14 years of age. Thyroid cancer was the most common cancer among adolescents and young adults between 15 and 34 years of age (Table 7). For men, the incidence rate of cancer increased until age 70 (Fig. 4A). Stomach cancer was the most commonly diagnosed cancer among men 35 to 64 years old, while lung cancer was the most common among men 65 and over. In contrast, thyroid cancer was most commonly diagnosed among women 35 to 64 years old, while colorectal cancer was the most common among women 65 and older. Thyroid and breast cancer showed an inverted U-shaped incidence rates by age (Fig. 4B).
5. Survival rates
The 5-year relative survival rates for all cancer combined improved remarkably in both sexes, from 41.2% in 1993-1995 to 70.3% in 2010-2014 (Table 8, Fig. 5A). After excluding thyroid cancer, the 5-year relative survival rates for all cancer still increased from 1993 to 2014 (Fig. 5B).
The 5-year relative survival rate during 2010-2014 for all cancer combined was 62.2% in men and 78.2% in women, respectively. The 5-year relative survival rate for thyroid cancer was over 100%, while the 5-year relative survival rates for testis, prostate, and breast cancer were over 90% in 2010-2014 for both sexes, respectively. However, the 5-year relative survival rate for pancreatic cancer was only 10.1% in both sexes in 2010-2014.
When compared to the 5-year relative survival rate for men in 1993-1995, prostate cancer diagnosed from 2010 to 2014 showed the most outstanding improvement, followed by stomach cancer, leukemia, lip/oral cavity/pharynx and liver cancer. Among women, stomach cancer diagnosed during 2010-2014 showed the greatest improvement in 5-year relative survival rates compared to those between 1993 and1995, followed by leukemia, non-Hodgkin lymphoma, colorectal, and liver cancer.
6. Prevalence rates
A total of 1,464,935 cancer prevalent cases were identified on January 1, 2015 (Table 1). Of these cases, 645,332 (44.1%) were men and 819,603 (55.9%) were women. The crude and age-standardized prevalence rates for cancer overall were 2,885.8 per 100,000 individuals and 1,837.6 per 100,000 individuals for both sexes, respectively, in 2014 (Table 9).
The five most common cancers for men were stomach (CR, 615.8 per 100,000), colorectal (CR, 477.1 per 100,000), prostate (CR, 245.3 per 100,000), thyroid (CR, 215.6 per 100,000), and liver cancer (CR, 170.2 per 100,000). In contrast, thyroid cancer was most common in women (CR, 1,076.8 per 100,000), followed by breast (CR, 623.5 per 100,000), colorectal (CR, 320.0 per 100,000), stomach (CR, 310.8 per 100,000), and cervix uteri cancer (CR, 178.0 per 100,000).
Analysis of the period after cancer diagnosis revealed that thyroid (20.1%) cancer was the most prevalent cancer within two years after diagnosis, followed by stomach (14.1%) and colorectal cancer (13.1%) (Fig. 6). Thyroid cancer (27.2%) was most prevalent for 2-5 years, followed by stomach (14.8%) and colorectal cancer (13.9%). After 5 years, thyroid cancer (20.4%) was the most prevalent cancer, followed by stomach (18.0%) and colorectal cancer (14.1%).
Conflict of interest relevant to this article was not reported.
This work was supported by a research grant from the National Cancer Center (No. 1610200), Republic of Korea. The authors are indebted to the Korea Central Cancer Registry (KCCR)-affiliated hospitals, non-KCCR-affiliated hospitals, the National Health Insurance Service and Statistics Korea for data collection.