To estimate the current cancer burden in Korea, cancer incidence and mortality rates were projected for the year 2013.
Materials and Methods
Cancer incidence data from 1999 to 2010 were obtained from the Korea National Cancer Incidence Database, and cancer mortality data from 1993 to 2011 were obtained from Statistics Korea. Cancer incidence in 2013 was projected by fitting a linear regression model to observed age-specific cancer incidence rates against observed years, then multiplying the projected age-specific rates by the age-specific population. For cancer mortality, a similar procedure was used, except that a Joinpoint regression model was used to determine at which year the linear trend changed significantly.
In total, 247,732 new cancer cases and 74,179 cancer deaths are projected to occur in Korea in 2013. For all sites combined, the crude incidence rates are projected to be 489.8 and 492.2, and the age-standardized incidences to be 350.4 and 318.4 per 100,000 for males and females, respectively.
Since 1983, as the leading cause of death , cancer has become a major public health concern in Korea. Annually, over 200,000 patients are newly diagnosed with cancer in Korea, and one in four deaths is due to cancer [2,3]. Although the cancer registration system in Korea is very efficient and can provide nationwide cancer statistics within a relatively short time, an at least 2-year lag for accurate data collection and compilation is necessary. To plan and apply a cancer control program, it is important to assess the number of new cases and deaths that are expected to occur during the current year. In this report, we provide the projected cancer incidence and mortality rate based on data up to 2010.
Materials and Methods
The Korean Ministry of Health and Welfare initiated a nationwide, hospital-based cancer registry (the Korea Central Cancer Registry [KCCR]) in 1980. The details of the history, objectives, and activities of the KCCR have been documented elsewhere . Incidence data from 1999 to 2010 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  and converted according to the International Classification of Diseases, 10th edition (ICD-10) .
Mortality data from 1993 to 2011 were obtained from Statistics Korea . The cause of death was coded and classified according to ICD-10.
The cancer sites included in this report are 1) all cancers combined and 2) the 24 most common cancers: lip, oral cavity, and pharynx (C00-C14), esophagus (C15), stomach (C16), colon and rectum (C18-C20), liver and intrahepatic bile duct (liver) (C22), gallbladder and other parts of the biliary tract (gallbladder) (C23-C24), pancreas (C25), larynx (C32), lung and bronchus (lung) (C33-C34), breast (C50), cervix uteri (C53), corpus uteri (C54), ovary (C56), prostate (C61), testis (C62), kidney (C64), bladder (C67), brain and central nervous system (C70-C72), thyroid (C73), Hodgkin lymphoma (C81), non-Hodgkin lymphoma (C82-C85, C96), multiple myeloma (C90), leukemia (C91-C95), and all others.
Population data were obtained from the resident registration population, reported by Statistics Korea. The mid-year population, on July 1 of the respective year, was used when computing the incidence and deaths.
Due to the time required for data collection and analysis, incidence and mortality data are available usually 2-3 years behind the current year. Thus, we projected the expected number of new cancer cases and deaths in Korea in the current year to provide an estimate of the current cancer burden.
Linear regression models  were used to assess time trends and the projection of rates. Based on the observed cancer incidence data, a linear regression model was fitted to the age-specific rates by 5-year age group against observed years. From the projected age-specific rates in 2013, the estimated number of cancer cases was calculated by multiplying the rates by the projected 2013 age-specific population size. For thyroid and prostate cancer, which showed significant curvilinear trends, we used a square-root transformation when fitting a linear regression model and converted the predicted values back to the original scale.
To estimate the number of cancer deaths in 2013, we first ran a Joinpoint regression model on the data for 1993-2011 to detect the year of significant changes in the trends in cancer mortality by sex and cancer site. A Joinpoint regression describes changes in data trends by connecting several different line segments on a log scale at "joinpoints." This analysis was performed using the Joinpoint software (ver. 4.0; http://surveillance.cancer.gov/joinpoint) from the Surveillance Research Program of the US National Cancer Institute . After identifying the year of significant trend changes using Joinpoint regression analysis, a simple linear regression model was fitted to the last line segment to estimate age-specific cancer mortality rates in 2013. Similar to the method used for the projection of cancer incidence, the number of new deaths was then projected by multiplying the age-specific cancer mortality rates by 2013's projected age-specific population.
We summarized the results using crude rates (CRs) and age-standardized rates (ASRs) of cancer incidence and mortality. The ASRs were standardized using the world standard population .
Table 1 presents the estimated number of new cancer cases and deaths during 2013 in Korea by sex and cancer site. It is projected that 247,732 cancer incidence cases will occur in 2013.
Table 2 presents the estimated CRs and ASRs of cancer incidence in 2013 by sex and cancer site. The CRs of all sites combined in males and females in 2013 are projected to be 489.8 and 492.2, respectively, per 100,000, and the ASRs of all sites combined are projected to be 350.4 and 318.4, respectively, per 100,000. In males, the five leading primary sites of cancer are expected to be the stomach (CR, 89.1; ASR, 62.6), colon and rectum (CR, 82.2; ASR, 58.1), lung (CR, 65.3; ASR, 46.1), liver (CR, 49.4; ASR, 34.4), and prostate (CR, 48.3; ASR, 34.5), accounting for 68.2% of all newly diagnosed cancers in 2013. In females, the five leading primary sites are expected to be thyroid (CR, 174.4; ASR, 124.1), breast (CR, 67.6; ASR, 45.8), colon and rectum (CR, 51.7; ASR, 29.8), stomach (CR, 42.1; ASR, 24.6), and lung (CR, 28.0; ASR, 15.0), accounting for 73.9% of all newly diagnosed cancers (Fig. 1). Thyroid cancer alone is projected to account for 35.4% (43,973 cases) of incident cases in females in 2013.
Table 3 presents the most common cancer sites expected in 2013 by sex and age group. Leukemia and thyroid cancer are projected to be the most common forms of cancer in both sexes for the 0-14 and 15-34 age groups. Gastric cancer is predicted to be the most common cancer in males 35-64 years of age, while lung cancer is predicted to be more frequent in males≥65 years of age. Thyroid cancer is predicted to be the most common cancer in females 35-64 years of age, whereas colorectal cancer is predicted to be the most common cancer in females≥65 years of age. Fig. 2 shows the age-specific incidence rates of the selected cancers for males and females in 2013. The projection indicates that the incidences of gastric, lung, liver, and colorectal cancers will increase gradually with age. In women, the age-specific incidence rates of breast and thyroid cancer will increase with age until 50 years of age, and then level off.
It is estimated that 74,179 cancer deaths will occur in Korea during 2013 (Table 1, Fig. 2). The CRs of all sites combined in 2013 for males and females are projected to be 184.7 and 109.3, respectively, per 100,000, and the ASRs of all sites combined are expected to be 131.8 and 56.3, respectively, per 100,000 (Table 4).
In 2013, the five leading cancer sites causing mortality in males are predicted to be lung (CR, 47.4; ASR, 33.4), liver (CR, 31.7; ASR, 22.3), colon and rectum (CR, 22.3; ASR 16.0), stomach (CR, 21.2; ASR, 15.1), and pancreas (CR, 10.8; ASR, 7.7). During the same time period, in females, lung cancer (CR, 17.8; ASR, 8.6) is projected to be the leading cancer site causing mortality, followed by cancers of the colon and rectum (CR, 14.3; ASR, 7.0), stomach (CR, 11.7; ASR, 5.7), liver (CR, 10.8; ASR, 5.6), and pancreas (CR, 9.1; ASR, 4.5).
Fig. 3 shows the age-specific predicted mortality rates of the selected cancers for males and females in 2013. When examined by age, Korean males≥60 years of age are expected to have the highest mortality rates from lung cancer. In contrast, Korean females≥55 years of age are expected to have the highest mortality rates from breast cancer, followed by lung cancer.
This report provides estimated nationwide cancer incidence and mortality in Korea for the current year. In total, 247,732 new cancer cases and 74,179 cancer deaths are expected in Korea during 2013. In Korean males, gastric, colorectal, lung, liver, and prostate cancers are estimated to have the highest incidences, while lung, liver, colorectal, gastric, and pancreatic cancers are estimated to be the most common causes of cancer-related deaths. In Korean females, thyroid, breast, colorectal, gastric, and lung cancer are estimated to have the highest incidences, while lung, colorectal, gastric, liver, and pancreatic cancers are estimated to be the most common causes of cancer-related deaths.
Cancer has become an important public health concern in Korea, and as the population continues to age, the cancer burden will continue to increase. The estimated cancer statistics for the current year given in this report represent an important resource for planning and evaluating cancer-control programs. The estimates in this report, however, are projected numbers based on statistical models and may vary from year to year; hence, these estimates should be used with caution.
This work was supported by a research grant from the National Cancer Center (No. 1310220), Republic of Korea.
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