In Asian countries, breast densities and the proportion of younger women with breast cancer are higher than those in Western countries. This study was designed to determine differences in stage at diagnosis of breast cancer among Korean women according to screening history. The study population was derived from the Korea National Cancer Screening Program (KNCSP). The study cohort comprised 17,689 women who were newly diagnosed with breast cancer in 2011 and were invited to undergo breast cancer screening via the KNCSP between 2002 and 2011. Ductal carcinoma in situ (DCIS) and localized breast cancer were most frequent in both ever-screened and never-screened patients. Late stage cancer was significantly more frequent in never-screened patients, compared with ever-screened patients. Compared to never-screened women, the odds ratio (OR) for being diagnosed with early stage breast cancer among screened women was 1.41 (95% Confidence Interval [CI] = 1.28–1.55). The OR for being diagnosed with early stage breast cancer was highest among patients who underwent screening three times or more (aOR = 1.89, 95% CI = 1.57–2.29). Screening by mammography was associated with diagnosis of early stage breast cancer in Korean women. However, significant increases in the diagnosis of DCIS and localized breast cancers among ever-screened patients suggest the possibility of overdiagnosis due to screening.

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Purpose Fecal tests remain a mainstay of population-based colorectal cancer (CRC) screening programs worldwide. However, data on interval CRC (iCRC) arising after follow-up colonoscopy of a positive fecal test are scarce. We conducted a nationwide population-based study to reveal the risk and characteristics of iCRC in this setting.Materials and Methods We searched the National Cancer Screening Program for CRC database in Korea (2005-2010). Incidence of iCRC within the program was estimated, then Cox proportional-hazards regression analysis was performed to determine the independent predictors of iCRC. The clinical characteristics of iCRC were compared with screen-detected CRC (sCRC).Results We identified 280 iCRC among 150,660 negative colonoscopies as a follow-up exam to a positive fecal immunochemical test (FIT), and 2,427 sCRC. The overall incidence of iCRC was 0.49/1,000 person-years (95% confidence interval [CI], 0.48 to 0.51). iCRC was more likely to occur in men (adjusted hazard ratio [aHR], 1.79; 95% CI, 1.39 to 2.30) and elderly patients (aHR, 1.77; 95% CI, 1.38 to 2.28 in 65-74 years; aHR, 3.13, 95% CI, 2.13 to 4.60 in ≥ 75 years). The National Quality Improvement Program for colonoscopy reduced a short-term risk of iCRC (aHR, 0.48; 95% CI, 0.27 to 0.87). Compared with sCRC, iCRC was more likely to occur in the proximal colon, be diagnosed at the localized stage, and have a lower CRC mortality (32.7 vs. 17.4%, 56.8 vs. 34.1%, and 12.5 vs. 17.7%, respectively; all p < 0.05).Conclusion In a population-based CRC screening program with FIT, the burden of iCRC after follow-up colonoscopy was substantial. Men and elderly patients possess a significantly higher risk of iCRC.

Colorectal cancer has a high worldwide incidence. Japan, a country that is geographically and culturally similar to the Republic of Korea (here after Korea), has recently reported a decreasing trend in the incidence of colorectal cancer. However, Korea had the highest incidence of colorectal cancer among Asian countries in 2012. Our aim was to observe the changing trends in incidence and mortality of colorectal cancer in Korea and to compare them to those in Japan. Incidence data were collected from the Korean Central Cancer Registry and mortality data were collected from Korean Statistical Information Service. Incidence and mortality data on colorectal cancer in Japan were acquired from the National Cancer Center in Japan. Age-standardized incidence and mortality rates were determined based on Segi’s world population. Screening data from both countries were collected from the national cancer center in each country. In Korea, the age-standardized incidence rate of colorectal cancer in both sexes was 20.9 to 38.0 per 100,000 from 1999 to 2012 and the rate in males increased more dramatically than in females. In addition, the increase between 2002 and 2012 was first observed in the age group over 40. In Japan, the incidence of colorectal cancer has been more constant over recent years than in Korea. The age-standardized mortality rate of colorectal cancer in both sexes in Korea was 8.5 to 9.3 per 100,000 from 2000 to 2013, and the trend in mortality was constant during this period. In Japan, the mortality rate decreased slightly during the same period. Crude screening rates were increased overall in both Korea and Japan during the period studied. Since the incidence of colorectal cancer has increased in Korea, the control of this cancer is an important public health issue. As Japan has achieved a reduction in colorectal cancer, adjustment of Korea’s current systems for screening and treatment of colorectal cancer according to those of Japan may contribute to improved colorectal cancer control in Korea.

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