Globally, esophageal cancer is the 11th most common cancer, with 511,054 new cases, and the seventh leading cause of cancer-related mortality, resulting in 445,391 fatalities in 2022 [1]. In both sexes, the prevalence of esophageal cancer is highest in East Asia, followed by Southern Africa, East Africa, and Northern Europe. Given the geographic and regional differences in the clinical epidemiology of esophageal cancer, data from GLOBOCAN, a project of the International Agency for Research on Cancer, may not accurately represent the situation in Korea [2]. This study aimed to incorporate the latest statistics into the data from a previous study [3], in order to reflect the current status and recent changes in the epidemiology and treatment of esophageal cancer in Korea.

The Korea National Cancer Incidence Database (KNCI DB) served as a comprehensive nationwide registry documenting cancer occurrences. It included information on individuals diagnosed with cancer across more than 200 medical facilities in Korea, integrating data from both the central and 11 regional cancer registries [4]. Since 2000, the Korea Central Cancer Registry (KCCR) has taken over the functions previously managed by the KNCI DB.

The findings of the KCCR annual report on cancer incidence and cancer-related deaths in 2021 are shown in Fig. 1. The number of newly diagnosed cancer cases reached 277,523, marking a 10.8% increase from the previous year and setting a record high as medical services recovered from the impact of coronavirus disease 2019 (COVID-19). This upward trend is also evident in esophageal cancer, among many other cancer types. The number of newly diagnosed esophageal cancer patients has been increasing annually since 2000, although there was a decrease in 2020. This suggests that healthcare utilization diminished during the COVID-19 pandemic and began to rebound in 2021 [4,5].

Figure 1. Cancer incidence (A) and deaths (B) in Korea, 2021.

Esophageal cancer represented 1.0% (n=2,954) of all cancer cases, ranking as the 18th most common cancer. It was also the 10th leading cause of cancer-related deaths (n=1,569). The mortality-incidence ratio, which compares the number of deaths from a specific cause to its incidence, provides insights into the severity or lethality of a disease. In 2021, the mortality-incidence ratio for all cancers was 30.1, while for esophageal cancer, it was significantly higher at 53.1 in the total population. Esophageal cancer ranked fifth in terms of mortality in the total population, highlighting its high mortality rate and the importance of early-stage detection [4]. The incidence and 5-year relative survival rates for all cancers have steadily increased, with the relative survival rate reaching as high as 72.1% and a reported prevalence of 2.43 million. The total number of all cancer-related deaths was 82,688, with an age-standardized rate (ASR) of 161.1 per 100,000. For esophageal cancer, the crude incidence rate per 100,000 person-years was 5.8 (10.2 in men and 1.3 in women), and the ASR per 100,000 person-years was 5.5 (10.7 in men and 1.2 in women). In 2020, the standard population used for calculating the ASR was updated due to changes in Korea’s population structures; thus, the ASRs were reported relative to previously published statistics. From 1999 to 2021, the ASR for incidence per 100,000 person-years showed a significant decrease (APC 1.8% in both sexes) (Fig. 2).

Figure 2. Comparison of data between 1999 and 2021. Trends in the age-standardized incidence rate (A) and cancer mortality rate (B) per 100,000 person-years are shown. APC, annual percentage change.

This phenomenon is also evident in regional comparisons. An analysis of the ASRs for incidence per 100,000 person-years over 5-year intervals from 1999 to 2021 shows a decline in ASRs across all regions. Despite the increase in the number of newly diagnosed esophageal cancer patients, this suggests a decrease in the overall incidence rate. The ASRs for incidence per 100,000 person-years were calculated using the mid-year regional population of 2020 in Korea (Fig. 3).

Figure 3. Comparison of data from 1999 to 2021. Trends in the age-standardized incidence rate per 100,000 person-years across regions.

The ratio of men to women was 7.7:1. Esophageal cancer was most frequently diagnosed in patients in their 60s (38.2%) and 70s (29.1%) [4]. This trend has been maintained since 1999, except for the period from 2012 to 2015. During these years, the highest incidence was in patients in their 70s, followed by those in their 60s [6].

In 2021, the most common pathological type of esophageal cancer was squamous cell carcinoma, accounting for 91.3% of cases, followed by adenocarcinoma at 2.4%. When comparing the pathological type data from 1999 to 2021, the incidence of squamous cell carcinoma increased from 75.6% to 91.3%. Conversely, adenocarcinoma decreased from 3.4% to 2.4%, and unspecified carcinoma dropped from 18.3% to 3.7%. Excluding cases with unspecified histology, squamous cell carcinoma made up 92.5% of cases in 1999 [6]. This trend may reflect advancements in diagnostic techniques, allowing for more precise histopathological diagnoses than previously possible.

According to GLOBOCAN 2022, the ASR for esophageal cancer incidence per 100,000 people in Eastern Asia was 12.2 for men and 3.4 for women, with the highest prevalence rate observed in this region compared to others worldwide [7]. The esophageal cancer belt stretches from northern Iran through Central Asia to Mongolia and north-central China, where approximately 90% of esophageal cancer cases are predominantly squamous cell carcinoma. In contrast, adenocarcinoma is primarily found in Western countries [8]. Within Eastern Asia, the ASRs by Segi’s world population for incidence in China, Japan, and Korea were 8.3, 4.8, and 2.2, respectively, and for cancer-related deaths, they were 6.7, 2.6, and 1.2, respectively [9]. Despite having lower ASRs for both incidence and mortality of esophageal cancer compared to other countries in Eastern Asia, the specific reasons for these lower rates in Korea remain unclear.

The KCCR DB categorizes staging data as localized, regional, distant, or unknown, based on the extent of metastasis from the primary site, following the classification system of the Surveillance Epidemiology and End Results (SEER) program of the United States National Cancer Institute. The prevalence of localized and regional cancers was higher than that of distant and unknown cancers (Fig. 4). In Korea, the proportion of early-stage cancers has risen compared to findings from our previous study [3], and the 5-year relative survival rate for esophageal cancer has steadily increased from 14% (1993–1995) to 42% (2016–2020) in both sexes (Fig. 5). According to the SEER staging system, the 5-year relative survival rate for esophageal cancer has generally shown improvement since 2007 (Fig. 6).

Figure 4. Incidence rates of esophageal cancer per 100,000 person-years according to the Surveillance, Epidemiology, and End Results staging system.

Figure 5. Trends in the 5-year relative survival rate (%) in Korea from 1993 to 2020.

Figure 6. The 5-year relative survival rate (%) of patients with esophageal cancer from the time of diagnosis, according to the Surveillance, Epidemiology, and End Results staging system from 2007 to 2021.

Medical care for all Korean citizens is reimbursed by the National Health Insurance System, and every medical procedure is assessed by its subsidiary, the Health Insurance Review and Assessment Service (HIRA). HIRA released 5 medical quality evaluation reports in 2007, 2009, 2011, 2012, and 2014, over a span of 7 years. The comparison between high-volume centers and low-volume centers in treatment evaluation is shown in Table 1. Between 2007 (data from 2005 to 2006) and 2014 (data from 2012 to 2013), the number of esophagectomy cases increased from 1,272 across 76 centers to 1,751 across 82 centers (for 2 years), and the reported in-hospital mortality rate increased from 3.38% to 4.68%. According to the HIRA analysis, the minimum requirement for acceptable mortality was 21 esophagectomy procedures per 2 years, which was used as the cutoff value to define high-volume centers. Among all the institutions that offered esophagectomy, the high-volume centers accounted for 17.1% (13 centers) in 2005–2006 and 19.5% (16 centers) in 2012–2013, and performed 68.3% and 73.7%, respectively, of all esophagectomy procedures. Moreover, compared with low-volume hospitals, high-volume centers had better postoperative outcomes, based on lower operative mortality rates, shorter in-hospital stays, and lower in-hospital costs, in each evaluation year. The operative mortality rate at high-volume centers was 2.07% in 2005–2006 and 3.26% in 2012–2013, while it was 6.2% and 3.26% at low-volume centers in 2005–2006 and 2012–2013, respectively. The length of hospital stay at high-volume centers was 26.3 days in 2005–2006 and 25.68 days in 2012–2013. In low-volume centers, it was 30.55 days and 37.97 days, respectively. Moreover, high-volume centers incurred relatively low treatment costs and were predominantly located in the Seoul metropolitan area. These data indicated that high-volume centers had a positive impact on the outcomes of esophagectomy for esophageal cancer in Korea.

Table 1 . Health Insurance Review and Assessment Service treatment evaluation and comparison in a span of 2 years, comparing between high-volume and low-volume centers.

	No. of hospitals that performed esophagectomies			No. of esophagectomies performed			In-hospital mortality (%)			Length of hospital stay (day)
	Total	Over 21 cases		Total	Over 21 cases		Less than 21 cases	Over 21 cases		Less than 21 cases	Over 21 cases
2005–2006	76	13		1,272	869		6.20	2.07		30.55	26.30
2007–2008	76	13		1,386	940		8.74	2.87		30.90	23.33
2009–2010	75	18		1,506	1,188		15.41	3.11		42.50	26.88
2010–2011	73	15		1,625	1,185		9.55	3.80		38.40	26.34
2012–2013	82	16		1,751	1,290		8.68	3.26		37.97	25.68

Values are presented as number, %, or days..

The data obtained from the HIRA provided insights into the status of esophagectomy procedures in Korea. However, there have been no further reports from the HIRA since 2014, with the last report published a decade ago. Additionally, the HIRA only accounted for the number of operations reimbursed by the National Health Insurance System, excluding non-covered procedures such as robotic esophagectomy. Given the rise in robotic esophagectomy and early-stage esophageal cancer cases since 2014, the annual number and mortality rates of esophagectomy are likely outdated. Currently, Korea lacks accurate statistics and a dedicated registry or database for esophagectomy cases. Therefore, it is crucial to initiate additional efforts to establish a comprehensive nationwide registry or database for these procedures.

Esophageal cancer was the 18th most prevalent cancer and the 10th leading cause of cancer-related mortality in Korea in 2021, with its prevalence showing a gradual decline. This decrease in prevalence was also observed in regional comparisons spanning from 1999 to 2021. Esophageal cancer is most commonly diagnosed in individuals in their 60s and 70s. In 2021, there was a peak in cancer prevalence for diagnoses made within the last year, likely due to decreased healthcare utilization during the COVID-19 pandemic, followed by a recovery starting in 2021. The predominant type of esophageal cancer is squamous cell carcinoma, which increased from 75.6% in 1999 to 91.3% in 2021, while the incidence of adenocarcinoma decreased from 3.4% to 2.4%. These trends may reflect improvements in diagnostic accuracy over time. Compared to other Asian countries, Korea has lower incidence rates and cancer-related mortality rates, along with an improved 5-year relative survival rate for esophageal cancer. Localized and regional cancers showed a higher prevalence than distant and unknown cancers, with early-stage cancers in Korea showing an increase compared to previous studies. The 5-year relative survival rate for esophageal cancer has significantly increased from 14% (1993–1995) to 42% (2016–2020) and has generally improved since 2007 according to the SEER staging system. According to HIRA data, the number of esophageal cancer surgeries saw an increase in 2012–2013 compared to the initial survey period in 2005–2006. While in-hospital mortality rates increased, operative mortality, length of hospital stay, and in-hospital costs decreased, indicating advancements in the treatment of esophageal cancer over time. Given the prevalence and mortality rates of esophageal cancer, early diagnosis and proactive surgical treatment are believed to enhance survival rates. Establishing a nationwide database on esophageal cancer and esophagectomy is essential to accurately assess the current demographic statistics and treatment outcomes, which will help improve the survival rate of esophageal cancer in the future.

Authors contributions

Conceptualization: HWK, SYP. Data curation: HWK. Formal analysis: HWK, SYP. Investigation: HWK, SYP. Methodology: HWK, SYP. Writing–original draft: HWK. Writing–review & editing: HWK, SYP. Approval of final manuscript: SYP.

Conflict of interest

Seong Yong Park is an Editor-in-Chief of the Journal of Chest Surgery but was not involved in the peer reviewer selection, evaluation, or decision process of this article. Except for that, no other potential conflict of interest relevant to this article was reported.

Funding

This work was supported by a National Research Foundation of Korea grant from the Korean government (Ministry of Science and ICT) (No., 2022R1A2C209310611).