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ARTICLE: STOMACH

Disparities in the Diagnosis and Treatment of Gastric Cancer in Relation to Disabilities

Kim, Hyoung Woo MD1; Shin, Dong Wook MD, DrPH, MBA2,3; Yeob, Kyoung Eun MPH, PhD4; Cho, In Young MD2; Kim, So Young MD, PhD4–6; Park, Seon Mee MD, PhD1; Park, Jong Heon MD, PhD7; Park, Jong Hyock MD, MPH, PhD4,6; Kawachi, Ichiro MD, PhD6

Author Information
Clinical and Translational Gastroenterology: October 2020 - Volume 11 - Issue 10 - p e00242
doi: 10.14309/ctg.0000000000000242

Abstract

INTRODUCTION

As of 2018, gastric cancer (GC) is the sixth most common cancer worldwide (1) and is the third leading cause of death from cancer worldwide (1). Although its global incidence is declining, in 2015, it was still the most common cancer in men, and the fourth most common cancer in women in Korea with an age-standardized incidence rate of 49.3 in men and 20.5 in women per 100,000 (2).

Although the overall prognosis of GC worldwide is still poor (1), it has been improving with earlier detection and advances in treatment. In Korea, GC screening is provided to all people older than 40 years as part of the National Cancer Screening Program (3,4), and the effectiveness of this program was estimated to be a 21% reduction in GC mortality. In addition, improvements have been made in GC treatment, including surgery (5–10) and chemotherapy (11,12). As a result, the age-standardized GC mortality rate declined from 23.8 to 8.9 per 100,000 persons from 1999 to 2015 (2).

People with disabilities represent the largest group of vulnerable populations, and the average prevalence rate in the adult population aged 18 years and older is 15.6% according to the World Health Survey (13). In Korea, even with a narrow definition of disability, the prevalence rate was about 5.4% in 2017 (http://kosis.kr). People with disabilities have physical, communication, psychosocial, and practical barriers to health care access and utilization (14–19). In addition, they often have lower education and income levels (20–23). Thus, they may be diagnosed at a later stage of disease or have an unknown disease status, receive inappropriate or no standard treatment, and have worse survival (24–27).

Therefore, it is important to identify the potential disparities of the cancer diagnosis and treatment between patients with disabilities and those without (24–27). In the United States, a previous study using the Surveillance, Epidemiology, and End Results–Medicare/Social Security Disability Insurance (SSDI) databases examined the potential disparities in the cancer diagnosis and treatment (26). For example, in colorectal cancer, there were no significant diagnostic disparities between people with and without Medicare/SSDI, but people with Medicare/SSDI had higher cancer-specific mortality compared with control (26). However, this study was limited because of restricted assessment of disability depending on Medicare/SSDI status (e.g., people with disabilities who are employed cannot apply for Medicare/SSDI), inclusion of only 5 conditions (mental, neurologic, circulatory, respiratory, and musculoskeletal disorders and exclusion of visual and hearing disabilities), and lack of data on disability severity. Furthermore, only those younger than 65 years were included, limiting the generalizability of results. Probably because of the lower GC incidence in developed countries, there are few studies on the disparities in GC diagnosis and treatment in relation to disabilities.

The Korean is covered by a single-payer, universal health insurance system. The copayment for diagnostic tests and treatment for cancer is capped to 5%, and those in the lowest income bracket are covered by a medical aid program. Furthermore, Korea has a well-established national cancer registry and national disability registration system, which provides an optimal setting for examining cancer care disparities among people with disabilities.

In this study, using the linked administrative database, we investigated potential disparities in the diagnosis, treatment, and survival of GC among people with and without disabilities.

METHODS

Study setting and data source

Korean National Health System.

The National Health Insurance Service (NHIS) provides obligatory public health insurance for 97% of all Koreans, and the insurance premium is calculated depending on income level. People who are unemployed and have the lowest assets (around 3% of the population) are covered by the Medical Aid program. Healthcare providers deliver medical care and are reimbursed generally through fee-for-service, and submission of healthcare data is required for reimbursement. Therefore, the NHIS has all the data required for reimbursement, which includes demographic data (including age, sex, area of residence, and income level), medical conditions (based on International Classification of Disease-10 codes), and information on the diagnostic tests and treatment procedures performed, along with a list of the prescriptions. The NHIS has also established a research database (National Health Insurance Research Database), which is available for research purposes. The National Health Insurance Research Database has been used in several epidemiologic and health policy studies (28,29), and further details can be found elsewhere (30,31).

Disability registration system in Korea.

A national registration system for people with disabilities was established in 1988, to determine the eligibility for welfare benefits based on disability type and severity. According to legislation, there are 15 categories of disability: brain, facial, visual, auditory, linguistic, heart, respiratory, liver, kidney, ostomy, limb, epilepsy, intellectual, autistic, and mental. A medical specialist evaluated functional losses and clinical impairments that persisted longer than 6 months, and the severity of disability was classified into 6 levels according to government criteria (32). Furthermore, after the initial assessment, they are subject to reassessment and reclassification after 2–3 years, and if their disability seems to be permanent at that time, they are exempt from further reassessment. However, as initial registration requires that functional losses and clinical impairments persist longer than 6 months, most people with disabilities registered in the disability registration system maintain their status. In our study, the types of disabilities were rearranged in to 5 groups: (i) physical (brain impairment and limb disability), (ii) communication (visual, auditory, and linguistic disability), (iii) mental (intellectual, autistic, and mental disability), (iv) internal organ (heart, lung, and renal disability plus ostomy), and (v) other (facial disfigurement and epilepsy). We then dichotomized severity levels into either severe (grades 1–3) or mild (grades 4–6).

Cancer registration system in Korea.

The Korean Central Cancer Registry is a government-sponsored, nationwide cancer registry, and includes data on age at diagnosis, sex, date of diagnosis, cancer site, and Surveillance, Epidemiology, and End Results stage.

Study subjects

First, we linked the Korean NHIS database with national disability registration data and selected 3 control subjects for each subject with any registered disability during 2009–2013 through age- and sex-matching. Second, cancer registration data from Korean Central Cancer Registry were linked to all subjects in the Korean NHIS-disability study data set.

The study population included all subjects who were diagnosed with GC (International Classification of Disease code C16) from January 1, 2009, to December 31, 2013 (n = 81,505). Control subjects were assigned an index date, corresponding to the date of the GC diagnosis of their matched GC patients. We excluded patients who (i) were younger than 19 years at diagnosis or index date (n = 1), (ii) had a history of other cancers before the GC diagnosis (n = 4,872), or (iii) had missing data (n = 911).

The final sample consisted of 75,721 patients with GC, of which 16,849 had a disability and 58,872 did not. Therefore, the case-to-control ratio was generally well-maintained (case:control = 1:3.49). Finally, we linked our data set to vital statistics provided by the Korean National Statistical Office, which include the date and cause of death (Figure 1).

Figure 1.
Figure 1.:
Study participants.

Institutional Review Board approval was obtained from Chungbuk National University (IRB No. CBNU-201708-BM-501-01).

Statistical analysis

The summary of statistics includes the presence or absence of disabilities, severity of the disabilities, and the 5 predefined disability categories. Cancer stage and treatment received were also tabulated by disability status, and statistical differences were tested by the χ2 test.

Cox regression analysis was used to determine the hazard ratios for the overall and GC-specific mortality for people with disabilities compared with control. Survival was calculated from the GC diagnosis or index date until the date of death, censor date (outmigration or death from other causes for GC-specific mortality), or last follow-up date (December 31, 2015). The multivariable model included age, sex, Charlson comorbidity index (33), income level, residential area, cancer stage, and treatment received. The same analyses were repeated with the surgery subset. All the analyses were performed using SAS statistical software (version 9.4; SAS Institute, Cary, NC). P values <0.05 were considered statistically significant.

RESULTS

Subject characteristics

GC patients with disabilities were slightly younger than the control subjects (66.0 vs 66.5 years), and those with mental and other impairments were much younger (56.0 and 58.9 years, respectively). They had more comorbidities and higher Charlson comorbidity index scores (1.5 vs 1.1). In addition, they were more likely to be living in rural areas and had lower income levels (Table 1).

Table 1.
Table 1.:
Characteristics of patients with gastric cancer

Disease status by disability characteristics

In general, people with disabilities had similar stage distributions compared to people without disabilities, except that they were slightly more likely to have an unknown disease status (8.4% vs 6.9%). However, the localized stage was lower in people with severe disabilities (53.7% for grades 1–3 and 46.8% for grade 1), whereas the unknown stage was more common (10.7% for grades 1–3 and 15.1% for grade 1). Among disability types, people with mental impairment tended to be diagnosed at a later disease status (localized stage 41.7%) and were more likely to have an unknown stage (15.2%) (Table 2).

Table 2.
Table 2.:
Stage at diagnosis in patients with and without disability

Treatment patterns by disability characteristics

People with disabilities were less likely to undergo surgery (65.1% vs 66.2%), perioperative chemotherapy (8.8% vs 9.5%), and palliative chemotherapy (5.6% vs 6.6%) and also tended to have no cancer treatment at all compare with the control subjects (29.3% vs 27.2%). This trend was more prominent in patients with severe disabilities than in those with mild disabilities (50.4% vs 58.3% in surgery alone, 8.3% vs 9.0% in surgery plus chemotherapy, 5.6% vs 5.6% in palliative chemotherapy, and 35.4% vs 26.6% in no treatment, respectively). By disability type, not receiving treatment was more common for communication impairment (36.9% in severe disability and 31.4% in mild disability) and mental impairment (32.3%) (Table 3 and see Supplementary Table 1, Supplementary Digital Content 1, http://links.lww.com/CTG/A395).

Table 3.
Table 3.:
Patterns of treatment according to the disability characteristics of patients with gastric cancer

Survival in all patients with GC

In total, 37.1% (28,071 of 75,721) of patients with GC died during an average follow-up of 3.4 years. People with disabilities had a slightly higher risk of mortality than those without disabilities (adjusted hazard ratio [aHR] = 1.18, 95% confidence interval [CI]: 1.14–1.21). Moreover, this difference was more prominent in the severe disability group (aHR = 1.62, 95% CI: 1.56–1.69), whereas overall mortality risk in the mild disability group was marginally higher than those in the control subjects (aHR = 1.05, 95% CI: 1.01–1.08). Likewise, by disability type, the risk of overall mortality was consistently higher in the severe disability group with physical impairment (aHR = 1.48, 95% CI: 1.40–1.56), communication impairment (aHR = 1.31, 95% CI: 1.21–1.43), mental impairment (aHR = 2.06, 95% CI: 1.82–2.34), internal organ impairment (aHR = 1.89, 95% CI: 1.70–2.10), and other impairment (aHR = 1.96, 95% CI: 1.11–3.46).

GC itself accounted for 76.9% of all deaths (21,595 of 28,071). GC-specific mortality risk showed a similar pattern to the overall mortality risk except for lower HR in people with internal organ impairment (Table 4).

Table 4.
Table 4.:
Overall and cancer-specific mortality risk of patients with gastric cancer of all stages

Treatment patterns and survival in patients with resected GC

Among patients who underwent surgical treatment, people with disabilities received adjuvant therapy at a similar rate to people without disabilities (13.0% vs 13.9%), including those with severe disabilities (13.5%). People with internal organ impairment were less likely to receive adjuvant therapy (6.1%) (see Supplementary Table 2, Supplementary Digital Content 1, http://links.lww.com/CTG/A395).

People with disabilities had a higher risk of overall mortality than those without disabilities (aHR = 1.21, 95% CI: 1.16–1.27). This difference was more marked in the severe disability group (aHR = 1.69, 95% CI: 1.57–1.81), but was not significant in the mild disability group (aHR = 1.05, 95% CI: 0.99–1.11). In the severe disability group, the risk was significantly higher across all disability types (aHR = 1.64 in physical impairment, aHR = 1.24 in communication impairment, aHR = 1.88 in mental impairment, aHR = 2.83 in internal organ impairment, and aHR = 3.53 in other impairments). The above-mentioned estimates were generally consistent with those for GC-specific mortality (Table 5).

Table 5.
Table 5.:
Risk of overall and cancer-specific mortality for patients with resected gastric cancer

DISCUSSION

This is the first study to undertake a comprehensive investigation into the potential disparity between GC care and disabilities. Our study showed that GC patients with disabilities, especially those with severe disability and mental impairment, are likely to be diagnosed at a later stage, receive less adequate treatment, and have worse clinical prognosis compared with patients free of disabilities. The particular strengths of our study include the large and representative samples covering the whole nation, assessment of a comprehensive range of disabling conditions, and objective assessment of the disability type and severity.

We found that people with severe disabilities and mental impairments tend to be diagnosed at a later stage. They face practical barriers to primary care utilization because of physical access and communication barriers (34), and they have been reported to undergoing cancer screening at lower rates compared to people without disabilities because of a lack of awareness of care recommendations and difficulty understanding the importance of screening (15–19). For example, significant disparities were found in GC, colorectal cancer, and cervical cancer screening, especially in patients with severe brain-related or mental disabilities in Korea and the United States (15–19). Therefore, we suspect that lower cancer screening rates as well as lower rates of primary care utilization might be associated with later diagnosis in people with severe disabilities and mental impairments.

We found that the stage of disease was more likely to be marked “unknown” among people with disabilities. Like a previous study on disparities in lung cancer (24), this trend was more evident in the severe disability group and among those with mental impairments. GC staging may be “unknown” because patients did not receive proper staging tests to establish an appropriate treatment plan, which means that they probably gave up subsequent treatment (35). However, disability itself is not a contraindication for receiving cancer treatment. These results may reflect the ableism inherent in patients, family members, or healthcare providers, which is an attitude that devalues or sets limitations on the capabilities of people with disabilities.

Our study showed that people with disabilities were more likely to receive no cancer treatment and were less likely to undergo surgery or chemotherapy, especially when their disability is severe. Our findings imply that people with disabilities may be discouraged from receiving cancer treatment by their healthcare providers or family members, who may undervalue the benefits of treatment and overemphasize complications in patients with disabilities (24,25,27). Furthermore, receiving less treatment was more evident in people with communication and mental impairments. These patients often have difficulty in communicating with healthcare providers and limited access to oncological information (23,24,36,37). In addition, decision-making capability may limit the patients with mental impairment of treating their own oncological problems (23,24,36). Therefore, it is necessary to develop medically specialized communication and decision aids to fit the needs and to optimize cancer treatment in patients with disabilities (38).

After adjustment for the patients' characteristics, disease status, and treatment, patients with disabilities had a higher overall and GC-specific mortality. As death from GC comprises most of the deaths (5,054/6,872, 73.5%) in our population, it generally reflects the excess risk of GC death, but other causes can also account for excess mortality, at least partly. Excess GC-specific death in patients with disabilities could be due to the real-life practice of offering less intensive treatment or poor compliance with treatment. Communication or cognitive abilities are important in making adequate decisions and in adherence to cancer treatment (23,24,36,37) and would explain the higher mortality in patients with communication or mental impairment. In addition, death from other causes would be higher in patients with disabilities because they have more comorbidities and poor socioeconomic conditions (24–27). This was evidenced by a higher risk of overall mortality (aHR = 1.89) compared with GC-specific mortality (aHR = 1.12). Potential strategies to reduce prognostic disparities may include the optimization of cancer treatment by overcoming the ableism of family members or healthcare providers and providing socioeconomic aid for people with GC and disabilities (24–27).

Similar to above, overall and GC-specific mortalities were slightly higher in people with resected GC and disabilities (aHR = 1.21) and more pronounced in those with severe disabilities (aHR = 1.68). Among patients with different disability types, people with mental impairment had higher GC-specific mortality (aHR = 1.83), although more of them received adjuvant chemotherapy, suggesting the possibility of less intensive surgery, incompletion of scheduled chemotherapy, or poorly controlled GC care, probably because of communication barriers with healthcare providers (39–42). People with severe physical impairment also had higher GC-specific mortality (aHR = 1.48), suggesting the possibility of less intensive oncologic treatment, probably because of higher risk of recurrent stroke or postoperative ileus (43,44). Therefore, to overcome the disparities in treatment outcomes, appropriate selection of the recipients of surgery and/or intensive adjuvant therapy and rigorous postoperative care may be required.

This study was a retrospective cohort design and had several limitations. First, unknown disease status accounted for 7.2% of all patients, and also, 27.7% of all patients did not receive oncological treatment. However, we do not know why these patients did not receive staging work-up or oncological treatment (e.g. patient or family refusal, clinical judgment by healthcare providers, or economic problems). Second, we did not have detailed clinical information on type of surgical procedure (e.g., laparoscopic or open resection), postoperative morbidity and mortality, pathologic results, adequacy of adjuvant or palliative treatment (e.g., chemotherapy dose, chemotherapy cycles, or number of radiotherapy), medication history such as proton pump inhibitor use, aspirin, or statin use, Helicobacter pylori status, or adherence to supportive care, which may have been helpful for interpreting disparities in treatment outcomes.

In conclusion, patients with GC and disabilities, especially severe disabilities, are diagnosed at a later stage, received less staging evaluation and treatment, and their overall survival rate was slightly worse than those without disabilities. This was more evident in people with mental impairment, although they generally do not have physical reasons to receive less screening, diagnostic work-up, and treatment. Although some degree of disparity might be due to rational clinical decisions, a large portion of the disparity seems to be unjustifiable. Efforts should be made to decrease the diagnostic, therapeutic, and prognostic disparities related to disabilities in GC care.

CONFLICTS OF INTEREST

Guarantor of the article: Jong Hyock Park, MD, MPH, PhD.

Specific author contributions: Hyoung Woo Kim, MD, and Dong Wook Shin, MD, DrPH, MBA, contributed equally to this work as first author. D.W.S. and J.H.P.: study design. K.E.Y., S.Y.K., and J.H.P.: investigation. S.Y.K. and J.H.P.: resources. H.W.K., D.W.S., J.H.P., and J.H.P.: analysis and interpretation. H.W.K. and D.W.S.: writing of manuscript. I.Y.C., S.M.P., J.H.P., and I.K.: review and editing. D.W.S., J.H.P., and I.K.: supervision.

Financial support: This work was supported by the R&D grant (No. 2016007) on rehabilitation by Korea National Rehabilitation Center Research Institute, Ministry of Health & Welfare, and the National Research Foundation of Korea (NRF) grant funded by the Ministry of Education (No. 2019R1H1A2080180, 2019R1A2C1087507).

Potential competing interests: None to report.

Study Highlights

WHAT IS KNOWN

  • ✓ People with disabilities have physical, communication, psychosocial, and practical barriers.
  • ✓ They represent a potentially vulnerable group with respect to access to healthcare system.

WHAT IS NEW HERE

  • ✓ People with disabilities were diagnosed with gastric cancer at a later stage.
  • ✓ They received less cancer staging evaluation and treatment and had a slightly higher mortality.

TRANSLATIONAL IMPACT

  • ✓ Diagnostic, therapeutic, and prognostic disparities were pronounced in people with severe disability and mental impairment.

REFERENCES

1. Bray F, Ferlay J, Soerjomataram I, et al. Global cancer statistics 2018: GLOBOCAN estimates of incidence and mortality worldwide for 36 cancers in 185 countries. CA Cancer J Clin 2018;68:394–424.
2. Jung KW, Won YJ, Kong HJ, et al. Cancer statistics in Korea: Incidence, mortality, survival, and prevalence in 2015. Cancer Res Treat 2018;50:303–16.
3. Lee S, Jun JK, Suh M, et al. Gastric cancer screening uptake trends in Korea: Results for the National Cancer Screening Program from 2002 to 2011: A prospective cross-sectional study. Medicine (Baltimore) 2015;94:e533.
4. Jun JK, Choi KS, Lee HY, et al. Effectiveness of the Korean National Cancer Screening Program in reducing gastric cancer mortality. Gastroenterology 2017;152:1319–28.e7.
5. Schwarz RE, Smith DD. Clinical impact of lymphadenectomy extent in resectable gastric cancer of advanced stage. Ann Surg Oncol 2007;14:317–28.
6. Songun I, Putter H, Kranenbarg EM, et al. Surgical treatment of gastric cancer: 15-year follow-up results of the randomised nationwide Dutch D1D2 trial. Lancet Oncol 2010;11:439–49.
7. Xiong JJ, Nunes QM, Huang W, et al. Laparoscopic vs open total gastrectomy for gastric cancer: A meta-analysis. World J Gastroenterol 2013;19:8114–32.
8. Zou ZH, Zhao LY, Mou TY, et al. Laparoscopic vs open D2 gastrectomy for locally advanced gastric cancer: A meta-analysis. World J Gastroenterol 2014;20:16750–64.
9. Japanese gastric cancer treatment guidelines 2014 (ver. 4). Gastric Cancer 2017;20:1–19.
10. Ono H, Kondo H, Gotoda T, et al. Endoscopic mucosal resection for treatment of early gastric cancer. Gut 2001;48:225–9.
11. Noh SH, Park SR, Yang HK, et al. Adjuvant capecitabine plus oxaliplatin for gastric cancer after D2 gastrectomy (CLASSIC): 5-year follow-up of an open-label, randomised phase 3 trial. Lancet Oncol 2014;15:1389–96.
12. Bang YJ, Van Cutsem E, Feyereislova A, et al. Trastuzumab in combination with chemotherapy versus chemotherapy alone for treatment of HER2-positive advanced gastric or gastro-oesophageal junction cancer (ToGA): A phase 3, open-label, randomised controlled trial. Lancet 2010;376:687–97.
13. WHO guidelines approved by the Guidelines Review Committee. In: World Report on Disability 2011. World Health Organization: Geneva, Switzerland, 2011.
14. Ramirez A, Farmer GC, Grant D, et al. Disability and preventive cancer screening: Results from the 2001 California Health Interview Survey. Am J Public Health 2005;95:2057–64.
15. Horner-Johnson W, Dobbertin K, Iezzoni LI. Disparities in receipt of breast and cervical cancer screening for rural women age 18 to 64 with disabilities. Womens Health Issues 2015;25:246–53.
16. Deroche CB, McDermott SW, Mann JR, et al. Colorectal cancer screening adherence in selected disabilities over 10 years. Am J Prev Med 2017;52:735–41.
17. Shin DW, Lee JW, Jung JH, et al. Disparities in cervical cancer screening among women with disabilities: A National Database Study in South Korea. J Clin Oncol 2018;36:2778–86.
18. Shin DW, Chang D, Jung JH, et al. Disparities in the participation rate of colorectal cancer screening by fecal occult blood test among people with disabilities: A National Database Study in South Korea. Cancer Res Treat 2020;52:60–73.
19. Kim Y, Shin DW, Kim HW, et al. Disparities in gastric cancer screening among people with disabilities: A national registry-linkage study in South Korea. Gastric Cancer 2020;23:497–509.
20. Kroll T, Jones GC, Kehn M, et al. Barriers and strategies affecting the utilisation of primary preventive services for people with physical disabilities: A qualitative inquiry. Health Soc Care Community 2006;14:284–93.
21. Diab ME, Johnston MV. Relationships between level of disability and receipt of preventive health services. Arch Phys Med Rehabil 2004;85:749–57.
22. Institute of Medicine Committee on Cancer Research Among Minorities and the Medically Underserved. The National Academies Collection: Reports funded by National Institutes of Health. In Haynes MA, Smedley BD (eds). The Unequal Burden of Cancer: An Assessment of NIH Research and Programs for Ethnic Minorities and the Medically Underserved. National Academies Press (US) National Academy of Sciences: Washington, DC, 1999.
23. Horner-Johnson W, Dobbertin K, Lee JC, et al. Disparities in health care access and receipt of preventive services by disability type: Analysis of the medical expenditure panel survey. Health Serv Res 2014;49:1980–99.
24. Shin DW, Cho JH, Noh JM, et al. Disparities in the diagnosis and treatment of lung cancer among people with disabilities. J Thorac Oncol 2019;14:163–75.
25. Kwon J, Kim SY, Yeob KE, et al. The effect of disability on the diagnosis and treatment of multiple myeloma in Korea: A National Cohort Study. Cancer Res Treat 2020;52:1–9.
26. McCarthy EP, Ngo LH, Chirikos TN, et al. Cancer stage at diagnosis and survival among persons with Social Security Disability Insurance on Medicare. Health Serv Res 2007;42:611–28.
27. McCarthy EP, Ngo LH, Roetzheim RG, et al. Disparities in breast cancer treatment and survival for women with disabilities. Ann Intern Med 2006;145:637–45.
28. Lee H, Cho J, Shin DW, et al. Association of cardiovascular health screening with mortality, clinical outcomes, and health care cost: A nationwide cohort study. Prev Med 2015;70:19–25.
29. Shin DW, Cho B, Guallar E. Korean National Health Insurance Database. JAMA Intern Med 2016;176:138.
30. Cheol Seong S, Kim YY, Khang YH, et al. Data resource profile: The National Health Information Database of the National Health Insurance Service in South Korea. Int J Epidemiol 2017;46:799–800.
31. Lee J, Lee JS, Park SH, et al. Cohort profile: The National Health Insurance Service-National Sample Cohort (NHIS-NSC), South Korea. Int J Epidemiol 2017;46:e15.
32. Jeon B, Kwon S, Kim H. Health care utilization by people with disabilities: A longitudinal analysis of the Korea Welfare Panel Study (KoWePS). Disabil Health J 2015;8:353–62.
33. Nuttall M, van der Meulen J, Emberton M. Charlson scores based on ICD-10 administrative data were valid in assessing comorbidity in patients undergoing urological cancer surgery. J Clin Epidemiol 2006;59:265–73.
34. Eun SJ, Hong JY, Lee JY, et al. Differences in medical care utilization rates of the disabled and the non-disabled with ambulatory care sensitive conditions [in Ko]. J Prev Med Public Health 2006;39:411–8.
35. Gurney J, Sarfati D, Stanley J, et al. Unstaged cancer in a population-based registry: Prevalence, predictors and patient prognosis. Cancer Epidemiol 2013;37:498–504.
36. Havercamp SM, Scandlin D, Roth M. Health disparities among adults with developmental disabilities, adults with other disabilities, and adults not reporting disability in North Carolina. Public Health Rep 2004;119:418–26.
37. Withers J, Speight C. Health care for individuals with hearing loss or vision loss: A minefield of barriers to accessibility. NC Med J 2017;78:107–12.
38. Bailey R, Willner P, Dymond S. A visual aid to decision-making for people with intellectual disabilities. Res Dev Disabil 2011;32:37–46.
39. Kim JH, Chin HM, Jun KH. Surgical outcomes and survival after gastrectomy in octogenarians with gastric cancer. J Surg Res 2015;198:80–6.
40. Valle JW, Palmer D, Jackson R, et al. Optimal duration and timing of adjuvant chemotherapy after definitive surgery for ductal adenocarcinoma of the pancreas: Ongoing lessons from the ESPAC-3 study. J Clin Oncol 2014;32:504–12.
41. Di Bartolomeo M, Pietrantonio F, Rulli E, et al. Impact on survival of timing and duration of adjuvant chemotherapy in radically resected gastric cancer. Tumori 2016;102:e15–9.
42. Jiang N, Deng JY, Ding XW, et al. Effect of complication grade on survival following curative gastrectomy for carcinoma. World J Gastroenterol 2014;20:8244–52.
43. Kuan AS, Chen SC, Yeh CM, et al. Risk of ischemic stroke in patients with gastric cancer: A nationwide population-based cohort study. Medicine (Baltimore) 2015;94:e1336.
44. Li QG, Li P, Tang D, et al. Impact of postoperative complications on long-term survival after radical resection for gastric cancer. World J Gastroenterol 2013;19:4060–5.

Supplemental Digital Content

© 2020 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of The American College of Gastroenterology