Association of Socioeconomic Disparities With Nasopharyngeal Carcinoma Survival in an Endemic Area,China

Abstract

Objectives

This retrospective cohort study investigated the association of socioeconomic status with survival outcomes among patients with nasopharyngeal carcinoma in an endemic area of China.

Methods

The primary endpoint was overall survival. Survival outcomes were estimated by the Kaplan-Meier method and compared by the log-rank test, and the multivariate Cox proportional hazards model was used to estimate hazard ratios, 95% CIs, and independent prognostic factors.

Results

A total of 11 069 adult patients with NPC were enrolled and included in the analysis. Kaplan-Meier survival analysis revealed that overall survival was significantly different among socioeconomic status. Compared with high socioeconomic status patients, low socioeconomic status patients (HR, 1.190; 95% CI, 1.063-1.333) and medium socioeconomic status patients (HR, 1.111; 95% CI, 1.006-1.226) were associated with increased hazard ratio (HR) of overall survival.

Conclusion

This analysis highlights patients with nasopharyngeal carcinoma who had high socioeconomic status had better overall survival compared with those who had low and medium socioeconomic status.

Introduction

Despite improvements over the past several decades in cancer survival, marked socioeconomic disparities persist. As a risk factor for cancer survival, socioeconomic disparities have been identified as a challenge for public health worldwide.^1,2 Socioeconomic disparities could negatively impact cancer diagnosis and survival through their effects on geographical distribution, educational levels, disposable income, and access to affordable health care services. ² In the United States, the 5-year survival rate for patients who were diagnosed with cancer was 71% for the high household income group (≥$75,000) and 57% for the low household income group (≤$35,000). ³ A similar pattern was observed in geographical distribution. Patients living in more populated metropolitan areas had a greater 5-year survival rate than those residing in nonmetropolitan areas (69% vs 62%). ³ Generally, cancer survival is favorable for patients of higher socioeconomic status (SES). ⁴ Nasopharyngeal carcinoma (NPC) is endemic to southern China, Southeast Asia, and Africa, with age-standardized incidence rates of 4-25 per 100 000 population in these regions, which are approximately 50-100 times higher than the incidence rates in the rest of the world. ⁵ However, few studies have focused on the association between SES and survival outcomes for nasopharyngeal carcinoma patients. ⁶ In this large, register-based cohort study, we assessed the influence of socioeconomic disparities on the survival outcomes of patients with NPC in an endemic area.

Materials and Methods

Data Collection and Study Design

In this retrospective cohort study, data were derived from 1 hospital-based cancer registry in Guangzhou (Sun Yat-sen University Cancer Center), Guangdong Province. NPC patients in the Cancer Registration System of Sun Yat-sen University Cancer Center were enrolled between January 1, 2000, and December 31, 2013. The Cancer Registration System records detailed information on demographic and socioeconomic characteristics, diagnosis, clinical staging, Karnofsky Performance Score (KPS), treatment modality, long-term follow-up, and clinical endpoints. Flexible fiberoptic nasopharyngoscopy or magnetic resonance imaging of the nasopharyngeal and whole neck areas were assessed at baseline. Imaging examinations were performed every 3 months for 3 years, and then every 6 months until death. This study was reviewed and approved by the Clinical Research Ethics Committee of Sun Yat-sen University Cancer Center (SYSUCC) (GZR2018-097), and informed consent forms were signed by all patients. This study followed the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) reporting guidelines.

An SES model was built by using a principal component analysis of several SES indicator variables.^7,8 SES was categorized into 3 groups (low, medium, and high) according to China’s fourth economic census SES indicator variables ⁹ : geographic distribution (urban, rural), educational level (low, less than primary education; medium, secondary education; high, tertiary education), and disposable income (<$2,000, $2000-$6,000, and >$6000).

Statistical Analyses

For baseline characteristics, χ² tests were used to measure differences between SES for categorical variables, and continuous variables were analyzed using analysis of variance. The primary endpoint was overall survival (OS), which was defined as the time from diagnosis to death from any cause. OS was calculated by using the Kaplan-Meier method, and we used the log-rank test to compare differences between SES in survival. A multivariable Cox proportional hazards model was used to calculate HRs and 95% CIs and identify independent factors associated with the prognosis of NPC patients. All tests were 2-sided, and P < .05 was considered significant. All analyses were performed using SPSS, version 28 (SPSS Inc., Chicago).

Results

In the cohort, 11 069 adult patients with NPC were included in the analysis; 8309 (75.07%) were men, 2760 (24.93%) were women, and the mean (SD) age was 45.98 (11.4) years. With regard to SES, 2607 patients (23.55%) had a low SES, 5751 patients (51.96%) had a medium SES, and 2711 patients (24.49%) had a high SES. The patient characteristics are presented in Supplementary Table 1. High-SES patients tended to live in urban regions and have higher educational and disposable income levels. Additionally, compared with low- and medium-SES patients, high-SES patients were more likely to have favorable baseline characteristics. The median follow-up time for the whole cohort was 5.52 years (.1-15.64 years). Kaplan-Meier survival analysis revealed that OS was significantly different among SES levels, with a 5-year survival rate of 82.39% among low-SES patients, 83.93% among medium-SES patients, and 87.13% among high-SES patients (Figure 1; P < .001). In a multivariable model, all patient and tumor demographic variables, including sex, age, smoking status, T classification, N classification, clinical stage, KPS, histology, and SES, were identified as covariates, and SES was a significant independent factor. Compared with high-SES patients, low-SES patients (HR, 1.190; 95% CI, 1.063-1.333) and medium-SES patients (HR, 1.111; 95% CI, 1.006-1.226) had an increased hazard ratio (HR) of overall survival (Supplementary Table 2).

Figure 1.

Kaplan-Meier Curves for Overall Survival in NPC patients stratified by socioeconomic status (SES).

Discussion

China has established a basic health insurance system and improved people’s access to essential health care, leading to declines in overall cancer mortality. ¹⁰ However, many people with lower SES have not benefitted equitably from those health systems. The country still faces many challenges, such as unequally distributed health services, high medical costs, and inadequate investment in medical insurance. ¹¹ Our previous study of data from 1002 adult patients who were diagnosed with NPC between 2010 and 2014 identified that, compared with rural patients, patients residing in urban regions had a better prognosis (HR, 3.126; 95% CI, 1.902-5.138). ¹² Patients with NPC living in rural areas are less likely to receive sufficient health care services, as recommended by the guidelines for treatment. Similarly, patients living in rural areas are more likely to receive treatment at low-quality hospitals. The extensive use of innovative medicine and advanced medical technologies might increase the financial burden and exacerbate more disparities in receiving guideline-concordant treatment, such as effective interventions that ensure access to health care, including enrollment in clinical trials and receiving funding from charitable organizations.

The health system ensures that many individuals with cancer have access to cancer screening and treatment, although the insurance premium increases continuously every year, coinciding with the original goals of the system. ¹³ It is critical to strengthen the affordability of high-quality medical insurance coverage for individuals with cancer. China should continue to reform its health system to provide more equal, effective, and low-cost health care for its 1.4 billion citizens. Policy change is needed for the National Health Commission of the People’s Republic of China, Chinese Center for Disease Control and Prevention, other national agencies, and provincial and local agencies to expand health insurance coverage, improve access to cancer treatment, and increase diversity in nursing care. Effective interventions by health policy-makers and health care providers could substantially eliminate cancer disparities.

Strengths and Limitations

The principal strengths of our study are that it used an SES model to assess socioeconomic disparities while providing quantifiable measures that combined SES indicator variables. Additionally, this study included comprehensive patient characteristics as well as prognostic outcomes.

The main limitation of our study is its retrospective and single hospital-based design, and further studies are needed to validate our results. Moreover, treatment modality is highly associated with SES, and we lacked a treatment modality variable to account for socioeconomic disparities in cancer survival. Therefore, a national register-based cohort study is necessary to validate our results and seek far-reaching interventions for health equity.

Conclusion

Our study revealed that SES was associated with the outcomes of patients with NPC. Patients with NPC who had a high SES had better overall survival than those who had a low and medium SES. This finding highlights the disparities in access to health care for NPC patients in an endemic area in China.

Supplemental Material

Supplemental Material - Association of Socioeconomic Disparities With Nasopharyngeal Carcinoma Survival in an Endemic Area, China

Supplemental Material for Association of Socioeconomic Disparities With Nasopharyngeal Carcinoma Survival in an Endemic Area, China by Dong-Fang Meng, Hai-Bo Zhang, Guo-Ying Liu, Li-Xia Peng, Qi Yang, Zi-Hao Liu, Raru Tian, Ji Ma, and Lei Fu in Cancer Control.

Data Availability Statement

The datasets are not available for public access due to patient privacy concerns but are available from the corresponding author on reasonable request.