In South Korea, the NHI provides mandatory universal health insurance and offers comprehensive medical care coverage to all South Korean residents. Study data were obtained from 2002 to 2013 from the NHI Sharing Service provided by the NHI Corporation. These data were claims data from 1,000,000 people, representing 2% of the entire Korean population, randomly selected after the entire population was stratified according to sociodemographic parameters (age, sex, and income). The database includes detailed patient sociodemographic information, such as sex, age, health insurance premiums, residential area, comorbid diseases, treatment information including disease diagnoses, imaging and laboratory tests, procedures, and death outcomes. Patients with code C34 claims, indicating lung cancer according to the International Classification of Diseases, 10th edition, Clinical Modification (ICD-10-CM), were screened. Among 7,489 patients having code C34 from 2002 to 2013, only lung cancer patients newly diagnosed after 2003 were included, so that the confounding effects due to pre-diagnosed lung cancer could be minimized. Early stage lung cancer can be billed as benign neoplasm at the time of surgery. Therefore, patients who were continuously billed as lung cancer (C34) after surgery were included in the study. Given that illegal billing practices such as upcoding occur in the healthcare industry, patients were also excluded if they only had a diagnosis of lung cancer, without histories of treatment and hospital admission (n=2,586). Patients with code C34 in 2002 (n=344) and those younger than 30 (n=21) were also excluded. Thus, a total of 4,538 patients with newly diagnosed lung cancer constituted the study population (Fig. 1).

We analyzed treatment patterns and medical costs in terms of the primary treatment modality, whether surgery (OP), radiation therapy (RTx), or chemotherapy (CTx). OP included open/thoracoscopic resection of the trachea or lungs, as well as mediastinal lymph node dissection (MLND) (Korean National Health Insurance [KNHI] reimbursement codes O1311-O1316, O1341-O1345, O1401-O1432, and O1596). The OP type was categorized as pneumonectomy, lobectomy, segmentectomy, wedge resection, and MLND only. The exploratory thoracotomy (KNHI reimbursement codes ‘O1360’) was not included. RTx encompassed all types of radiotherapy, including conformal and intensity-modulated RTx. Although patients may have undergone additional therapy before or after OP and RTx, they were categorized in terms of their primary treatment modality. CTx regimens used for lung cancer were applied in this study. The cost of each treatment modality was also calculated. “No treatment” was operationally defined as hospitalization with lung cancer (C34) without any treatment.

Patient sociodemographic parameters included age, income class, and residential area. Patients were divided into five categories according to their age at diagnosis (< 49, 50-59, 60-69, 70-79, and ≥ 80 years). Income class was divided into quartiles as provided by the KNHI. Residential area was divided into three categories (metropolitan, urban, and suburban/rural) based on population density. Descriptive statistics were used to characterize treatment patterns and medical costs according to sociodemographic factors. The annual p for trend was determined with a Wilcoxon type test for trend across ordered groups. All tests were two-tailed, with p < 0.05 considered significant. Statistical analyses were performed with Stata/SE software ver. 12.1 (Stata Corp., College Station, TX).

The informed consent was waived and the study protocol was approved by the Institutional Review Board of Chungbuk National University (2015-04-005).

The mean age was 67.1 years (standard deviation, 11.6), and 46% of the patients were over the age of 70. Moreover, more than 10% of subjects were over the age of 80. Males constituted the majority, about 70% of the study population. Detailed characteristics of the study population were in Table 1. Suburban/rural areas were the most common regions of residence. Whereas income levels were generally evenly distributed, the fourth quartile contained the highest percentage of subjects (31%). “No treatment” (“No Tx”) was the most common primary treatment regimen, and “CTx only” was the next most common primary treatment regimen. Nineteen percent of subjects received OP as the primary treatment, while 26.7% received RTx and 43.9% received CTx.

The overall mean medical costs by sex, age, income, and residence are shown in Fig. 2A-D. The medical costs attributed to patients under the age of 60 were slightly higher than those attributed to other age groups (Fig. 2B), although the former made up only around 25% of the lung cancer cases during the 10-year study period (Fig. 3B). Similar trends were observed in residential areas and medical costs. The majority of lung cancer subjects came from suburban/rural areas (Fig. 3D), but the medical costs attributed to these subjects were markedly lower than those attributed to subjects from metropolitan or urban areas (Fig. 2D).

The distributions of primary treatment regimens according to various factors are shown in Fig. 2E-H. As expected, a markedly higher proportion of younger subjects received OP, and “no treatment” highly increased with age. Notably, the proportion of subjects who received no treatment was much lower in metropolitan areas.

There was a statistically significant trend of change in the gender distribution of lung cancer cases (p for trend=0.003), in which the proportion of females increased over the years (Fig. 3A). The age distribution also displayed a significant trend of change over time (p for trend < 0.001), as the proportions of subjects aged 70-79 and ≥ 80 increased, while the proportion of subjects aged 30-49 decreased (Fig. 3B). The overall proportion of lowest-income or highest-income group slightly increased over the years (p for trend=0.004) (Fig. 3C). The residential area of lung cancer patients had a slight fluctuation over the years (p for trend=0.041) (Fig. 3D).

There was an overall increase in the proportion of subjects who received OP as the primary treatment (p for trend < 0.001), whereas there was no overall significant change for RTx (p for trend=0.066) or CTx (p for trend=0.057) (Fig. 4A). There was a statistically significant trend of change in the primary treatment regimen over the years (overall p for trend < 0.001), where notably the proportion of subjects who received no treatment decreased, and the proportion of subjects who received only OP increased (Fig. 4B). There was not a statistically significant trend of change in the type of surgery (p for trend=0.090); nonetheless, the proportion of subjects who received pneumonectomy decreased, while the proportion of subjects who received lobectomy increased (Fig. 4C).

There was an overall statistically significant trend of change in the mean total medical cost for lung cancer treatment (p for trend < 0.001), notably for OP and RTx. The proportion of medical costs from CTx decreased (Fig. 5).