Purpose: This study used the Surveillance, Epidemiology, and End Results (SEER) data to investigate the changes in incidence, treatment, and survival of lung cancer from 1973 to 2015.
Patients and methods: The clinical and epidemiological data of patients with lung cancer were obtained from the SEER database. Joinpoint regression models were used to estimate the rate changes in lung cancer related to incidence, treatment, and survival.
Results: From 1973 to 2015, the average incidence of lung cancer was 59.0/100,000 personyears. The incidence increased initially, reached a peak in 1992, and then gradually decreased. A higher incidence rate was observed in males than in females and in black patients than in other racial groups. Since 1985, adenocarcinoma became the most prevalent histopathological type.
The surgical rate for lung cancer was about 25%, and treatment with chemotherapy showed an increasing trend, while the radiotherapy rate was in downward trend. The surgical rate for non-small-cell lung cancer (NSCLC) was higher than that for small cell lung cancer (SCLC), while chemotherapy for SCLC far exceeded that for NSCLC. Treatment with chemotherapy and
radiotherapy for advanced stage had higher rate than early stage. The 5-year relative survival rate of lung cancer increased with time, but <21%.
Conclusion: In the past four decades, the lung cancer incidence increased initially and then gradually decreased. Surgical rate experienced a fluctuant reduction, while the chemotherapy rate was in upward trend. The 5-year relative survival rate increased with years, but was still low.
Keywords: lung cancer, incidence, treatment, survival, SEER database
Lung cancer is the leading cause of cancer death and is attributed to more than 25% of all cancer deaths. In the United States, it is estimated that ~225,000 patients are diagnosed with lung cancer with 160,000 deaths due to lung cancer annually.1 However, it has been reported that the incidence of lung cancer has significantly declined among men and women in all racial groups in recent decades.2,3
Primary lung cancer is typically divided into two main histopathological types: small cell lung cancer (SCLC) and non-small-cell lung cancer (NSCLC). NSCLC accounts for 85% of lung cancer cases, including three main subtypes, namely adenocarcinoma (ADC), squamous cell carcinoma (SCC), and large cell carcinoma (LCC).4 The trends in lung cancer incidence rates by histopathological types have shifted over the past few decades in the United States.5–8 Polednak9 found that the incidence rates of ADC, SCC, and SCLC decreased from 1992 to 2005 in the United States. This decline in incidence was also observed for LCC in another study.10 During this period, the incidence of SCC was observed to decrease more rapidly than that of ADC. At present, ADC is more common than SCC in the United States.5,6
Lung cancer is one of the most aggressive malignant tumors, especially SCLC. The treatments for lung cancer mainly include surgical resection and chemotherapy. In general, patients with early-stage lung cancer usually undergo surgery, while patients with advanced or metastatic disease are treated with chemotherapy.11 However, treatment methods have also shifted over the decades. Despite improved treatment, lung cancer still has a poor prognosis and the 5-year survival rate remains at a very low level.12 Several factors, such as age, sex, lung function, clinical and pathological stage, body constitution, comorbidity, and optimal treatment, influence the survival of lung cancer patients.13
To our knowledge, there have been some publications on an international level to access the trend in some aspects of lung cancer,14,15 but no studies on the changes in incidence, treatment, and long-term survival rate of lung cancer spanning four decades have been carried out. In this study, we used the population-based Surveillance, Epidemiology and End Results (SEER) database, which represents 26% of the US population, to investigate changes in the incidence, treatment, and 5-year relative survival rate of lung cancer analyzed by sex, age, race, and histopathological type over time.
MATERIALS AND METHODS
The SEER database is an open access resource for cancer-based epidemiology and survival analyses. The SEER program includes 18 cancer registries collecting information on newly diagnosed cases within SEER geographic regions in the United States, and covers ~97% of all incident cancers in its registry areas. More than 8 million cancer cases spanning four decades are registered in this database.
The data on patients with lung cancer were obtained from the SEER database via SEER*Stat, version 8.3.5 (http://seer.cancer.gov/seerstat/). We defined lung cancer using the ICD for Oncology, Version 3 (ICD-O-3). Patients with labeled primary sites, C34.1-upper lobe, lung, C34.2-middle lobe, lung, C34.3-lower lobe, lung, and C34.8-overlapping lesion of lung, C34.9-lung, not otherwise specified, were included in this study. Data on frequency and age were obtained from the database of Incidence-SEER 18 Research Data + Hurricane Katrina Impacted Louisiana Cases, November 2017 Sub, 1973–2015 varying. Data on the treatment are obtained from the database of Incidence-SEER 18 Regs Custom Data (with additional treatment fields), November 2017 Sub (1975–2015 varying). The surgical rate, radiotherapy rate, and chemotherapy rate were calculated manually. Data on incidence and survival rate were obtained from incidence 9 Regs Research Data, November 2017 Sub (1973–2015) <Katrina/Rita Population Adjustment>. The demographic and clinical data, including the year of diagnosis, age-adjusted incidence rates, age, sex, race/ethnicity, tumor stage, histopathologic types, treatment methods, and the 5-year relative rate, were used to estimate the changes in lung cancer over time. According to the SEER database, racial groups included white, black, other (American Indian/AK Native, Asian/Pacific Islander), and unknown racial patients. The data on unknown racial patients were omitted when calculating the incidence of different racial groups. The categories of lung cancer were defined by the 2015 WHO Classification of Lung Tumors.16Histopathological types were defined using ICD-O-3 His/behave, malignant. We calculated and analyzed the data of four histopathological types, namely ADC (8140/3, 8250/3, 8251/3, 8252/3, 8253/3, 8255/3, 8260/3, 8310/3), SCC (8070/3, 8071/3, 8072/3), LCC (8012/3, 8013/3), and SCLC (8041/3, 8044/3, 8045/3). Tumor stage was classified as localized, regional, and distant according to SEER historical stage A, which contained data from 1988 to 2015. The TNM stage system was not adopted because the staging criteria were not consistent over the years. Incidence rates were age-adjusted using the 2000 United States Standard Population, and all incidence rates were reported as age-adjusted incidence per 100,000 person-years.
Joinpoint Regression Program, version 184.108.40.206 (Statistical Methodology and Applications Branch, Surveillance Research Program, National Cancer Institute) was used to estimate the time periods of significant increases or decreases in rates via Joinpoint regression models. The Joinpoint regression models tested which trends (between joinpoints) were statistically significant and then estimated the annual percentage change (APC) in rates between the two joinpoint years. A maximum of three joinpoints was applied to characterize trends. P<0.05 was considered significant and all tests were two-tailed.
Ethics approval was exempted by the Ethics Committee of Zhongshan Hospital of Fudan University (Shanghai, China), as the SEER is a publicly available database, and data extracted from SEER were identified as nonhuman study. All patient data were anonymized.
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