Description of a Lung Cancer Hotspot: Disparities in Lung Cancer Histology, Incidence, and Survival in Kentucky and Appalachian Kentucky

Abstract

Introduction: Kentucky is recognized as the state with the highest lung cancer burden for more than 2 decades, but how lung cancer differs in Kentucky relative to other US populations is not fully understood.

Patients and methods: We examined lung cancer reported to the Surveillance, Epidemiology, and End Results (SEER) Program by Kentucky and the other SEER regions for patients diagnosed between 2012 and 2016. Our analyses included histologic types, incidence rates, stage at diagnosis, and survival in Kentucky and Appalachian Kentucky relative to other SEER regions.

Results: We found that both squamous cell carcinomas and small-cell lung cancers represent larger proportions of lung cancer diagnoses in Kentucky and Appalachian Kentucky than they do in the SEER registries. Furthermore, age-adjusted cancer incidence rates were higher in Kentucky for every subtype of lung cancer examined. Most notably, for Appalachian women the rate of small-cell carcinomas was 3.5-fold higher, and for Appalachian men the rate of squamous cell carcinoma was 3.1-fold higher, than the SEER rates. In Kentucky, lung cancers were diagnosed at later stages and lung cancer survival was lower for adenocarcinoma and neuroendocrine carcinomas than in SEER registries. Squamous cell carcinomas and small-cell carcinomas were most lethal in Appalachian Kentucky.

Conclusion: Together, these data highlight the considerable disparities among lung cancer cases in the United States and demonstrate the continuing high burden and poor survival of lung cancer in Kentucky and Appalachian Kentucky. Strategies to identify and rectify causes of these disparities are discussed.

Keywords: Appalachia; Disparities; Interventions; Small cell; Squamous.

Figure 1

Histological distributions and incidences of lung cancer in Kentucky differ significantly from SEER data. (A) First primary tumors from the indicated databases were classified into 5 major non–small-cell lung cancer histological subtypes. Percentages of each subtype are shown for all patients (men and women), only male patients, and only female patients. SEER = SEER database without Kentucky data. (B) Incidence of lung cancer as a first primary tumor was adjusted for age and subclassified into the 5 major histological groups of non–small-cell lung cancer. SEER = Surveillance, Epidemiology, and End Results database without Kentucky data; NAP KY = non-Appalachian Kentucky; AP KY = Appalachian Kentucky.

Figure 2

Non–small-cell neuroendocrine carcinomas are diagnosed at later stage and are higher grade in Kentucky than in SEER. (A) First primary neuroendocrine carcinomas were categorized as either localized, regional, or distant in the database. The percentage of each group is shown. (B) Non–small-cell neuroendocrine histology codes were segregated into 3 categories of increasing grade. The percentage of each group is shown. SEER = Surveillance, Epidemiology, and End Results database without Kentucky data; NAP KY = non-Appalachian Kentucky; AP KY = Appalachian Kentucky.

Figure 3

Subtype-specific lung cancer survival rates are often significantly lower in Kentucky. (A) Overall survival of first primary lung malignancies was calculated for each of the 5 major histological subgroups of non–small-cell lung cancer. These data represent the SEER database including Kentucky. (B) Overall survival of first primary lung malignancies was calculated for each of the 5 major histological subgroups of non–small-cell lung cancer. The data were further grouped as either SEER without Kentucky and compared with Kentucky overall, or grouped as only Kentucky and compared Appalachian to non-Appalachian Kentucky. Mantel-Cox log-rank P values are shown, significant P values are in red. SEER = Surveillance, Epidemiology, and End Results database without Kentucky data; NAP KY = non-Appalachian Kentucky; AP KY = Appalachian Kentucky.