Graduation Date

Spring 5-5-2018

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Programs

Epidemiology

First Advisor

KM. Monirul Islam, MD, MPH, PhD

Abstract

Lung cancer is the second most commonly diagnosed cancer and the leading cause of cancer mortality of both genders in the United States. A recent report suggests that the relative five-year survival rate of lung cancer is only 18%. Studies indicate many factors are associated with the survival of lung cancer patients, including age at diagnosis. It is widely known as a disease of older people, but the literature shows a substantial number of young people have been diagnosed with lung cancer. The literature also indicates that the refusal of recommended treatment contributes to cancer-related death and poorer survival. The objectives of this dissertation were to estimate the survival of lung cancer patients, examine the effect of treatment refusal on survival, and investigate factors associated with treatment refusal. To address these objectives, we conducted our analyses using two large cancer databases: the Veterans Affairs Central Cancer Registry and the National Cancer Database. We performed statistical data analyses using logistic regression, the Kaplan–Meier survival estimator, and Cox regression (proportional hazards regression) method. The results indicate a better five-year survival among younger-onset patients compared with older-onset patients, particularly among early-stage cancer. In the multivariable analyses, treatment refusal was associated with higher mortality risk. Furthermore, our results suggested that patients of older age at diagnosis, female gender, with comorbid conditions, and uninsured status were more likely to refuse recommended lung cancer treatment. In this dissertation, we could not analyze other relevant factors, such as types of comorbidity, patient’s performance status, treatment side effects, family history of lung cancer, and cost of treatment, due to data limitation. Adjusting such factors in future studies will provide a more robust comparison of survival and genetic differences between younger- and older-onset lung cancer cases. Future studies should also examine patients’ and clinical aspects of cancer education and patient–physician communication materials to improve patient acceptance of lung cancer treatment.

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