Graduation Year

2011

Document Type

Dissertation

Degree

Ph.D.

Degree Granting Department

Epidemiology and Biostatistics

Major Professor

Thomas J. Mason

Co-Major Professor

Heather G. Stockwell

Keywords

Chemotherapy, Gender Specific Survival, Lung Cancer, Lung Malignancy, Radiation Therapy, Surgery

Abstract

The objectives of this research were to test treatment and survival differences between women and men with lung cancer as there is minimal investigation in the literature. Three research questions were developed with statistical testing for gender differences based on similar cancer type, stage, treatment assignment and survival. Data for 44,863 primary lung cancer cases were collected from eight U.S. state-based cancer registries to investigate the research questions. The lung cancer incidence data included the morphological cell-types of adenocarcinoma (AC); squamous cell carcinoma (SCC); large cell carcinoma (LCC) and small cell carcinoma (SCC). Stage, grade, treatment type, as well as, individual characteristics such as gender, age at diagnosis, marital status at diagnosis and race were other variables obtained to be included in the statistical models.

Reporting the overall effect for lung cancer gender specific treatment differences or survival has not been demonstrated in the literature to the author's knowledge. By convention, main effects and interaction effects are reported in the literature; without including an evaluation the overall effect of a variable on the outcome, possible misinterpretations could be made. For example, utilizing the Cox's Proportional Hazards model when the interaction effect of gender and treatment type received was examined, females were at an increased risk for death by as much 29% as compared to males (HR = 1.18, 95% CI 1.09 - 1.29). But when the gender effect on survival was assessed, there was an increase in females survivorship as compared to males by as much as 28% (HR = 0.80, 95% CI 0.72 - 0.97 ).

In conclusion, by using a unique statistical approach, statistically significant Odds Ratios and Hazard Ratios were demonstrated for the research data set when the overall interaction effect on the outcome was examined. Recommendations to health care practitioners include adhering to current guidelines, e.g. American Medical Association, for lung cancer treatments. Standard treatment protocols were not always followed for early stage disease, e.g. females versus males with stage I lung cancer were 1.71 times more likely to receive chemotherapy in combination with radiation therapy versus a standard first treatment course of surgery (OR = 1.71, 95% CI 1.06 - 2.78). Also, depending on the lung cancer morphology and lung cancer treatment, females as compared to males could exhibit an increase in survivorship by as much as 28%. To improve the results of medical care decisions for lung cancer, clinicians may find the information presented in this study useful and encourage further research on which treatment increases survival for both men and women.

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