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Study of racial disparities in colorectal cancer screening using flexible sigmoidoscopy and cancer outcomes: An analysis of the PLCO Cancer screening trial.

Principal Investigator
Name
Sejong Bae
Institution
UAB
Position Title
PROFESSOR
Email
About this CDAS Project
Study
PLCO (Learn more about this study)
Project ID
PLCO-112
Initial CDAS Request Approval
Oct 29, 2014
Title
Study of racial disparities in colorectal cancer screening using flexible sigmoidoscopy and cancer outcomes: An analysis of the PLCO Cancer screening trial.
Summary
Colorectal cancer (CRC) is the third leading cancer related cause of death in the US1. Although the colorectal cancer incidence and mortality rates have been decreasing, both black males and females continue to have higher rates compared to other race categories2. Screening for CRC has the potential for reducing CRC incidence and mortality, provided that patients follow-through with recommendations based on a positive screening test. Variations in follow-through after a positive screening test may partly explain between group differences in cancer related outcomes. In a previous study of follow-up testing for prostate cancer in the National Cancer Institutes-Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial, it was observed that repeat testing was lower among NH black participants despite high odds of prostate cancer diagnosis and mortality3.
The benefits of endoscopic testing for CRC screening have been evaluated in the past and show that screening with flexible sigmoidoscopy was associated with significant decreases in CRC incidence (in both the distal and proximal colon) and mortality (distal colon only)4. In a population based study of CRC incidence, non-Hispanic blacks appeared to have more advanced disease and worse outcomes compared to other racial groups5.
Given the benefits of endoscopic screening, and that NH blacks have more advanced characteristics of CRC and worse outcomes compared to other racial groups, we would like to explore racial variations of CRC characteristics among individuals who have been randomized to the CRC screening arm of the PLCO Cancer Screening Trial. We hypothesize that (1) NH blacks are more likely to have a greater time between positive screening test and treatment, and that (2) more adverse characterization would be associated with this increased timing.
Aims

We hypothesize that (1) NH blacks are more likely to have a greater time between positive screening test and treatment, and that (2) more adverse characterization would be associated with this increased timing.
Methods:
The data will be obtained from colorectal site-specific set of analytic databases from the Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer screening trial. Data will be combined across the colorectal screening, incidence, and mortality datasets in order to gather our study’s variables and create the analysis dataset.
Our primary variable of interest will be the duration of time between a positive screening test and treatment as well as mortality. The cancer related outcomes of interest will include the CRC incidence and mortality rates. CRC incidence will be calculated as the number of CRC cancers divided by the total contributing person time; similarly CRC mortality rate will be calculated as the number of CRC reported deaths divided by contributing person time. Demographic covariates of interest included participant’s age, race, obesity, physical inactivity, diet, alcohol consumption, smoking status, family history of CRC, personal history of irritable bowel disease. These variables are all present in the colorectal dataset data dictionary.
In order to address our research questions and hypothesis we will compare the times between a positive screening test and treatment as well as mortality across race groups, as well as examine the association with mortality. The data and analyses will be described using Kaplan-Meier curves, Log rank tests, and Cox proportional hazard regression modelling.

Collaborators

Bradford E Jackson PhD
Karan P Singh PhD
Mohamed T. Jasser
Mona Fouad MD MPH
James Shikany PHD