RETROSPECTIVE COHORT STUDY OF INCIDENT RECTAL CANCER FOLLOWING RADIATION TREATMENT FOR PROSTATE CANCER Open Access

Abstract

Abstract

RETROSPECTIVE COHORT STUDY OF INCIDENT RECTAL CANCER
FOLLOWING RADIATION TREATMENT FOR PROSTATE CANCER
By Emily K. McCollum
The association between prostate cancer radiation treatment and subsequent rectal cancer
risk has not been well examined in the past. The current investigation seeks to add to the
existing evidence by differentiating between the two major forms of radiation treatment
used for prostate cancer, external beam radiation (EBRT) and brachytherapy. A cohort of
men diagnosed with prostate cancer between 1995 and 2008 was obtained from the
Surveillance Epidemiology and End Results database. Data was analyzed using a Cox
proportional hazards model stratified by race and the results were expressed as adjusted
hazard ratios (HRs) and the corresponding 95% confidence intervals (CIs).
Brachytherapy was associated with the largest increase in rectal cancer rates with HR
(95% CIs) of 1.24 (1.22-1.26) for whites, 1.27 (1.20-1.34) for blacks, 1.29 (1.19-1.40)
for Asians/Pacific Islanders and 1.17 (1.01-1.35) for persons whose race was unknown or
not reported. There was no association between EBRT and rectal cancer incidence with
HR estimates in the 0.94-1.03 range and all CIs including unity. The corresponding HRs
for EBRT plus brachytherapy were also significantly elevated in almost all race
categories (except for those patients whose race was unknown), but the magnitude of the
association was lower than that for brachytherapy alone. The cause of this difference
between the two main radiation treatments cannot be fully discerned without access to
data on dosage and duration. If confirmed, these results should be used to inform patients
and their physicians in making prostate cancer treatment decisions and in monitoring log-
term treatment outcomes.

Table of Contents

TABLE OF CONTENTS

BACKGROUND/LITERATURE REVIEW .......................................................................................... 1
Introduction ............................................................................................................................ 1
Treatment Options ................................................................................................................... 1
Long-term effects of radiation therapy ........................................................................................ 3
Current study objectives ........................................................................................................... 4
METHODS ............................................................................................................................... 5
RESULTS ................................................................................................................................. 7
DISCUSSION ........................................................................................................................... 8
CONCLUSIONS ....................................................................................................................... 10
TABLES ................................................................................................................................. 12
FIGURES................................................................................................................................ 14
REFERENCES ......................................................................................................................... 16
APPENDICES
APPENDIX I: SEER Data Use Agreemen
APPENDIX II: IRB exemption clarification, email correspondence

About this Master's Thesis

Rights statement

• Permission granted by the author to include this thesis or dissertation in this repository. All rights reserved by the author. Please contact the author for information regarding the reproduction and use of this thesis or dissertation.

School	Rollins School of Public Health
Department	Epidemiology
Degree	MPH
Submission	Master's Thesis
Language	English
Research Field	Health Sciences, Public Health Health Sciences, Oncology Health Sciences, Epidemiology
Keyword	Rectal Cancer Secondary cancers Radiation Treatment External Beam Radiation Prostate cancer Brachytherapy
Committee Chair / Thesis Advisor	Goodman, Michael, Emory University
Partnering Agencies	Does not apply (no collaborating organization)

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