OJPHI: Vol. 5
Journal Information
Journal ID (publisher-id): OJPHI
ISSN: 1947-2579
Publisher: University of Illinois at Chicago Library
Article Information
©2013 the author(s)
open-access: This is an Open Access article. Authors own copyright of their articles appearing in the Online Journal of Public Health Informatics. Readers may copy articles without permission of the copyright owner(s), as long as the author and OJPHI are acknowledged in the copy and the copy is used for educational, not-for-profit purposes.
Electronic publication date: Day: 4 Month: 4 Year: 2013
collection publication date: Year: 2013
Volume: 5E-location ID: e183
Publisher Id: ojphi-05-183

Mining Surveillance Data: Does Radiation Treatment of Prostate Cancer Cause Rectal Cancer?
John W. Morgan*12
Brice Jabo1
Mark E. Ghamsary1
Kevork Kazanjian3
1Dept Epidemiology, Biostatistics & Population Medicine, Loma Linda University School of Public Health, Loma Linda, CA, USA;
2Desert Sierra Cancer Surveillance Program, Region 5 of California Cancer Registry, Loma Linda, CA, USA;
3Dept of Surgery, Division of Surgical Oncology, Loma Linda University School of Medicine, Loma Linda, CA, USA
*John W. Morgan, E-mail: john.w.morgan@att.net

Abstract
Objective

We sought to assess whether external beam radiation (RAD) treatment of prostate cancer, that exposes the rectum to ionizing radiation, was followed by increased hazards for rectal cancer, relative to prostatectomy (SURG).

Introduction

Prostate cancer (PC) is the most common invasive cancer diagnosed among US men. The majority of PCs are organ-confined at diagnosis making them candidates for treatment using RAD, SURG, or other protocols. Several studies have provided preliminary evidence that radiation treatment of prostate cancer may increase subsequent rectal cancer risk (12). Data specifying type of RAD treatment of PC was not available for the study period.

Methods

We conducted record linkage for all 322,327 organ confined new prostate cancers and 53,204 new rectum and rectosigmoid junction (rectal) cancers among California males from 1988–2009, identifying men diagnosed with rectal cancer more than five years following treatment of organ-confined prostate cancer with RAD or SURG. Among the men treated with RAD vs SURG, the Cox proportional hazards ratio (HR) for subsequent rectal cancer was assessed. Demographic covariates included: race/ethnicity as Asian/Other (A-O), non-Hispanic black (NHB), Hispanic (Hisp), and non-Hispanic white (NHW), and socioeconomic status quintiles (1–5 Highest). Other covariates included age, as a continuous variable, and year of PC diagnosis.

Results

Among the 43,130 men having organ-confined prostate cancer that had been treated with RAD only, 166 were diagnosed with rectal cancer more than five years following PC treatment. Likewise, 69,104 men treated with SURG only, yielded 242 rectal cancer cases more than 5 years later. Following is the demographic factor adjusted hazards ratio (HR) for rectal cancer with 95% confidence intervals (CI) contrasting findings for the two PC treatment cohorts: Rectal cancer HRRAD/SURG=1.39; 95% CI=1.12–1.74. HR contrasts for demographic factors included age- (HRAge = 1.02; 95% CI=1.01–1.04), race/ethnicity- (HRA-O/NHW = 1.10; 95% CI=0.72–1.67, HRNHB/NHW = 1.19; 95% CI=0.82–1.74 and HRHisp/NHW = 1.01; 95% CI=0.72–1.43), and SES-contrasts (HRSES1/SES5 = 0.95; 95% CI=0.65–1.39), HRSES2/SES5=1.20;95% CI=0.89–1.62, HRSES3/SES5 = 1.17; 95% CI=0.88–1.55, and HRSES4/SES5 = 1.14; 95% CI=0.87–1.49). The HR for PC year of diagnosis (HRYear = 0.91; 95% CI=0.89–0.94) a protective effect for more recent years.

Conclusions

These findings reveal increased hazards for rectal cancer among organ-confined prostate cancer patients treated with RAD, relative to patients treated with SURG, that are substantially independent of demographic covariates. Treatment of rectal cancer among these patients is further complicated because they are ineligible for radiation treatment of rectal cancer due to the high-dose pelvic radiation received during prostate cancer treatment. Further analyses that seek to distinguish roles of different dose and delivery methods for RAD are ongoing.


References
1.. Rapiti E, Fioretta G, Verkooijen HM, Zanetti R, Schmidlin F, Shubert H, Merglen A, Miralbell R, Bouchardy C. Increased risk of colon cancer after external radiation therapy for prostate cancerInt. J. Cancer 123:1141–1145.2008;
2.. Baxter NN, Tepper JE, Durham SB, Rothenberger DA, Virnig BA. Increased Risk of Rectal Cancer After Prostate Radiation: A Population-Based StudyGastroenterology 2005;128:819–824.

Article Categories:
  • ISDS 2012 Conference Abstracts

Keywords: radiation, cancer, rectal, prostate, surveilance.




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