title: Differential effects of patient-related factors on the outcome of radiation therapy for rectal cancer.
abstract: OBJECTIVE
  The objective of this study was to investigate whether cancer specific survival in rectal cancer patients is affected by patient-related factors, conditional on radiation treatment.
  
  
  METHODS
  359 invasive rectal cancer patients who consented and provided questionnaire data for a population-based case-control study of colorectal cancer in Metropolitan Detroit were included in this study. Their vital status was ascertained through to the population-based cancer registry. Hazard ratios (HR) for cancer specific and other deaths and 95% confidence intervals (CIs) were calculated according to selected patients' characteristics, stratified by radiation status, using joint Cox proportional hazards models.
  
  
  RESULTS
  A total of 159 patients were found to be deceased after the median follow-up of 9.2 years, and 70% of them were considered to be cancer specific. Smoking and a history of diabetes were associated with an increased probability of deaths from other causes (HR 3.20, 95% CI 1.72-5.97 and HR 2.02, 95% CI 0.98-4.16, respectively), while regular use of non-steroidal anti-inflammatory drugs (NSAIDs) was inversely correlated with cancer-specific mortality (HR 0.50, 95% CI 0.30-0.81). Furthermore, the associations of smoking and NSAIDs with the two different types of deaths (cancer vs others) significantly varied with radiation status (P-values for the interactions= 0.014 for both). In addition, we observed a marginally significantly reduced risk of cancer specific deaths in the patients who had the relative ketogenic diet overall (HR=0.49, 95% 0.23-1.02).
  
  
  CONCLUSIONS
  Further research is warranted to confirm these results in order to develop new interventions to improve outcome from radiation treatment.
authors.affiliation: Department of Oncology, Wayne State University School of Medicine, Detroit, USA; Department of Pathology, Wayne State University School of Medicine, Detroit, USA.
authors.forename: Ikuko
authors.initials: I
authors.lastname: Kato
authors.affiliation: Department of Oncology, Wayne State University School of Medicine, Detroit, USA.
authors.forename: Gregory
authors.initials: G
authors.lastname: Dyson
authors.affiliation: Department of Radiation Oncology Wayne State University School of Medicine, Detroit, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Snyder
authors.affiliation: Department of Pathology, Wayne State University School of Medicine, Detroit, USA.
authors.forename: Hyeong-Reh
authors.initials: HR
authors.lastname: Kim
authors.affiliation: Department of Family Medicine and Public Health Sciences, Wayne State University School of Medicine, Detroit, Michigan, USA.
authors.forename: Richard K
authors.initials: RK
authors.lastname: Severson
keywords: Non-steroidal anti-inflammatory drugs; diet; rectal cancer; smoking; survival