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Does the timing of comorbidity affect colorectal cancer survival? A population based study
  1. Lorraine G Shack1,2,
  2. Bernard Rachet1,
  3. Evelyn M I Williams3,
  4. John M A Northover4,
  5. Michel P Coleman1
  1. 1Cancer Research UK Cancer Survival Group, London School of Hygiene and Tropical Medicine, London, UK
  2. 2Health Promotion, Disease and Injury Prevention, Alberta Health Services, SW Calgary, Alberta, Canada
  3. 3Division of Public Health, School of Population, Community and Behavioural Sciences, Whelan Building, University of Liverpool, Liverpool, UK
  4. 4Imperial College of Science, Technology and Medicine, St Mark's Hospital, Harrow, UK
  1. Correspondence to Lorraine G Shack, Research and Evaluation Unit, Alberta Health Services, 2210 2nd Street SW, Calgary, Alberta T2S 3C3, Canada; lorshack{at}


Objectives Comorbid conditions in colorectal cancer patients can influence both clinical eligibility for treatment and survival. We aimed to evaluate the effect of comorbidity on 1 year survival from colorectal cancer, and to assess whether this effect varied with the timing of the comorbidity in relation to the cancer diagnosis.

Study design and setting A population based cohort of 29 563 colorectal cancer patients diagnosed between 1997 and 2004 in the North West of England was evaluated. The excess hazard of death up to 1 year after diagnosis was estimated using deprivation and region specific life tables to adjust for background mortality. Results were adjusted for age and stage at diagnosis.

Results Comorbid conditions diagnosed during the period 18 to 6 months before the diagnosis of colorectal cancer were strongly associated with lower survival at 1 year. Stage and age remained the strongest predictors of cancer related mortality even after adjustment for comorbidity.

Conclusions Administrative data provide a good estimate of the prevalence of most comorbid conditions but may be biased for some comorbid conditions that can be contra-indicators for cancer treatment. The time window in which a comorbid condition occurs in relation to the cancer diagnosis should be taken into account. Adjustment should be carried out, where possible, to provide more robust and clinically appropriate comparisons of population based cancer patient survival.

  • cancer
  • colorectal
  • cancer registry
  • comorbidity
  • survival
  • excess mortality
  • relative survival
  • oncology
  • epidemiology

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  • Funding The Cancer Survival Group at the London School of Hygiene and Tropical Medicine is funded by Cancer Research UK (grant no. C1336/A5735). Lorraine Shack was supported by the North West Cancer Intelligence Service; this work was undertaken as part of a PhD thesis.

  • Competing interests None.

  • Ethics approval Liverpool Research Ethics Committee (06/Q1505/14); Patient Information Advisory Group (2-05(g)/2006) and London School of Hygiene and Tropical Medicine Ethics Committee (5056).

  • Provenance and peer review Not commissioned; externally peer reviewed.