12 Jun Women and Men Have Similar Colon Cancer Recurrence-Free Death Risk
MedicalResearch.com Interview with:
Prof. Catherine Quantin
Teaching Hospital, Department of Biostatistics and Medical Informatics France;
Dijon University Hospital, Clinical Investigation Center,
Clinical Epidemiology/Clinical Trials Unit, Dijon, France and
Dr Michal Abrahamowicz Ph.D
Department of Epidemiology, Biostatistics and Occupational Health
McGill University, Montreal, Canada
Medical Research: What is the background for this study?
Response: One difficulty, common to prognostic studies of cancer, concerns the need to separate the effects of prognostic factors on different clinical endpoints, such as disease recurrence vs recurrence-free death. Some published prognostic studies used a Cox regression model that included recurrence as a time-dependent covariate, to assess the impact of recurrence on mortality, and to adjust for recurrence when estimating the effects of other prognostic factors on mortality. However, the Cox model is limited to the assessment of the effects of covariates on a single endpoint, such as death. This limitation is overcome by multi-state models, that make it possible to model alternative pathways of disease progression and to assess the impact of prognostic factors on both recurrence-free death vs death after recurrence, and recurrence followed by death.
Another difficulty, is that the cause of death is not available or not accurately coded. Yet, some patients are likely to die of causes not related to the disease of primary interest, especially in cancers with longer survival and in those that affect older subjects. The effects of prognostic factors estimated with Cox model, or classic multi-state models, are not able to discriminate between their effects on the mortality due to cancer of primary interest vs natural mortality. However, age is a very strong predictor of overall mortality, but is not systematically associated with higher cancer-specific mortality.
To deal with this difficulty, many prognostic studies use relative survival methods.
The general idea is to use the mortality tables for the relevant general population to estimate survival corrected for the expected natural mortality, due to other causes of death.
Medical Research: What are the main findings?
Response: Relative survival multistate model provides more information on prognosis and expected outcomes of patients with different characteristics than usual models (Cox or non multi-state relative survival models).
Medical Research: What should clinicians and patients take away from your report?
- Women with colorectal cancer have a similar risk of recurrence-free death to men.
- Almost all deaths among patients who had recurrence were due to colorectal cancer.
- Many deaths among patients without recurrence may be due to natural causes, not related to colorectal cancer.
Medical Research: What recommendations do you have for future research as a result of this study?
Response: Future prognostic registry-based studies of different cancers should consider the relative survival multi-state Markov analyses.
Prof. Catherine Quantin, Teaching Hospital, Department of Biostatistics and Medical Informatics France and Dr Michal Abrahamowicz Ph.D, Department of Epidemiology, Biostatistics and Occupational Health, & McGill University, Montreal, Canada (2015). Women and Men Have Similar Colon Cancer Recurrence-Free Death Risk