Cancer incidence in a general population of Asthma patients.
Pharmacoepidemiology and Drug Safety 2006;15:131-8.
ABSTRACT
Methods: We performed a cohort study with a nested case-control
analysis using the General Practitioner Research Database in the UK.
We defined three cohorts: patients with asthma, patients with COPD,
and general population. During the follow up we identified a total of
5,263 incident cases of cancer. We conducted a nested case-control
analysis that included all cancer cases as well as 20,000 frequency
matched controls free of cancer frequency matched on age, sex, and
calendar year.
Results: Patients with asthma did not have greater overall risk of
cancer compared with the general population (Odds ratio=0.93, 95%
Confidence interval:0.86-1.00). However, they presented an elevated
risk of experiencing lung cancer (Odds ratio=1.84, 95%Confidence
interval: 1.58-2.15). after controlling Controlling for smoking and
other potential confounding factors yielded a much lower estimate
(Odds ratio =1.35, 95% Confidence interval:1.15-1.59). This estimate
contrasted with that observed for non smoking related cancer (0.87,
95%Confidence interval: 0.80-0.94)) Overall, respiratory drugs did not
seem to be strongly associated with cancer among asthmatic patients.
Patients with COPD had an Odds ratio of cancer of 1.26 (95% Confidence
interval:1.12-1.43) compared with the general population.
Conclusion: Asthma does not seem to be associated with an increased
risk of cancer. In fact the risk of non smoking related cancer appears
to be somewhat reduced. However, we observed an elevated risk of lung
cancer among asthmatic patients. Whether this result is a due to
residual confounding and/or protopathic bias remains unclear. Further
investigation is warranted to confirm or discard these associations.
Purpose: Several studies have assessed the association between asthma
and cancer but none of them revealed a clear pattern of association of
asthma with incidence of cancer. We aimed to examine the association
between asthma, chronic obstructive pulmonary disease (COPD) and
cancer.