Summary: Asthma, allergy and the risk of prostate cancer: results from the Montreal PROtEuS study
Deborah Weiss, Mariam El-Zein, Marie-Claude Rousseau, Hugues Richard, Pierre I. Karakiewicz, Marie-Élise Parent
The relationship between allergies and cancer is still unclear, with different results depending on both the type of cancer and the specific allergic disease under investigation. In the case of prostate cancer, the link with allergies is not yet understood. In this study – the largest ever published on the topic – the researchers examined the association between allergic conditions and prostate cancer risk in detail. They explored the possible influence of current versus former allergic conditions (allergy, hay fever, and asthma), age at onset, time since onset, and duration of each allergic condition. Interestingly, this was the first time that the effect of asthma duration on prostate cancer risk was taken into consideration and only the second time that the effect of age at asthma onset was studied.
The researchers did not find any evidence of an association between each condition, or having both groups of conditions, and prostate cancer, in terms of both risk and severity of the disease. Moreover, the risk didn’t change according to status (current or former allergy), age at onset, time since onset, or duration of each allergic condition.
The use of self-reported information and misclassification of allergy status could have helped lead to this conclusion, but the prevalence of both asthma (8-9%) and allergy (13%) in the study population matched that which is expected among Canadian adults. This held true for both cases and control. As another measure of confirmation, self-reporting of allergic conditions has been shown to be highly accurate.
In addition to taking age, ancestry, prostate cancer screening history and family history into account when conducting their analyses, the detailed medical history collected during interviews with the 1936 cases and 1995 controls in Montreal also elicited information on anti-asthmatic medication. While the interviewers involved did not specifically request such information, it’s notable that the 20% of asthmatics that did report taking any anti-asthmatic were at an almost two-fold increased risk of prostate cancer. Normally 60-70% of asthmatics take medication, though, so this voluntary reporting should be interpreted with caution. If this suggestion of elevated risk is confirmed, it would support the idea that the chronic inflammation associated with allergic disease can lead to increased cancer risk.
While this study was very strong given its large size, detailed lifetime medical history, and its ascertainment of cases, future studies investigating the association between asthma, allergy, and cancer could be improved by including assessment protocols considering the timing and duration of allergic disease exposure.