Lethal prostate cancer is less-not more-likely to develop in patients with asthma. The Health Professionals Follow-up Study answers key questions about why.
Asthma often is considered to be a disease of chronic inflammation, particularly Th2 inflammation. Cancer often is thought of as mediated by Th2 inflammation. So the incidence of prostate cancer might be expected to be higher in patients with asthma.
But, surprisingly, lethal prostate cancer is less likely to develop in patients with asthma, according to a large study of men who completed questionnaires and allowed scientists to review their medical records.1
How did this paradoxical result come about? Let’s explore with some important questions.
1. How does the immune response influence the development of prostate cancer?
Some studies suggest that prostate cancer is linked to the kind of inflammation associated with asthma, which itself is a chronic inflammatory condition.
These Johns Hopkins researchers began looking at a possible connection between asthma and prostate cancer based on work in mice showing that the immune cells that infiltrate prostate tumors produce an immune response known as Th2 inflammation.1
A few other studies have analyzed the association between asthma and risk of prostate cancer, but the Johns Hopkins analysis differs in its larger size and its focus on lethal cancer cases.
2. How was the connection made between respiratory diseases and prostate cancer?
The researchers analyzed 47,880 men age 40 to 75 years who participated in the Harvard Health Professionals Follow-Up Study from 1986 through 2012 and did not have a cancer diagnosis before 1986. Study participants had completed a questionnaire every 2 years, reporting on demographic information, medical history, medication use, and lifestyle factors.1
The researchers evaluated the medical records and pathology reports for men who reported a prostate cancer diagnosis. Among them, 9.2% reported a diagnosis of asthma and 25.3% had received a diagnosis of hay fever. There were 798 confirmed lethal prostate cancer cases in the group.1
Men who had a medical history of asthma were 29% less prone to receive an advanced stage prostate cancer diagnosis. In addition, asthmatic men were 36% less prone to die from prostate cancer.
However, this is an observational study and it does not necessarily mean there is cause and effect. Also, links between a history of hay fever and lethal prostate cancer found a smaller but opposite association: Men with hay fever were 10% to 12% more likely to have lethal or fatal prostate cancer.1
3. Why might asthma not be linked to a higher risk of lethal prostate cancer?
Several possible reasons may explain why asthma might not be linked to a higher risk of lethal prostate cancer. The Th2 inflammation that drives asthma may not be the same as the Th2 inflammation that drives cancer. It also may be that asthmatics have higher levels of other immune cells, such as eosinophils or mast cells, that might attack tumor cells.
The Johns Hopkins collaborative team of immunologists and epidemiologists, among others, plans to go back into the laboratory to try to characterize the nature of the immune cells present in the prostate. They want to see what it is about a particular immune profile or immune environment that might be related to prostate cancer, especially aggressive prostate cancer.
• Paradoxically, asthma may protect against-rather than lead to-lethal prostate cancer.
• Patients with asthma are less likely to die from prostate cancer, but patients with hay fever are more likely.
• The immune response may influence how respiratory diseases affect the development of cancer.
1. Platz EA, Drake CG, Wilson KM, et al. Asthma and risk of lethal prostate cancer in the Health Professionals Follow-Up Study. Int J Cancer. 2015;137:949-958.