Efforts to link environmental factors to cancer have foundered recently, as highlighted in an article by New York Times science reporter, Gina Kolata.
But those who subscribe to the cancer cluster theory still aren't satisfied. So how do you explain an alleged increased rate of cancer in a small area? Our Cancer Clusters: Findings vs. Feelings addressed some of the key weaknesses in the theory that they can be chalked up to manmade causes such as industrial chemicals.
But now there is a new chink in the activist armor. Infections could be a cause of some childhood cancers, according to a study published this week. This study, which is consistent with earlier research, challenges the notion that environmental toxins are to blame for alleged clusters of childhood cancers.
Dr. Richard McNally, of the University of Newcastle upon Tyne in England found that leukemia, the most common type of childhood cancer, may be triggered by an "infection in a mother while she is carrying her baby," or be triggered if a child is infected with certain viruses while young.
"These could be minor, common illnesses, such as a cold, mild flu, or a respiratory infection," said McNally. While the study is still preliminary, and the infection theory is still just a theory, the study, published in The European Journal of Cancer's December issue, supports earlier notions regarding viruses and cancer.
Dr. McNally points out that "These findings are consistent with previous studies that have shown that delayed exposure to infections probably leads to an increased risk of leukaemia and, for the first time, suggests it may also increase the risk of brain tumours."
While many are surprised that a virus could play a role in cancer causation, the notion is nothing new. After all, it is well established that human papilloma virus (HPV) plays a role in the cause of cervical cancer, hepatitis B causes liver cancer, and, according to the National Institutes of Health, "People with AIDS are particularly prone to developing various cancers, especially those caused by viruses such as Kaposi's sarcoma and cervical cancer, or cancers of the immune system known as lymphomas."
Perhaps the finding in the British study that most strongly supports the virus-cancer link (and runs counter to the environmental toxins explanation) is that brain tumors and leukemia occurred not only in similar geographical locations, but at similar times. This "space-time" clustering is a pattern typical of diseases caused by infection. Since the presence of chemicals, power lines, or other alleged cancer risks is likely to be persistent or increasing, any cancers caused by such environmental factors would reflect that steady or growing level of exposure. But that wasn't the case. Rather, cancer rates increased only at particular times, in the same pattern that infections spread and then decrease.
Cancer clusters may not even exist. But if you insist on believing they do, Dr. McNally's research provides a most compelling, albeit preliminary, explanation.
Jeff Stier, Esq., is an associate director of the American Council on Science and Health (ACSH.org, HealthFactsAndFears.com).
