By David Douglas
NEW YORK (Reuters Health) - A 60-year follow-up of a clinical trial involving American Indian and Alaska Native schoolchildren shows a marked reduction in lung cancer in those who received BCG vaccination.
As Dr. Naomi E. Aronson told Reuters Health by email, "In this controlled trial, we show an association of the receipt of a single dose of BCG vaccine in school-aged children with a lifelong 2.5-fold decrease in all kinds of lung cancer, regardless of risk factors such as smoking or alcohol."
In this population, she added, "lung cancer is currently the leading cause of cancer mortality."
Dr. Aronson, of the Uniformed Services University of the Health Sciences, in Bethesda, Maryland, and colleagues followed up on a clinical trial with immunizations taking place between 1935 and 1938 in five U.S. states. A cumulative record review was also completed between 1992 and 1998.
The study included close to 3,000 American Indian and Alaska Native schoolchildren. All were under 20 years and none had evidence of previous tuberculosis infection. At a median of 8 years of age, 1,540 were randomized to BCG vaccination and 1,423 received placebo.
At the time of follow-up, 41% of the BCG group had died compared to 44% of the placebo group. A further 7% of the BCG group and 7% of placebo group could not be contacted, the researchers report in JAMA Network Open, online September 25.
There was no significant difference in cancer diagnosis between groups overall. This was also the case for lymphoma and leukemia which some previous studies have suggested might be increased in BCG-vaccinated populations.
However, after controlling for factors including smoking, alcohol overuse and tuberculosis, there was a significant difference in the rate of lung cancer. This was 18.2 per 100,000 patient years in the BCG group compared to 45.4 cases per 100,000 patient years in the placebo group (adjusted hazard ratio, 0.38; P=0.005).
"The clinical implications of this observation are to extend the reported nonspecific effects of BCG vaccine, and if confirmed in other long-term international cohorts from controlled BCG trials, to suggest that BCG vaccine could provide risk reduction for future lung cancer," Dr. Aronson concluded .
Dr. Mihai G. Netea of Radboud University Medical Center, Nijmegen, the Netherlands, who studies the non-specific effects of vaccines, told Reuters Health by email, "This is a study that adds to the increasing body of evidence for beneficial heterologous effects of BCG vaccination. Indeed, BCG instillations are currently routine treatment for bladder cancer, and earlier studies reported beneficial effects in lymphoma and melanoma."
Dr. Netea added, "This systematic epidemiological study reveals that BCG vaccination in early life has the capacity to decrease the risk for developing malignancies later on in life, especially lung cancer. This should lead to more studies to strengthen this observation on the one hand, as well as to understand the biological substrate of this effect on the other hand, as this may represent a novel target for immunotherapy in cancer."
JAMA Netw Open 2019.