BCG vaccination linked to reduced incidence of lung cancer
medwireNews: Receipt of the Bacillus Calmette-Guérin (BCG) vaccine may reduce the risk for developing lung cancer, suggests a secondary analysis of a clinical trial conducted in American–Indian and Alaska Native populations.
Naomi Aronson (Uniformed Services University of the Health Sciences, Bethesda, Maryland, USA) and colleagues found that patients given the BCG vaccine had a 2.5-fold lower rate of lung cancer than patients not given the vaccine.
They emphasize that “this is the first analysis to show a protective association of BCG vaccination with lung cancer,” and add: “Given the high mortality rate of cancer and the low cost of BCG vaccines, our data could have important public health implications.”
The team used data from a placebo-controlled trial of the BCG vaccine (strain 317 or 575) that enrolled 3287 American–Indian and Alaska Native participants from five US states between 1935 and 1998. The present analysis included 2963 of the participants, of whom 1540 were in the vaccine group and 1423 in the placebo group.
During 60 years of follow-up, there was no significant difference in the overall rate of cancer diagnosis between the BCG vaccine and placebo groups, at 222 and 262 cases per 100,000 person–years, respectively.
However, the incidence of lung cancer was significantly lower among individuals who received vaccination than those who did not, at 18.5 versus 45.4 cases per 100,000 person–years, which equated to a 62% reduced risk for developing lung cancer with receipt of the vaccine, after taking into account factors such as sex, alcohol overuse, and smoking.
Of the other evaluated risk factors, smoking history or missing smoking history were significantly associated with an increased incidence of lung cancer (hazard ratios [HRs]=2.44 and 5.29, respectively).
By contrast, alcohol overuse or missing alcohol history were associated with a reduced incidence (HRs=0.33 and 0.26), which the researchers state “likely reflects competing risks (ie, liver failure, pancreatitis, and other cancers).”
Additionally, a prior tuberculosis diagnosis was not associated with a higher risk for lung cancer, leading the authors to comment that these data “are consistent with existing research indicating that BCG vaccination is associated with diverse immunological effects independently of [tuberculosis].”
The researchers note that previous studies have found “increased rates of lymphoma and leukemia in BCG-vaccinated populations.” However, the current analysis identified similar rates of both types of malignancy in the patients given BCG and those given placebo.
By Hannah Kitt
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