Cholera vaccination may lower risk of death from colorectal cancer
By Scott Baltic
NEW YORK (Reuters Health) - Cholera vaccination after a diagnosis of colorectal cancer (CRC) is associated with reduced risks of death from CRC and from any cause, according to data from a Swedish study.
“To our best knowledge, this is the first nationwide population-based study to explore the association between post-diagnostic use of cholera vaccine and the risk of mortality in CRC patients,” the researchers write.
Dukoral, the vaccine used in the study, includes both inactivated Vibrio cholerae O1 and recombinant cholera toxin B (CTB) subunit.
“Previous studies found that cholera toxin might have multiple functions with the ability to regulate the immune system. In addition, it can reduce the development of colon polyps in mouse models of CRC,” lead author Dr. Jianguang Ji of Lund University and Skane University Hospital, Malmo, Sweden, told Reuters Health by email.
CRC is much more common in developed countries than in developing ones, he noted, which supports the hygiene hypothesis that lack of exposure to microbes during childhood might be related to future development of CRC.
Ji and colleagues used Sweden’s national cancer registry and national prescribed drug registry to retrospectively identify 175 CRC patients who had been prescribed cholera vaccine after cancer diagnosis from mid-2005 through 2012 (minimum follow-up, 3 years). The reasons for the cholera vaccination were unknown, but the patients may have needed it for travel outside Sweden.
The study’s findings were published online September 15 in Gastroenterology.
Patients vaccinated against cholera after CRC diagnosis had lower risks for CRC mortality (by 47%) and overall mortality (by 41%), compared with 525 unvaccinated controls. The survival advantages were “largely consistent irrespective of age at diagnosis, gender, and stage at diagnosis of CRC,” the authors write.
Given the findings, the authors hypothesize that CTB can inhibit CRC progression by promoting immune cells, such as CD8+ T cells, macrophages and NK (natural killer) cells, and/or by affecting genes that are related to tumorigenesis.
“If our findings can be confirmed by other population-based studies or other randomized clinical trials, cholera vaccine might be used as adjuvant therapy for patients with CRC,” Dr. Ji concluded.
“There’s been accumulating scientific and medical evidence that microbes or their products stimulate the immune system and impart a wide range of health benefits, protecting from some types of cancers and other immune-mediated diseases,” Dr. Susan Erdman of the Massachusetts Institute of Technology told Reuters Health by email. Erdman, whose MIT laboratory focuses on microbe-triggered inflammatory processes and cancer, was not involved with the current study.
“In the context of the hygiene hypothesis, wherein modernized human living has too few microbe exposures for immune system health,” she explained, “a safe oral vaccine that boosts immune resiliency has enormous promise for public health goals.”
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