Antibiotic use has been linked to a number of different cancers such as breast cancer, lung cancer and colorectal cancer, almost certainly because antibiotics cause long-term damage to the gut microbiome and damage the lymphocytes in the immune system.
Over 70 billion doses of antibiotics were prescribed in 2010 worldwide and it is estimated that at least half were given for conditions they could not treat. Millions of people suffered damage more than a decade ago. Imagine the situation now, 15 years on!
As you will also read, antibiotic use during cancer treatment can lower progression-free survival and overall survival.
Breast cancer and antibiotic use
The Journal of the American Medical Association (Feb 18, 2004; 291:827-35) reported a study of 10,000 women. Those who took antibiotics for more than 500 days in a 17 year period held more than twice the risk of breast cancer as women who had taken none. Women who had taken just one dose of antibiotics statistically increased their risk by 1.5 times.
The likely explanation might involve the action of antibiotics in destroying good bacteria in the gut and causing dysbiosis in the microbiome. We have a review on how antibiotics scar the gut. This could lead to a lowered immune system, to the loss of important compounds that commensal bacteria make (B vitamins, melatonin, serotonin etc.), inflammation and the uncontrolled growth of certain 'bad' bacteria such as E.coli.
The researchers argued that it could also be simply a case of women who get more infections have weaker immune systems and may be more prone to cancer. But they knew little about the importance of the microbiome to your health at that time. The study followed up on original findings in Finland in 2000 where the first connection was made.
In 2023 Stanford Medicine showed (1) in women with Triple Negative Breast Cancer who took multiple antibiotic prescriptions within three years from diagnosis were more likely to experience recurrence and to die from their cancer than those who took fewer courses of the drugs. However, the effect on survival had nothing to do with cancer severity. "Each additional antibiotic increased the risk of death between 5% and 18% relative to patients who weren't prescribed antibiotics," said Dr Julia Ransohoff. Researchers found that the antibiotics (and antifungals lowered levels of lymphocytes. And lowered numbers of lymphocytes mean lower survival times.
Lung cancer and antibiotics
As long ago as 2008, a review of cases (2) of lung cancer showed "an increased risk of lung cancer associated with prescription antibiotics". The researchers do state that more antibiotics are prescribed for people who have more chest infections. But their conclusion is clear. There is also now known to be a Gut-Lung axis. If you damage the gut microbiome, you will damage the lung microbiome. Attention to the Gut-lung axis is crucial in fighting lung cancer.
In 2021 a study (3) of 27,017 cases and 129,355 controls showed that recent exposure to antibiotics, was twice as likely in the lung cancer cases, and proximity to diagnose and greater number of prescriptions were clear factors. These findings were not affected by sex, but the older you were the stronger the findings.
Lung cancer is now being treated using chemo and a PD-1 immunotherapy. Research has shown that prior use of antibiotics, and also during the treatment are both linked to lower progression free survival and to lower overall survival (4).
Antibiotics and Colorectal cancer
Antibiotic use is known to lead to a disturbed microbiome (dysbiosis) and other illnesses such as IBS, Crohn's, colitis, diverticulitis, Hashimoto's and more. Not only does antibiotic use seem to be linked to more cases of colorectal cancer, but the type of antibiotic and the location of the cancer - bowel, anal etc. - seem to be linked (5).
An overgrowth of yeasts/fungi after antibiotic use is common. Normally your healthy bacteria consume such yeasts at night time while you sleep. Candida albicans is known to colonise the gut and even areas of the body and it can reduce oxygen in those local areas as it is an anaerobe. Cancer thrives in low oxygen conditions. We have a separate article where three studies show antibiotics increase Colorectal cancer risk.
Go to: Colorectal cancer cases increasing in the young
*********
References
- Antimicrobial exposure is associated with decreased survival in triple-negative breast cancer; Julia D. Ransohoff et al; Nature Communications, Published: 12 April 2023
- Antibiotic use and the risk of lung cancer; Cancer Epidemiol Biomarkers Prev (2008) 17 (6): 1308–1315.
- Antibiotic use prior to a lung cancer diagnosis: a population-based study; Lukas Löfling et al; Cancer Causes Control. 2021, Mar 22;32(6):597–607.
- Antibiotics are associated with worse outcomes in lung cancer patients treated with chemotherapy and immunotherapy; Elkrief, A., Méndez-Salazar, E.O., Maillou, J. et al; npj Precis. Onc. 8, 143 (2024). https://doi.org/10.1038/s41698-024-00630-w
- Oral antibiotic use and risk of colorectal cancer in the United Kingdom, 1989–2012; https://gut.bmj.com/content/68/11/1971