When I came across a report about a new study connecting antibiotic use with risk of colon cancer, I knew it was worth sharing.

Here’s the backstory: In April 2021, Akimoto et al. published an article entitled “Rising Incidence of Early-Onset Colorectal Cancer – A Call to Action.”^[i] They wrote:

The incidence of early-onset colorectal cancer (CRC), which occurs in individuals <50 years of age, has been increasing worldwide and particularly in high-income countries. The reasons for this increase remain unknown but plausible hypotheses include greater exposure to potential risk factors, such as a Western-style diet, obesity, physical inactivity and antibiotic use, especially during the early prenatal to adolescent periods of life.

Due to such exposure, not only can mutations occur in the cells that form the intestinal lining, but gut bacteria (gut microbiome) are affected in the way their activity interrelates with the immune system. In other words, we already know that the colorectal system is endangered by lifestyle factors we often take for granted. But what leaps out in the Akimoto paper is antibiotic use in early life as a possible catalyst for colorectal cancer, and the fact that early-onset CRC is on the rise!

Early-onset CRC

What does “early onset” mean? It refers to CRC that strikes individuals younger than 50. While an increase of early-onset CRC has been observed around the world, in the U.S. it’s been on the rise since the mid-1990s, from 5.9 to 8.4 cases per 100,000 persons between 2000-2017.^[ii]

Also, early-onset CRC may be biologically different than CRC that occurs later in life. Studies report different cellular characteristics between the two. Younger CRC patients are more often diagnosed when their cancer is already at a later stage (stages III-IV), when it’s a more threatening disease. This is possibly due to less awareness of CRC at younger age, lack of screening, and reluctance to seek testing and medical care. Thus, the prognosis (probable outcome) for these patients is worse.

New study links early-onset CRC with antibiotics

On July 2, Sarah Perrott, a medical student at the University of Aberdeen (Scotland), presented results of a new study at the ESMO World Congress on Gastrointestinal Cancer 2021. The study is noteworthy because it may be the first to specifically analyze data for a relationship between antibiotics and CRC—though as we saw from the Akimoto paper, it was already a suspected culprit.

The U of Aberdeen team used Scottish primary care records to identify CRC cases diagnosed from 1999-2011. They included 7903 CRC cases (5281 colon cancer, 2622 rectal cancer) and over 30,000 healthy controls. Each CRC case was matched with up to 5 controls, and all cases were divided into two age groups (younger than 50 vs. 50 or older. 445 (5.6%) of CRC cases were under 50 at diagnosis.

The team took into account the history of antibiotic use for all cases, with the period of time for exposure divided into 0, 1-15, 16-60, and > 60 days. They discovered that 45% of the CRC cases had been prescribed any previous antibiotic use, and these cases had significantly increased colon cancer risk—but it was most pronounced in those under 50, especially those with total antibiotic exposure of 1-15 days. Compare this with those diagnosed at age 50 or above, where no such link was observed. Interestingly, no significant relationship between antibiotics and rectal cancer was found.

Perrott herself pointed out that their study suggests unnecessary antibiotics should be avoided, especially in children and young adults. More research is needed to identify the processes by which antibiotics may be altering the gut microbiome in ways that make the colon more vulnerable to cancer, particularly in younger people.

Antibiotics and prostate cancer

In general, antibiotic use has not been markedly associated with the onset of prostate cancer (PCa). In fact, the use of antibiotics and anti-inflammatory drugs for prostate infection or prostatitis may offer some protection against PCa, which has been linked with prostate inflammation as a possible catalyst for PCa. (FYI, chronic inflammation in the body has also been linked with developing almost any cancer in the body.) However, in addressing repeated exposure to antibiotics and cancer, Boursi et al. (2015) write that PCa risk “increased modestly with the [recurrent] use of penicillin, quinolones, sulphonamides and tetracyclines.”^[iii]

The bottom line is: don’t take antibiotics unless they are absolutely necessary to treat bacterial infection, or to prevent infection during certain medical procedures. And remember: antibiotics are not effective against viruses! If you’re curious about the difference between bacteria and viruses, learn more here.

NOTE: This content is solely for purposes of information and does not substitute for diagnostic or medical advice. Talk to your doctor if you are experiencing pelvic pain, or have any other health concerns or questions of a personal medical nature.

[i] Akimoto N, Ugai T, Zhong R, Hamada T et al. Rising incidence of early-onset colorectal cancer – a call to action. Nat Rev Clin Oncol. 2021 Apr;18(4):230-243. Full article available at https://cpb-us-w2.wpmucdn.com/sites.wustl.edu/dist/f/1133/files/2020/12/10.1038@s41571-020-00445-1.pdf
[ii] Siegel, R. L. et al. Colorectal cancer incidence patterns in the United States, 1974–2013. J. Natl Cancer Inst. 109, djw322 (2017)
[iii] Boursi B, Mamtani R, Haynes K, Yang Y. Recurrent antibiotic exposure may promote cancer formation – another step in understanding the role of the human microbiota? Eur J Cancer. 2015 Nov; 51(17): 2655–2664.