Colon cancer data reinforce need to reduce unnecessary antibiotic use

New findings from a study presented at the European Society for Medical Oncology (ESMO) World Congress on Gastrointestinal Cancer 2021 (30 June – 3 July) suggest that excessive antibiotic use may increase the risk of colon cancer, particularly among people below the age of 50[1]. The study draws attention to the estimated 65% increase in global antibiotic consumption that was reported between 2000-2015[2] and the association with colon cancer development.

The Scottish study used a large database containing primary care health information of up to 2 million people to investigate the association between antibiotics use and risk of developing colon cancer. Among the 8000 people with colon cancer, the investigators found that antibiotic use was linked to an increased risk of colon cancer across all ages, though the risk was increased by almost 50% in people under 50 compared to 9% in people over 50 years. Furthermore, among younger patients, antibiotic use was associated with cancers in the right colon. Cancer that originates in the right colon (ascending colon, hepatic flexure and transverse colon) tends to have poorer prognoses and clinical outcomes compared to cancer originating in the left colon (half of the transverse colon, splenic flexure, descending colon, and sigmoid colon)[3]. Quinolones, such as ciprofloxacin (Cipro) and sulfonamides/trimethoprim antibiotics, which are used to treat a range of infections, were associated with right-sided colon cancer.

The investigators note that the bacteria that inhabit the right colon may be very different from the bacteria that inhabit other sections of the colon. The totality of microorganisms that inhabit our digestive tract – the microbiome – is under close study to determine whether there is a link between antibiotic use and changes in the microorganism populations that can increase the risk of colon cancer.

While it remains unknown whether excessive antibiotic use directly causes colon cancer, these findings show an association that highlights the importance of reducing unnecessary antibiotic use. The possibility that excessive antibiotic use may be exposing people to a higher risk of cancer cannot be ignored.

 Take away message:

Findings from a recent study found that excessive antibiotic use is linked to an increased risk of colon cancer across all ages, with an alarming 50% increase in risk of colorectal cancer in people under 50.

[1] Bowel cancer data reinforce need to reduce unnecessary antibiotic use. 2 Jul 2021. Retrieved from: https://www.esmo.org/newsroom/press-office/bowel-cancer-data-reinforce-need-to-reduce-unnecessary-antibiotic-use

[2] Klein EY et al. Global increase and geographic convergence in antibiotic consumption between 2000 and 2015. Proc Natl Acad Sci U S A 2018 Apr 10; 115:E3463. (https://doi.org/10.1073/pnas.1717295115)

[3]Baran B et al. Difference between left-sided and right-sided colorectal cancer: a focused review of literature. Gastroenterology Res. 2018 Aug; 11(4): 264-273. Published online 2018 Feb 8. doi: 10.14740/gr1062w