Study details
Previous studies have demonstrated that, in older adults, significant alterations in the structure and diversity of the gut microbiome induced by antibiotic therapy influence the development of colorectal cancer.
However, Ms. Perrott said that the impact of antibiotic use on early onset colorectal cancer has not been investigated.
The researchers therefore conducted a nested case-control study of primary care records to identify colorectal cancer cases diagnosed in Scotland between 1999 and 2011.
Patients were divided into those diagnosed before 50 years of age and those diagnosed at 50 years and older and matched with up to five healthy controls.
The study included 7,903 CRC cases, of which 5,281 were colon cancer and 2,622 rectal cancer, alongside 30,418 controls.
Among the CRC patients, 445 (5.6%) were under 50 years of age at diagnosis.
The team also analyzed antibiotic use history. Prescriptions for oral antibiotics, stratified by drug class and by anaerobic/nonanaerobic effect, were extracted, and the total antibiotic exposure period was calculated and categorized as 0, 1-15, 16-60, and >60 days.
Overall, 45% of the patients were prescribed antibiotics. Any antibiotic use was associated with a significantly increased risk of colon cancer, but this was most pronounced in patients aged less than 50 years at diagnosis.
Specifically, any antibiotic use was associated with an adjusted odds ratio of colon cancer of 1.49 (P = .018) in patients aged less than 50 years versus 1.09 (P = .029) in those aged 50 years and over.
In younger patients, the largest association between antibiotic use and colon cancer was seen in patients with a total antibiotic exposure of 1-15 days (at an adjusted odds ratio of 1.55), falling to 1.46 with 16-60 days of exposure, and no association for >60 days exposure.
No such relationship was seen in patients with colon cancer aged 50 years and over at diagnosis.
There was also no significant relationship between any antibiotic use and the occurrence of rectal cancer, at an adjusted odds ratio of 1.17 (P = .493) in those aged under 50 years at diagnosis and 1.07 (P = .698) in older patients.
The study was supported by Cancer Research UK. Ms. Perrott, Dr. Sobrero, and Dr. Samuels declared having no conflicts of interest. Dr. Seufferlien has reported relationships with Amgen, Bayer, Merck, Sanofi, Celgene, Shire, Roche, Falk Foundation, AstraZeneca, Lilly, Merck-Serono, Servier, Pierre Fabre, Cantargia, and Boehringer Ingelheim.
A version of this article first appeared on Medscape.com.