Antibiotics Potentially Raise CRC Risk, Research Shows

The ESMO World Congress on Gastrointestinal Cancer 2021 took place from June 30-July 3, 2021. During the Congress, researchers discussed data and research in the gastrointestinal field. According to MedScape, one presentation (Abstract #SO-25) focused on the potential association between antibiotics and early-onset colorectal cancer (CRC), especially in younger individuals.


I’m sure that many of those reading this have, at some point, taken antibiotics. Generally, antibiotics are topical, oral, or intravenous drugs administered to combat bacterial infection. Antibiotics do not treat viral infections and thus are not prescribed for such. But could exposure to antibiotics increase the risk of additional health issues in the future?

For this particular study, researchers sourced data from 7,903 patients with CRC and 30,418 healthy control individuals. Of those with CRC, 5,281 had colon cancer and 2,622 had rectal cancer. Researchers wanted to achieve two goals. First, they wanted to understand whether antibiotic use increased the risk of developing colon cancer. As colon cancer rates have been rising over the past few decades, it is important to understand what risk factors contribute to this outside of obesity, poor nutrition / poor diet, and alcohol use. Next, researchers also wanted to determine whether antibiotics could increase the prevalence of colorectal cancer diagnoses by changing the gut microbiome.

Research Findings

Findings included:

  • In people under 50 years old, antibiotics exposure heightened the risk of colon cancer by 49%. Unfortunately, as many younger patients with colon cancer are not diagnosed in a timely fashion, these patients also have worse outcomes.
  • Only 5.6% of patients with CRC were diagnosed before age 50. While 45% of patients had been prescribed antibiotics, the increased risk of colon and rectal cancer was clearest in these patients diagnosed before age 50.
  • Younger patients are ineligible for bowel cancer screening and are often not evaluated for colorectal cancer at younger ages, even if showing symptoms.
  • Exposure to antibiotics between 1-15 days showed the largest link to colon cancer for younger patients, with smaller relationships for 16-60 days of exposure, and no relationship for over 60 days.

Although an association was discovered, researchers also caution against making a definitive link between antibiotics and colorectal cancer. However, moving forward, the researchers stress that antibiotics should be avoided unless genuinely needed.

Colorectal Cancer

Colorectal cancer may also be referred to as colon, rectal, or bowel cancer. This cancer, which often begins as benign polyps outside of the colon and in the large intestine, becomes malignant (cancerous) over time. Screening may find polyps so that they can be removed before they turn cancerous. Typically, risk factors for developing colorectal cancer include age, a family history of colorectal cancer, obesity, smoking, a high-fat and low-fiber diet, alcohol use, diabetes, prior radiation treatment, or being African-American. In early stages, many patients may not display symptoms. However, when symptoms appear, they include:

  • Fatigue
  • Unintended weight loss
  • General malaise
  • Overall weakness
  • Rectal bleeding
  • Bloody stool
  • Feeling that bowels do not completely empty
  • Diarrhea, constipation, or other changes in bowel habits
  • Abdominal discomfort (pain, gassiness, cramping)
  • Anemia (low red blood cell count)
  • Abdominal lump

Learn more about colorectal cancer.

Jessica Lynn

Jessica Lynn

Jessica Lynn has an educational background in writing and marketing. She firmly believes in the power of writing in amplifying voices, and looks forward to doing so for the rare disease community.

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