Oral antibiotics tied to colon, but not rectal, cancer

  • Zhang J & al.
  • Gut
  • 19 Aug 2019

  • curated by Jim Kling
  • Univadis Clinical Summaries
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Takeaway

  • Exposure to oral antibiotics is associated with an increased risk for colon cancer and decreased risk for rectal cancer.

Why this matters

  • Effect may be a result of differential disruption of colonic microbiota.
  • More evidence that physicians should be judicious in prescribing antibiotics.

Study design

  • Case-control study: 28,980 cases and 137,077 matched control individuals from the Clinical Practice Research Datalink (United Kingdom).
  • Funding: Johns Hopkins, Bloomberg-Kimmel Institute for Cancer Immunotherapy.

Key results

  • Antibiotic use vs no use, colon cancer (Ptrend<.001 style="list-style-type:circle;">
  • 1-15 days: aOR, 1.08.
  • 16-30 days: aOR, 1.14.
  • 31-60 days: aOR, 1.15.
  • >60 days: aOR, 1.17.

  • Antibiotic use vs no use, proximal colon cancer (Ptrend=.046):
    • 1-15 days: aOR, 1.14.
    • 16-30 days: aOR, 1.15.
    • 31-60 days: aOR, 1.32.
    • >60 days: aOR, 1.09.

  • Significant interactions observed between antibiotic use and tumor location (colon vs rectum, P<.001 proximal vs distal colon p>=.019). 
  • Antianaerobic antibiotics were associated with increased colon cancer risk (Ptrend<.001 particularly in the proximal colon.>
  • Antibiotic use was inversely associated with rectal cancer risk, especially with >60 days of use (aOR, 0.85; Ptrend=.003).
  • Association was found with antibiotic use >10 years before diagnosis (aOR, 1.17 [95% CI, 1.06-1.31]).
  • Limitations

    • Cannot prove causation.