5-FU Toxicity

What is 5-FU (fluorouracil)?

5-FU (fluorouracil) is an anti-cancer (“antineoplastic” or “cytotoxic”) chemotherapy drug.  This medication is classified as an “antimetabolite.”

5-FU is used for several different types of cancers, including colon and rectal, breast, gastrointestinal (anal, esphageal, pancreas and stomach), head and neck, liver, and ovarian. In cancer of the skin, 5-FU is used topically (cream or solution).

Up to 30% of cancer patients receiving 5-FU experience severe toxicity (grades 3 and 4).

Signs of 5-FU Toxicity

Common side effects of 5-FU, which occur in greater than 30% of patients taking 5-FU are:

  • Diarrhea
  • Nausea and vomiting
  • Mouth sores
  • Poor appetite
  • Watery eyes, sensitivity to light
  • Changes in taste
  • Discoloration along the vein through which the medication is given
  • Low white/red blood cells and platelets

Less common side effects of 5-FU, occurring in about 10-29% of patients are:

  • Dry, cracking, peeling and/or darkening of the skin
  • Thinning hair
  • Discoloration or loss of nails
  • Hand-foot syndrome: skin rash, swelling, redness, pain, peeling of the skin on the palms of hands or soles of feet

Serious side effects of 5-FU are:

  • Memory loss
  • Chest pain
  • EKG changes
  • Increase in cardiac enzymes (may indicate problems with the heart) 

Risks related to DPD Deficiency

Patients with full or partial DPD Deficiency may experience some or all of these symptoms and are at serious risk of neuroencephalopathy (brain damage) and death.

At the moment, people having 5-FU (fluorouracil) or capecitabine do not have routine testing for DPD Deficiency before their treatment. Your doctor can arrange a blood test if you have 5-FU (fluorouracil) or capecitabine and have severe side effects, but this may be too late. You should insist on a test being done BEFORE your treatment begins.

A potential sign of DPD Deficiency is consistently having high levels of thymine or uracil in your blood, since the enzyme needed to process these is absent from your body. This could be the first indication that there is a potential risk for DPD Deficiency and further blood tests before chemotherapy could prevent severe 5-FU toxicity.

Pre-testing for DPD Deficiency is HIGHLY recommended before treatment with 5-FU (fluorouracil). MedScape talks about testing facilities on their website.

Learn more about DPD Deficiency at www.dpd-deficiency.com.

Learn more about the risks of 5-FU based chemotherapy at www.know-the-risk-of-5fu-chemotherapy.com