Fluorouracil

Fluorouracil is an antimetabolite chemotherapy medicine used to treat breast cancer. It is one of the most commonly used medicines to treat cancer. Fluorouracil is also known as 5-fluorouracil and 5-FU.

How fluorouracil works

Fluorouracil interferes with the normal growth process of cancer cells. It stops them from making and fixing DNA, the directions that cells use to grow. Fluorouracil causes the cells to die when they try to divide. It works at specific times in the growth of the cell.

Who gets fluorouracil

Fluorouracil may be used in chemotherapy treatment regimens for invasive breast cancer, including triple-negative breast cancer.

It can be used to treat any stage of breast cancer, including metastatic disease.

How fluorouracil is given

Fluorouracil is given with other chemotherapy medicines in breast cancer. Some common combinations in breast cancer include:

• CAF (Cytoxan, Adriamycin and Fluorouracil) or FAC (Fluorouracil, Adriamycin, and Cyclophosphamide)
• CEF (Cytoxan, Epirubicin and Fluorouracil) or FEC
• CMF (Cytoxan, Methotrexate and Fluorouracil)

Fluorouracil is given by vein. It is usually given in several cycles, with a day (or days) of treatment followed by a period of “off” days. The exact schedule depends on the medicines used. Most chemotherapy regimens consist of between four and six cycles of treatment given over 3 to 6 months.

Side effects and things to remember

Side effects may include:

• Anemia
• Loss of appetite
• Diarrhea
• Fatigue
• Hand and foot syndrome
• Menopausal symptoms
• Mouth sores
• Nausea and vomiting
• Drop in white blood cells
• Taste changes
• Vision or eye problems

Before starting fluorouracil, tell your doctor about any medicines you are taking, including vitamins, herbal supplements and over-the-counter medicines. You should not take fluorouracil during the first trimester of pregnancy.

Your doctor will test your blood before and during treatment to check your white and red blood cell levels. Your liver and kidneys will also be checked.

Be sure to call your doctor right away if:

• You have chest pain, as this may be a sign of heart problems
• You have pain at the injection site, as this can be a sign of an allergic reaction
• You have a high fever, as this can be a sign of a serious infection

Your doctor, pharmacist or nurse can help you manage your side effects. You can also go to our section on Side effects for more information.

Fluorouracil and DPD deficiency

If you and your doctor are discussing fluorouracil as a potential treatment, it is important to know about a rare inherited genetic condition called DPD deficiency. Research shows that it’s rare to have complete DPD deficiency, which happens in fewer than 0.1% of people. Partial DPD deficiency occurs in about 6.8-11.5% of people.

People with any level of DPD deficiency were born with an inherited mutation in the DYPD gene. This mutation reduces the amount of DPD enzyme in the body. The DPD enzyme helps break down certain substances, including the chemotherapies capecitabine and fluorouracil.

People with DPD deficiency may be at risk for very serious reactions, including death, while taking capecitabine or fluorouracil. If you are considering either of these treatments, talk with your care team about DPD deficiency. Ask your team:

• If you should have inherited DYPD mutation testing
• How you can manage your individual risk for adverse effects while taking this medicine
• If there are other chemotherapy options