The Use of Cytoxan (Cyclophosphamide) in Breast Cancer Treatment

A common chemotherapy drug

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Nurse cleaning out chemotherapy infusion port
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Cytoxan (cyclophosphamide) is a common chemotherapy drug that is used in combination with other medications to treat breast cancer and several other forms of cancer.


Cytoxan is typically used:

  • After surgery for early-stage breast cancer to reduce the risk of recurrence
  • Before surgery to shrink advanced-stage tumors
  • After surgery to treat advanced-stage tumors

This drug is also used to treat breast and ovarian cancers, lymphoma, leukemias, multiple myeloma, mycosis fungoides, neuroblastoma, and retinoblastoma.


Cytoxan works on cancer cells by damaging their DNA in a way that prevents them from dividing and kills them. This drug will also affect normal cells but will have less effect on them since they divide more slowly and are better able to repair their DNA than cancer cells.

Some of your normal cells that may be affected include blood, mouth tissue, digestive tract, and hair follicles.

Cytoxan is often combined with one other drug, Adriamycin, in a chemotherapy infusion to treat breast cancer. This combination is called AC. In rare instances, these drugs may also be combined with fluorouracil and called FAC or CAF.

Another chemotherapy combination used for breast cancer is Taxotere and Cytoxan. There also is a very old but still commonly used mixture called CMF, which has Cytoxan, methotrexate, and 5-fluorouracil.

A study published in 2017 looked at the combination of Cytoxan and the drug docetaxel as neoadjuvant chemotherapy in HER2-negative primary breast cancer. Researchers found this combination was effective against triple-negative breast cancer but not against other forms.

Dosage and Administration

Cytoxan can be given either intravenously as a solution or by mouth in pill form. 

For IV Cytoxan, dosages and infusion frequency varies depending on multiple factors, including cancer type and weight.

For Cytoxan tablets, the dosage is also variable and based on cancer type, weight, other treatments you may be on, and how you've responded to other treatments.

Cytoxan tablets must be taken whole. Don't ever cut, crush, or chew them.

Risks and Side Effects

The risks and side effects of Cytoxan chemotherapy include: 

  • Allergic reactions (shortness of breath, swelling of feet or ankles, rash, swollen throat)
  • During pregnancy, potential harm to the baby
  • Possible infertility in the future
  • Neutropenia (low blood count that leads to a greater risk of infection)
  • Hair loss
  • Nausea
  • Vomiting
  • Diarrhea
  • Fatigue
  • Irritation in the mouth
  • Menstrual cycle interruptions
  • Brittle nails

To help prevent kidney and bladder infections, be sure to drink more fluids and urinate more often.

If you have any of these symptoms, you should call your doctor right away:

  • Fever of 100.5°F or higher
  • Painful or bloody urine
  • Black and sticky stools or bloody stools
  • Unusual bruises or bleeding
  • Persistent cough or pneumonia

If you're pregnant or become pregnant, talk to your doctor about alternatives to Cytoxan. Your doctor may recommend reliable contraception in order to prevent pregnancy while you're on this drug.

It's also recommended that you avoid alcohol or caffeine, as they can be very dehydrating for your body and can cause problems.

For pain relief, ibuprofen is considered safer alongside Cytoxan than aspirin.

Cytoxan significantly impacts your system, so it usually recommended that you don't get vaccinations while undergoing treatment. 

A Word From Verywell

When considering Cytoxan or any breast cancer treatments, it's important to weigh the risks against the benefits and make an informed decision. You oncologist can help guide you through this process.

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