Cytoxan (Cyclophosphamide) for Breast Cancer Treatment

A common chemotherapy drug

Cytoxan (cyclophosphamide) is a common chemotherapy drug that prevents cancer cell division and cancer growth. It is used in combination with other medications to treat breast cancer and several other forms of cancer. When considering Cytoxan or any breast cancer treatments, it's important to weigh the risks against the benefits and make an informed decision. Your oncologist can help guide you through this process.

Nurse cleaning out chemotherapy infusion port
Mark Harmel/Photographer's Choice/Getty Images


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 ovarian cancer, lymphoma, leukemia, multiple myeloma, mycosis fungoides, neuroblastoma, and retinoblastoma.

How It Works

Cytoxan treats cancer by damaging the cancer cell DNA in a way that prevents the cells from dividing and kills them. This drug will also affect healthy cells but will have less effect on most healthy cells because they divide more slowly.

Some of the healthy cells that may be affected by this drug include blood, digestive tissue, and hair follicle cells.

Drug Combinations

Cytoxan is often combined with 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.


The therapeutic effects of Cytoxan are not the same for all types of cancer, and research studies are used to determine which subtypes may benefit from various chemotherapy combinations.

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 other forms.

In another 2017 study, Cytoxan was used in a combination called ACTHP that had an 85% success rate in clearing cancer from axillary nodes in HER2-positive early-stage cancer.

The other drugs in the combination were:

  • Doxorubicin
  • Trastuzumab
  • Pertuzumab

Research published in Clinical Cancer Research suggested that the molecular subtype luminal A breast cancer didn't benefit at all from adjuvant chemotherapy with Cytoxan.

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 body 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)
  • Potential harm to a fetus
  • Possible infertility
  • 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

If you have any of these symptoms, call your healthcare provider right away:

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

Your healthcare provider may recommend reliable contraception in order to prevent pregnancy while you're on this drug. If you're pregnant or become pregnant, tell your healthcare provider right away.

To help prevent kidney and bladder infections, be sure to drink plenty of fluids so that you will urinate often. It's also recommended that you avoid alcohol and caffeine, as they can be very dehydrating for your body and exacerbate some of the effects of Cytoxan.

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

Cytoxan significantly impacts the immune system, so getting vaccinations is usually not recommended while you're undergoing treatment.

11 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  3. Taxotere and Adriamycin/Cytoxan (AC) Validation in Breast Cancer Patients. Full Text View. Taxotere and Adriamycin/Cytoxan (AC) Validation in Breast Cancer Patients - Full Text View -

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  5. Malhotra V, Dorr VJ, Lyss AP, et al. Neoadjuvant and adjuvant chemotherapy with doxorubicin and docetaxel in locally advanced breast cancer. Clin Breast Cancer. 2004;5(5):377-84. doi:10.3816/cbc.2004.n.045

  6. Singh JC, Mamtani A, Barrio A, et al. Pathologic complete response with neoadjuvant doxorubicin and cyclophosphamide followed by paclitaxel with trastuzumab and pertuzumab in patients with HER2-positive early stage breast cancer: A single center experienceOncologist. 2017 Feb;22(2):139-143. doi:10.1634/theoncologist.2016-0268

  7. Singh JC, Mamtani A, Barrio A, et al. Pathologic Complete Response with Neoadjuvant Doxorubicin and Cyclophosphamide Followed by Paclitaxel with Trastuzumab and Pertuzumab in Patients with HER2-Positive Early Stage Breast Cancer: A Single Center Experience. Oncologist. 2017;22(2):139-143. doi:10.1634/theoncologist.2016-0268

  8. Nielsen TO, Jensen MB, Burugu S, et al. High-risk premenopausal Luminal A breast cancer patients derive no benefit from adjuvant cyclophosphamide-based chemotherapy: Results from the DBCG77B clinical trialClin Cancer Res. 2017 Feb 15;23(4):946-953. doi:10.1158/1078-0432.CCR-16-1278

  9. CYCLOPHOSPHAMIDE. IARC Working Group on the Evaluation of Carcinogenic Risk to Humans. Pharmaceuticals. Lyon (FR): International Agency for Research on Cancer. (IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, No. 100A.)

  10. Wu KS, Kwok C, Lok A. Oral versus intravenous administration of cyclophosphamide: a case reportCases J. 2008;1(1):395. doi:10.1186/1757-1626-1-395

  11. Mcquade RM, Stojanovska V, Abalo R, Bornstein JC, Nurgali K. Chemotherapy-Induced Constipation and Diarrhea: Pathophysiology, Current and Emerging Treatments. Front Pharmacol. 2016;7:414. doi:10.3389/fphar.2016.00414

Additional Reading

By Pam Stephan
Pam Stephan is a breast cancer survivor.