Glossary of medical terms

    Adjuvant treatment

    Treatment given after surgery to kill any cancer cells left behind after surgery.

    Cancer cell

    A cell that divides and reproduces abnormally with uncontrolled growth. This cell can break away, travel to other parts of the body, and then set up at another site. This process is referred to as metastasis.


    A type of medication that kills cells that grow and divide rapidly, including cancer cells and normal cells.

    Early breast cancer

    When the cancer is located in only the breast or is in the breast and has only spread to nearby lymph nodes, but not to other parts of the body.

    First-line therapy

    A treatment that is given first or as an initial treatment for cancer that is advanced or metastatic.

    HER2 receptor

    A type of protein that is found on the surface of cells in everyone. This protein tells cells to grow and divide. Too much HER2 is called “HER2 overexpression” and may result in the cells growing and dividing more quickly.

    HER2-positive (HER2+)

    HER2 stands for human epidermal growth factor receptor 2. When breast cancer cells have too many HER2 receptors, they are called HER2-positive, or HER2+ breast cancer.

    HER2-targeted therapies

    A type of targeted cancer treatment that binds to HER2 receptors to fight cancer cells that have too many HER2 receptors.

    Hormone receptor

    A protein on the edge or inside of cells to which hormones attach.


    A protein naturally found in most tissues of the body. In medicine, hyaluronidase is made in the laboratory and given with other drugs by injection under the skin to treat certain conditions. Hyaluronidase helps make the fluids and connective tissue thinner so the drugs can move more easily into the tissues.

    IV (intravenous)

    A method of administering a drug by inserting a needle into a vein. 


    A method of putting fluids, including drugs, into the bloodstream. Also called intravenous infusion.

    Lymph nodes

    Small, bean-shaped organs found throughout the body that store white blood cells and help remove cell waste, germs, and other harmful substances from the body.

    Metastatic breast cancer

    Breast cancer that has spread outside the breast to other parts of the body, such as the lungs, liver, or bones.

    Neoadjuvant treatment

    Treatment given before surgery to help reduce or get rid of cancer cells before surgery.

    Pharmacokinetics (PK)

    How a drug behaves in the body, including the amount that's absorbed into the bloodstream, how it is carried through the body, and how it is released from the body.


    A surgically implanted disc through which blood can be taken and medication can be given without repeated needle sticks; also called a “port-a-cath.”

    Targeted cancer treatment

    A type of medication that targets specific characteristics of cancer cells.


    An abnormal mass or growth of tissue that occurs when cells divide too rapidly in an uncontrolled way. Tumors that are malignant are known as cancer.

Important Safety Information & Uses

What does PHESGO treat?

PHESGO® (pertuzumab, trastuzumab, and hyaluronidase-zzxf) is a prescription medicine approved for use in combination with chemotherapy for:

  • use prior to surgery (neoadjuvant treatment) in adults with HER2-positive, locally advanced, inflammatory, or early stage breast cancer (tumor is greater than 2 cm in diameter or node-positive). PHESGO should be used as part of a complete treatment regimen for early breast cancer. 
  • use after surgery (adjuvant treatment) in adults with HER2-positive early breast cancer that has a high likelihood of coming back.

PHESGO is a prescription medicine approved for use in combination with docetaxel in adults who have HER2-positive breast cancer that has spread to different parts of the body (metastatic) and who have not received anti-HER2 therapy or chemotherapy for metastatic breast cancer.

What are the most serious side effects of PHESGO?

PHESGO may cause heart problems, including those without symptoms (such as reduced heart function) and those with symptoms (such as congestive heart failure).

  • The risk for and seriousness of these heart problems are highest in people who received both PHESGO and a certain type of chemotherapy (anthracycline)
  • Your doctor will check for signs of heart problems before, during, and after treatment with PHESGO. Based on test results, your doctor may hold or discontinue treatment with PHESGO
  • Contact a healthcare professional immediately for any of the following: new onset or worsening shortness of breath, cough, swelling of the ankles/legs, swelling of the face, palpitations, weight gain of more than 5 pounds in 24 hours, dizziness or loss of consciousness

Receiving PHESGO during pregnancy can result in the death of an unborn baby and birth defects.

  • Birth control should be used while receiving PHESGO and for 7 months after your last dose of PHESGO. If you are a mother who is breastfeeding, you should talk with your doctor about either stopping breastfeeding or stopping PHESGO
  • If you think you may be pregnant, you should contact your healthcare provider immediately
  • If you are exposed to PHESGO during pregnancy, or become pregnant while receiving PHESGO or within 7 months following the last dose of PHESGO, you are encouraged to report PHESGO exposure to Genentech at 1-888-835-2555

PHESGO may cause serious lung problems.

  • Your doctor may check for signs of lung problems including:
    • Severe shortness of breath
    • Fluid in or around the lungs
    • Weakening of the valve between the heart and the lungs
    • Not enough oxygen in the body
    • Swelling of the lungs
    • Scarring of the lungs

Who should not receive PHESGO?

  • PHESGO should not be used in patients who are allergic to pertuzumab, trastuzumab, hyaluronidase, or to any of the ingredients in PHESGO

What are other possible serious side effects?

  • PHESGO may worsen low white blood cell counts caused by chemotherapy: Low white blood cell counts can be life threatening and were seen more often in patients receiving Herceptin® (trastuzumab) plus chemotherapy than in patients receiving chemotherapy alone. Your doctor may check for signs of low white blood cell counts when he or she examines you
  • PHESGO may cause administration-related reactions: PHESGO is given as an injection. The active ingredients in PHESGO have been associated with severe administration reactions, including hypersensitivity or anaphylaxis, which can be fatal. Talk to your doctor if you feel any symptoms. The most common symptoms include dizziness, nausea, chills, fever, vomiting, diarrhea, hives, swelling of the skin, breathing problems, or chest pain

What are the most common side effects?

The most common side effects of PHESGO when given with chemotherapy as part of an early breast cancer regimen are:

  • Hair Loss
  • Nausea
  • Diarrhea
  • Low levels of red blood cells
  • Weakness

The most common side effects of PHESGO when given with docetaxel for treatment of breast cancer that has spread to other parts of the body (metastatic) are:

  • Diarrhea
  • Hair loss
  • Low levels of white blood cells with or without fever
  • Nausea
  • Feeling tired
  • Rash
  • Damage to the nerves (numbness, tingling, pain in hands/feet)

What should I know about side effects with PHESGO?

  • Not all people have serious side effects; however, side effects with PHESGO therapy are common. It is important to know what side effects may happen and what symptoms you should watch for
  • Your doctor may stop treatment if serious side effects happen. Be sure to contact your healthcare team right away if you have questions or are worried about any side effects

You are encouraged to report side effects to Genentech and the FDA. You may report side effects to the FDA at 1-800-FDA-1088 or You may also report side effects to Genentech at 1-888-835-2555.

Talk to a healthcare professional for more information about the benefits and risks of PHESGO. 

Please see full Prescribing Information for additional Important Safety Information, including most serious side effects.

If you cannot afford your medication, visit for financial assistance information.