Breast Cancer Medical Oncology

A doctor talks to a patient in a relaxed, sunny clinic in the Knight Cancer Institute.
Our medical oncologists are experts in chemotherapy, hormone therapy and targeted therapy.

Chemotherapy, hormone therapy and targeted therapy

The medical oncologists at OHSU’s Knight Cancer Institute understand the importance of treating your whole system to stop cancer. Their care includes:

  • Coordinated treatment, with your medical oncologist working closely with the other doctors on your care team.
  • The latest targeted therapies.
  • Access to clinical trials for promising new therapies.
  • Evidence-based therapy adjusted to fit your needs and wishes.
  • When appropriate, testing to reveal the genetic activity of your cancer to help guide treatment decisions.

Why do we use these therapies?

For many patients, breast cancer is a “systemic” disease. That means your whole system, not just the area with the tumor, needs treatment to kill cancer cells. Medical oncology can target microscopic cancer cells circulating almost anywhere in your body.

Systemic treatment can give you the best chance of getting rid of your cancer and keeping it from spreading or coming back. Medical oncology can also shrink or slow tumors in patients with advanced breast cancer.

Our excellence

Our medical oncologists are fellowship-trained and have particular expertise in treating breast cancer patients.

Your medical oncologist will follow the latest standards of care but will also tailor treatments to your needs and wishes.

The doctors at the Knight Cancer Institute are also scientists researching new ways to treat breast cancer. This includes clinical trials for promising new medications.

We’re consistently ranked among the top cancer hospitals in the nation by U.S. News and World Report.


Chemotherapy, or chemo for short, uses medications to kill cancer cells. Because chemo circulates in the bloodstream, it can kill breast cancer cells nearly anywhere in the body.

Chemotherapy used to be standard treatment for many patients. Now doctors can use genomic testing  analysis to reveal a tumor’s genetic activity to identify some of the patients who won’t benefit, sparing them from side effects. Genomic testing can also indicate how likely a cancer is to come back.

For now, results of genomic testing are reliable only for patients with some forms of early-stage breast cancer. Your medical oncologist will talk with you about whether genomic testing makes sense for you and, if so, how the results can guide treatment decisions. Read more below.

Chemotherapy targets fast-dividing cells, a key trait of cancer cells. Different medications work in different ways. Some chemo medications prevent the cells from dividing, for example, and others trigger them to self-destruct.

Most chemo patients receive a combination of medications, called a regimen, to target cancer from different angles.

Most often, chemo medications are given in an IV drip called an infusion. Patients often receive chemo on an outpatient basis in two- or three-week cycles, with time off to recover. The number of cycles depends on the treatment regimen.

Some patients have a port, a small device implanted in the chest and connected to a large vein. This enables them to receive chemo or have blood drawn without the nurse hunting for a vein. The port is removed when it’s no longer needed.

Neoadjuvant chemotherapy: This chemotherapy is given before surgery to shrink the tumor. This can reduce the extent of surgery or shrink a tumor that’s too big to remove surgically. Neoadjuvant chemo can also help your doctor identify which medications work best on your cancer.

Adjuvant chemotherapy: This chemotherapy is given after surgery to kill any cancer cells that may remain. Adjuvant chemo can lower the risk that cancer will come back or spread to another part of your body.

For advanced cancer: For patients with breast cancer that has spread outside the breast and underarm lymph nodes (also called metastatic breast cancer), chemotherapy may be given to shrink or slow the growth of tumors or to control symptoms.

Hormone therapy

Hormone therapy harnesses cancer cell “receptors” to keep cancer from growing and spreading. Receptors are proteins on the surface of cancer cells that “bind,” or attach, to hormones and medications.

Your cancer cells will be analyzed for receptors, most often using tissue from a biopsy. Read more about hormone receptors on the Understanding Breast Cancer page.

Hormone therapy can be effective if your cancer has receptors for the hormones estrogen and/or progesterone. If so, your cancer will be described as:

  • Hormone receptor positive or
  • Estrogen receptor positive and/or
  • Progesterone receptor positive

If you don’t have any hormone receptors, hormone therapy won’t work. Hormone therapy is most often given to three types of hormone-receptor-positive patients:

  • Those with early-stage cancer, to reduce the risk of cancer coming back.
  • Those with advanced (metastatic) cancer to shrink or slow tumor growth.
  • Those at high risk of breast cancer but not diagnosed, to lower their risk.

Hormone therapy is also sometimes used to shrink a tumor before surgery. 

Estrogen circulating in the body can bind to breast cancer cell receptors, like keys fitting in locks, and tell the cells to divide and grow. Most hormone therapies work by blocking the receptors — like jamming the lock to keep estrogen out — or by lowering the amount of estrogen in the body.

Most types are daily pills taken for five or more years. A type called "ovarian ablation" for premenopausal women uses surgery or injected medication. Patients with advanced or recurrent hormone-positive cancer sometimes receive monthly injections. 

Receptor blocking: This type works by binding to receptors, keeping out estrogen. Medications include tamoxifen, taken as a daily pill or liquid (brand names Nolvadex and Soltamox).

Estrogen blocking: This type targets the body’s ability to make estrogen by blocking a needed enzyme called aromatase. Medications called aromatase inhibitors are taken as daily pills. They are: anastrozole (brand name Arimidex), letrozole (Femara) and exemestane (Aromasin).

Ovarian disrupting: In premenopausal women, most estrogen comes from the ovaries. A hormone therapy called ovarian ablation can shut down estrogen production. The ovaries can be surgically removed or disabled temporarily with injected medications.

When it’s given: Like chemotherapy, hormone therapy can also be:

  • Neoadjuvant, to shrink the tumor before surgery. This is less common with hormone therapy than other therapies.
  • Adjuvant, to lower the risk of cancer returning.
  • For advanced cancer, to slow growth.

Targeted therapy

This type of therapy uses medication that affects specific molecules, or targets, in the cancer cells. This makes it less likely to affect normal cells, generally resulting in fewer side effects.

Targeted therapies for breast cancer are available for two types of patients:

  • Those whose cancer is HER2 positive, meaning their cancer cells have proteins, or receptors, that promote cancer growth. Read more about HER2 receptors on the Understanding Breast Cancer page.
  • Those with hormone-receptor-positive breast cancer.

Different medications target different pathways. Trastuzumab (Herceptin), for example, binds to HER2 receptors to prevent them from receiving signals to grow and multiply. Other medications help hormone therapies work better by disrupting cancer cell functions.

Most medications that target HER2 receptors are given by IV. Early-stage patients who receive adjuvant Herceptin, for example, receive weekly infusions for a year.

Medications for hormone-receptor-positive patients are daily pills and are generally used in combination with hormone therapy.

HER2 medications: These medications generally take advantage of HER2 receptors, either by blocking them so cancer cells can’t receive instructions to divide and grow, or by using them to deliver instructions that disrupt cell functions. IV medications include Herceptin, pertuzumab (brand name Perjeta) and ado-trastuzumab emtansine (Kadcyla). Another type, a daily pill called lapatinib (Tykerb), has small molecules that enter cancer cells to disrupt cell functions.   

Hormone receptor positive medications: Medications that help hormone therapies work better do so by inhibiting cancer cell functions. Palbociclib (Ibrance), for example, is a CDK 4/6 inhibitor that disrupts a protein that controls cell growth and division. Everolimus (Afinitor) is an mTOR inhibitor that targets a protein that controls cell growth and survival.

When it’s given: Targeted therapies can also be:

  • Neoadjuvant, to shrink the tumor.
  • Adjuvant, to lower the risk of cancer returning.
  • For advanced cancer, to slow growth.

Genomic testing

Genomic testing involves analyzing the activity of genes in your tumor to see:

  • If chemotherapy would be effective against your cancer.
  • If you are at low risk or high risk of your cancer coming back.

Testing results help doctors decide which patients need chemotherapy and which can safely avoid it. Results can also guide decisions about how aggressive your treatment needs to be to keep cancer from returning.

Genomic testing isn't appropriate for all patients. One common type, for example, has been found reliable only for women with early-stage, hormone-receptor-positive, HER2-negative breast cancer. 

It's also important to note that genomic testing is not the same as genetic testing.

  • Genomic testing looks at the activity of genes in breast cancer tissue.
  • Genetic testing looks to see if you inherited a harmful mutation in certain genes, such as BRCA1 or BRCA2, that put you at high risk of developing breast cancer.

Clinical trials

The Knight Cancer Institute is on the leading edge of clinical trials for therapies to treat breast cancer, including new targeted medications. Your care team will talk with you about whether a trial is right for you.

The Knight Cancer Institute is also among the world’s leaders in targeted therapy. Director Brian Druker, M.D., helped pioneer Gleevec, a breakthrough medication for chronic myeloid leukemia that first demonstrated the power of targeted cancer medicine.

Side effects

Though treatment with medical oncology can come with many potential side effects, your care team will work with you to limit and manage them.

Our rehabilitation services program offers a full range of therapies to treat physical and cognitive issues, and our social workers can help with emotional and other issues.

Common side effects include:

  • Bone loss
  • Diarrhea
  • Fatigue
  • Foggy thinking and memory loss (“chemo brain")
  • Hair loss
  • Hot flashes
  • Joint pain
  • Mouth sores
  • Nausea
  • Neuropathy (pain, weakness and numbness, usually in the hands and feet)
  • Vaginal dryness

Learn more

For patients

Call 503-494-4673 to:

  • Make an appointment
  • Seek a second opinion
  • Ask questions


Knight Cancer Institute, South Waterfront

Center for Health & Healing Building 2
3485 S. Bond Ave.
Portland, OR 97239

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