Breast cancer treatments

This page was reviewed under our medical and editorial policy by

Daniel Liu, MD, Plastic and Reconstructive Surgeon

This page was updated on May 5, 2022.

“You have breast cancer.” The words may still resound in your head, and now you’re expected to make decisions about your treatment. This is a lot to process all at once—and may no doubt be overwhelming.

Take heart in knowing, however, that thanks to continuing medical advances, cancers are being detected earlier through regular breast cancer screenings, and are often caught in their most treatable stages. Cancer care teams are also getting better at treating breast cancer in all its stages.

Who treats breast cancer?

Breast cancer is a complex disease that requires a team of experts who not only treat the cancer but who also help you manage its symptoms and side effects. At City of Hope, your care team may include one or more of the following physicians:

Medical oncologist: Your cancer care team will be led by a medical oncologist. This doctor diagnoses and treats cancer, usually with chemotherapy, targeted therapy, immunotherapy and other drugs. A medical oncologist also coordinates with other members of your care team, including oncologists who are experts in other aspects of cancer care, such as surgery or radiation therapy.

Breast surgeon: This surgeon is a type of surgical oncologist who specializes in operations on the breast. A breast surgeon may perform a variety of surgeries to treat cancer, including biopsies, lumpectomies and mastectomies.

Radiation oncologist: This doctor uses radiation therapy to treat cancer. Radiation oncologists may use one or a combination of radiation therapy technologies to treat breast cancer. Radiation therapy for breast cancer is used to kill remaining cancer cells after a tumor has been removed.

Plastic surgeon: This surgeon reconstructs the breast after a mastectomy or lumpectomy. Also called reconstructive surgeons, these doctors may perform these reconstructive procedures either immediately after surgery to remove a tumor, or later, depending on a variety of factors.

Pathologist: This doctor helps diagnose cancer by analyzing samples removed from the patient’s breast or lymph nodes. Pathologists may examine blood samples or tissue taken during a biopsy to determine whether the patient has cancer, and if so, will determine the stage of the cancer.

When making decisions about your breast cancer treatment options, your team will consider several important factors, including:

  • The stage of your breast cancer and whether it’s spread to lymph nodes or other areas such as the bones, liver or brain
  • The hormonal status of the cancer: Is it estrogen receptor-positive (ER-positive) or progesterone receptor-positive (PR-positive)? 
  • The presence of the human epidermal growth factor receptor 2 (HER2) protein
  • Your age and menopausal status
  • Your overall health, well-being and preferences
  • The presence of genomic markers, including mutated copies of the breast cancer genes BRCA1 and BRCA2 (Certain tests such as Oncotype DX®, MammaPrint® and Prosigna® also detect other breast cancer genes.)


Surgery is a common part of a treatment plan for breast cancer patients. The type you have depends on many factors and the shared decision you make with your cancer care team. 

Surgical procedures are designed to remove cancerous cells from your body, and they may sometimes be used to help doctors see whether cancer has spread.

Most often, the goal of surgery in treating breast cancer is to remove the entire tumor from the breast—or as much as possible. The two main types of surgery to remove breast cancer are:

Lumpectomy (also called breast-conserving surgery, partial mastectomy or wide excision) is designed to remove all the cancer from the breast, while leaving intact breast tissue that’s not cancerous. Only the tumor—and a bit of normal tissue that surrounds it—is taken out.  

Mastectomy is a surgery that removes the entire breast. Some women have both breasts removed—in a procedure called a double mastectomy.

Learn more about breast cancer surgeries

Side effects of breast cancer surgery

Surgery for breast cancer may result in side effects that require additional medical treatment and supportive care services.

Side effects may include:

  • Bleeding
  • Infection
  • Pain, tightness
  • Reduced shoulder and chest mobility
  • Seroma, a build-up of fluid around a scar in in the armpit
  • Lymphedema, a collection of lymph fluid that may cause swelling and discomfort
  • Fatigue brought on by stress and the emotional toll of the surgery


Chemotherapy may be recommended before breast cancer surgery (neoadjuvant) or after surgery (adjuvant):

Neoadjuvant (or primary systemic) breast cancer chemotherapy is used before surgery to reduce the size of large breast tumors and to destroy cancer cells. This type of chemotherapy often makes breast-conserving surgery possible. It also helps cancer doctors determine the effect a particular regimen is having on the breast tumor.

Adjuvant breast cancer chemotherapy is used after surgery or radiation therapy to eliminate any remaining cancer cells that may not have been removed during breast cancer surgery and/or radiation therapy. It also may prevent the disease from spreading to other parts of the body.

Before chemotherapy, solid tumors may undergo genomic testing to determine whether they are likely to respond to specific chemotherapeutic drugs, thereby avoiding unnecessary toxicity to you.

During chemotherapy for breast cancer, patients will be monitored and may receive physical exams, blood tests, computed tomography (CT) scans, magnetic resonance imagine (MRI) scans and X-rays.

Side effects of chemotherapy for breast cancer

Chemotherapy works by targeting fast-growing cancer cells. But it may also kill other cells in the body that grow quickly, such as those in hair follicles, bone marrow and the digestive system. As a result, chemotherapy for breast cancer may cause a variety of side effects, including:

  • Hair loss
  • Nausea and vomiting
  • Diarrhea or constipation
  • Suppressed immunity

Hormone therapy

Some breast cancers are fueled by the female hormones estrogen and progesterone. The cells need these hormones to keep growing and spreading. These breast cancers are called hormone receptor-positive because their cells contain receptors (a special type of protein) that are specifically designed to attach to hormones and stimulate the cancer’s growth. When no hormone receptors (or only a few) are present in breast cancer cells, the cancer is considered hormone receptor-negative.

Hormone therapy only works on breast cancers that are hormone receptor-positive, and most breast cancers are in this category. Hormone therapy drugs treat breast cancer by starving cancer cells of the hormones they need. 

The two most common types of breast cancer hormone therapy are:

Selective estrogen receptor modulators (SERMs): These drugs bind to estrogen receptors in the breast cancer cells to block estrogen from reaching cancer cells, preventing their growth. Tamoxifen is a commonly used hormone therapy designed to prevent breast cancer recurrence. This drug is also used for some women who are at high risk for developing breast cancer.

Aromatase inhibitors: These breast cancer hormone therapy drugs block estrogen production by binding to the enzyme responsible for producing estrogen (the aromatase enzyme). Once estrogen production is halted, the cancer cells starve from lack of estrogen, which prevents them from growing and dividing.

If you’re prescribed hormone therapy, you may need to take the drugs for an extended period—usually around five to 10 years. Completing the full course of treatment is important because it helps reduce the chance the cancer will return.

Side effects of hormone therapy for breast cancer

Hormone therapy may cause a variety of side effects, including:

  • Hot flashes
  • Irregular periods
  • Changes in mood
  • Reduced sex drive
  • Vaginal dryness and irritation
  • Vaginal discharge

Some hormone therapies may also cause joint and bone pain and increase the risk of bone loss and osteoporosis.

Radiation therapy

Radiation therapy for breast cancer destroys or slows the growth of cancer cells by targeting them with high-energy X-rays or other types of radiation, which is designed to damage their DNA. In combination with other therapies, radiation therapy is a common treatment option for patients with breast cancer.

Most often, radiation therapy is used after breast cancer surgery to kill off cancer cells that may have been left behind, either in the breast area or in nearby lymph nodes. It may also be used to help destroy cancer cells that have spread to other parts of the body, such as the bones or brain.

Breast cancer patients may already be dealing with an advanced-stage disease. Others have previously received traditional radiation therapy treatments and cannot tolerate more radiation exposure. There are technologies that allow doctors to re-treat previously treated areas where cancer has recurred, specific to the stage of the disease or previous treatment.

Side effects of radiation therapy for breast cancer

Some patients may experience side effects of radiation therapy weeks or months after the treatments begin. In many cases, side effects go away after treatment ends. But patients may experience fatigue for weeks, even months, after treatments are over.

Other side effects of radiation therapy for breast cancer include skin irritation and breast pain.

Learn more about radiation therapy for breast cancer

Targeted therapy

In addition to chemotherapy drugs, biological response drugs may be recommended to treat breast tumors that produce too much of, or over-express, a protein called HER2. If laboratory testing reveals the HER2 gene in the cancer cells, the medications may help shut down the HER2 gene, cutting the cancer cells off from their energy supply.

Breast cancer targeted therapy is commonly paired with other treatments, such as chemotherapy, to help control cancer that has spread or to prevent breast cancer recurrence.

Beyond HER2-positive breast cancers, targeted therapies may also be used to help treat:

There are many types of targeted therapies, each designed to treat specific cellular changes responsible for a certain kind of breast cancer. Some of the common types of targeted drugs used to treat breast cancer include:

The side effects of targeted therapy vary widely, from mild to severe, depending on the type of targeted drug and the type of breast cancer it targets. Nausea, vomiting and fatigue are three of the more common side effects of several targeted therapies, but some side effects may be more serious. For example, when used to treat HER2-positive breast cancers, monoclonal antibodies and antibody drug conjugates pose a risk of heart damage, while kinase inhibitors may cause severe diarrhea, liver problems and hand-foot syndrome. Most of the time, however, the side effects of targeted drugs are not dangerous and often resolve after the drug is stopped. Ask your doctor about the risks of a certain targeted drug and the side effects to watch out for.

Side effects of targeted therapy for breast cancer

The side effects of targeted therapy vary widely, from mild to severe, depending on the type of targeted drug and the type of breast cancer it targets.

Common side effects include:

  • Nausea
  • Vomiting
  • Diarrhea
  • Fatigue

Some targeted therapy drugs may cause serious side effects. For example, when used to treat HER2-positive breast cancers, monoclonal antibodies and antibody drug conjugates pose a risk of heart damage. Kinase inhibitors may cause severe diarrhea, liver problems and hand-foot syndrome.

In most cases, however, the side effects of targeted drugs are not dangerous and often resolve after the drug is stopped. Ask your doctor about the risks of a certain targeted drug and the side effects to watch out for.


Drugs known as checkpoint inhibitors may be an option to treat patients with breast cancers whose cells have specific genetic features.

The U.S. Food and Drug Administration (FDA) has approved the use of a checkpoint inhibitor in combination with a specific chemotherapy drug for patients with inoperable, advanced triple-negative breast cancer that expresses the protein receptor PD-L1. Checkpoint inhibitors work by blocking receptors, such as PD-L1, from interacting with compatible receptors on immune cells, preventing an immune response.

Immunotherapy may also be an option to treat patients with inoperable, metastatic breast cancer with one of two genetic features: microsatellite instability-high (MSI-H) or mismatch repair deficiency (dMMR). 

Clinical trials

Clinical trials are a key testing ground for determining the effectiveness and safety of new treatments and drugs for many diseases, including cancer. Your doctor may recommend that you consider enrolling in carefully selected breast cancer clinical trials, if you meet specific criteria, to offer you access to treatment options that would otherwise be unavailable to you.

Each patient is considered for a clinical trial on an individual basis and may qualify at any stage of disease or treatment. Talk to your doctor about whether a breast cancer clinical trial is a good option for you and ask about the risks and various requirements involved.

Breast cancer treatments by stage

The care team will create a treatment plan based on a variety of factors, including the cancer stage. Throughout treatment, the cancer will be monitored to evaluate whether treatment is working as planned. For instance, the care team may order a CA 15-3 test, which uses blood samples to track the progression of breast cancer and how it responds to treatment. When used in conjunction with additional tests, the care team can use this data to adjust treatments when necessary.

Stage 0 breast cancer

Stage 0 is the lowest-risk breast cancer stage. In this stage, breast cancer is detected before it spreads from the milk duct. Ductal carcinoma in situ (DCIS) is an example of stage 0 breast cancer.

Treatment may include surgery to remove the breast cancer, possibly followed by radiation or hormonal therapy if the cancer is hormone receptor-positive. Hormonal therapy may include tamoxifen or a type of drug known as an aromatase inhibitor, which is taken for five years after surgery to lower the risk of the breast cancer recurring.

The surgeon may remove just the tumor, via breast conservation surgery, or the entire breast, if the cancer is large or has been detected in several spots in the milk ducts.

Stage 1 breast cancer

If you have stage 1 breast cancer, the tumor is small and has not spread to your lymph nodes—or if it has, this spread has only just begun. 

Surgery is typically the first choice for stage 1 breast cancer, whether it’s breast conservation surgery or a mastectomy. Your doctor will likely remove lymph nodes during the surgery to prevent the spread of breast cancer cells. You may be able to opt for breast reconstruction after a mastectomy.

Your doctor also may suggest radiation in addition to the breast conservation surgery, to target cells that may have been left behind and to lower your chances of a recurrence. Radiation is usually not needed after a mastectomy in this stage. 

If your cancer is ER-positive or PR-positive, your doctor may recommend hormone therapy as well. It is typically taken for five years to lower the chances of your cancer reoccurring. If your breast cancer is HER2-positive, drugs that block this protein may be prescribed for up to one year.

Chemotherapy may also be an option if your tumor is larger than one cm (the size of a pea), growing quickly and/or is hormone receptor-negative, HER2-positive, and has other qualities suggesting it’s aggressive.

Stage 2 breast cancer

Stage 2 breast cancers are larger than stage 1 tumors, and the cancer cells have spread and have been found in a few nearby lymph nodes. 

If you are in stage 2, your cancer may be categorized as stage 2A or 2B. The secondary classification is based on the tumor’s size and spread. Treatment typically starts with breast-conserving surgery or a mastectomy. Your surgeon may remove some lymph nodes to examine the spread of the cancer cells. Radiation is often needed because the cancer has begun spreading to your lymph nodes. 

Your care team may recommend systemic therapies, such as chemotherapy, HER2 drugs or hormone therapy, before and/or after surgery. 

Pre-surgery treatments may help shrink a tumor enough that it may be removed through a breast conservation procedure.

Stage 3 breast cancer

Stage 3 breast cancers include tumors that measure more than 5 cm or about 2 inches, are growing into skin over the breast or the muscle underneath, or have infiltrated many nearby lymph nodes. 

At this point, despite its size, the stage 3 breast cancer hasn’t spread to other organs and may be sub-classified as stage 3A, 3B and 3C, based on size and degree of lymph node involvement.

Your care team may suggest chemotherapy as first-line treatment, with the goal of shrinking the tumor so it may be removed surgically, while sparing the rest of your breast. If the therapy doesn’t reduce enough of the cancer, though, you may need to undergo a mastectomy. In the event that your cancer is large and/or has infiltrated nearby tissues, your care team may suggest surgery first for stage 3 breast cancer.

After surgery, doctors may recommend radiation, as well as HER2 or hormone therapy drugs, depending on the cancer’s properties. 

Stage 4 breast cancer

Stage 4 means the breast cancer has spread to other organs or areas of the body, such as the brain, bones, lung and/or liver. In these cases, your team may recommend a systemic therapy such as hormone therapy or chemotherapy, or targeted drugs such as those that block HER2, immunotherapy or some combination of all these options. 

Your treatment plan may also include surgery and/or radiation. While this diagnosis may be scary, it’s important to know that your cancer care team has more tools to treat stage 4 breast cancer than ever before. Make sure to discuss all the options with your doctor. 

Learn more about breast cancer stages

Recurrent breast cancer

Despite best efforts and modern advances, sometimes breast cancer returns. If this occurs, your treatment will depend on where the cancer recurs, which treatments you’ve previously undergone and how you’ve responded to them.

Triple-negative breast cancer

Triple-negative breast cancers aren’t estrogen or progesterone receptor-positive, and they don’t produce too much HER2 protein. This is why they’re referred to as triple-negative breast cancers.  

Chemotherapy is the main systemic treatment for this type of cancer, because hormonal or HER2 targeted treatments aren’t known to work. Your care team may suggest immunotherapy (possibly with chemotherapy as well) if your tumor tests positive for PD-1 or PD-L1, a protein that’s found in immune cells. 

Inflammatory breast cancer

Inflammatory breast cancer is at least a stage 3 and grows quickly. It often causes changes to the skin of the breast. Treatment typically involves chemotherapy (and sometimes targeted therapy), then surgery. Radiation therapy may be another option, if other therapies haven’t worked as well to shrink the cancer before surgery. Radiation may also be used after surgery (if not used before) to improve the chances that the cancer won’t return. 

Targeted therapies are also often used after surgery to continue fighting hormone receptor-positive and HER2-positive cancers.

The future of breast cancer treatments

Every day brings new research aimed at better diagnosing and treating breast cancers and improving survival and quality of life. Studies are examining an array of gene mutations and additional receptors that may be involved in cancer growth. Researchers also are seeking drugs and supportive care options to help survivors avoid the side effects of treatments.

The goal is to better match treatments to specific cancers, by creating genomic profiles of tumors in an effort to reduce trial and error. Such personalized medicine is thought to be the future of cancer care. 

Next topic: How is breast cancer treated with radiation therapy?

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