Treatment of Breast Cancer Stages I-III

The stage (extent) of your breast cancer is an important factor in making decisions about your treatment. 

Most women with breast cancer in stages I, II, or III are treated with surgery, often followed by radiation therapy. Many women also get some kind of drug therapy. In general, the more the breast cancer has spread, the more treatment you will likely need. But your treatment options are affected by your personal preferences and other information about your breast cancer, such as:

  • If the cancer cells contain hormone receptors (that is, if the cancer is ER-positive or PR-positive)
  • If the cancer cells have large amounts of the HER2 protein (that is, if the cancer is HER2-positive)
  • Your overall health 

Talk with your doctor about how these factors can affect your treatment options.

Treating stage I breast cancer

These breast cancers are still relatively small and either have not spread to the lymph nodes or have spread to only a tiny area in the sentinel lymph node (the first lymph node to which cancer is likely to spread).


Surgery is the main treatment for stage I breast cancer. These cancers can be treated with either breast-conserving surgery (BCS; sometimes called lumpectomy or partial mastectomy) or mastectomy. The nearby lymph nodes will also need to be checked, either with a sentinel lymph node biopsy (SLNB) or an axillary lymph node dissection (ALND).

In some cases, breast reconstruction can be done at the same time as the surgery to remove the cancer. But if you will need radiation therapy after surgery, it is often better to wait to get reconstruction until after the radiation is complete.

Radiation therapy

If BCS is done, radiation therapy is usually given after surgery to lower the chance of the cancer coming back in the breast. Women who are at least 70 years old may consider BCS without radiation therapy if ALL of the following are true:

  • The tumor was 2 cm (a little less than 1 inch) or less across and it has been removed completely.
  • None of the lymph nodes removed contained cancer.
  • The cancer is ER-positive or PR-positive, and hormone therapy is given.

Radiation after BCS still lowers the chance of the cancer coming back in women who meet these criteria, but it has not been shown to help them live longer.

Some women who do not meet these criteria may be tempted to avoid radiation, but studies have shown that not getting radiation increases the chances of the cancer coming back and can shorten their lives.

If mastectomy is done, radiation therapy is less likely to be needed, but it might be given depending on the details of your specific cancer. You should discuss if you need radiation treatment with your doctor. They may send you to a doctor who specializes in radiation, called a radiation oncologist, for evaluation.

Adjuvant systemic therapy (chemo and other drugs)

For women who have a hormone receptor-positive (ER-positive or PR-positive) breast cancer, most doctors will recommend hormone therapy (tamoxifen or an aromatase inhibitor, or one followed by the other) as an adjuvant (additional) treatment, no matter how small the tumor is. Women with tumors larger than 0.5 cm (about ¼ inch) across may be more likely to benefit from it. Hormone therapy is typically given for at least 5 years.

If the tumor is larger than 1 cm (about ½ inch) across, adjuvant chemotherapy (chemo) is usually recommended. Some doctors may suggest chemo for smaller tumors as well, especially if they have any unfavorable features (such as being high-grade; hormone receptor-negative, HER2-positive; or having a high score on a gene panel such as Oncotype Dx).

For HER2-positive cancers, a year of adjuvant trastuzumab (Herceptin) is usually recommended as well.

Treating stage II breast cancer

These breast cancers are larger than stage I cancers and/or have spread to a few nearby lymph nodes.

Local therapy (surgery and radiation therapy)

Stage II cancers are treated with either breast-conserving surgery (BCS; sometimes called lumpectomy or partial mastectomy) or mastectomy. The nearby lymph nodes will also need to be checked, either with a sentinel lymph node biopsy (SLNB) or an axillary lymph node dissection (ALND).

Women who have BCS are treated with radiation therapy after surgery. Women who have a mastectomy are typically treated with radiation if the cancer is found in the lymph nodes. Some patients who have a SLNB that shows cancer in a few lymph nodes may not have the rest of their lymph nodes removed (ALND) to check for more cancer. In these patients, radiation may be discussed as a treatment option after mastectomy.

If you were initially diagnosed with stage II breast cancer and were given treatment such as chemotherapy or hormone therapy before surgery, radiation therapy might be recommended if cancer is found in the lymph nodes at the time of the mastectomy. A doctor who specializes in radiation, called a radiation oncologist, may review your case to discuss whether radiation would be helpful to you.

If chemotherapy is also needed after surgery, the radiation is delayed until the chemo is done.

In some cases, breast reconstruction can be done during the surgery to remove the cancer. But if you will need radiation after surgery, it is often better to wait to get reconstruction until after the radiation is complete.

Neoadjuvant and adjuvant systemic therapy (chemo and other drugs)

Systemic therapy is recommended for women with stage II breast cancer. Some systemic therapies are given before surgery (neoadjuvant therapy), and others are given after surgery (adjuvant therapy). Neoadjuvant treatments are often a good option for women with large tumors, because they can shrink the tumor before surgery, possibly enough to make BCS an option. But this doesn’t improve survival more than getting these treatments after surgery. In some cases, systemic therapy will be started before surgery and then continued after surgery.

The drugs used will depend on the woman’s age and the tumor’s hormone-receptor status and HER2 status. They may include:

  • Chemotherapy: Chemo can be given before or after surgery.
  • HER2 targeted drugs: If the cancer is HER2-positive, HER2 targeted drugs are started along with chemo. Both trastuzumab (Herceptin) and pertuzumab (Perjeta) may be used as a part of neoadjuvant treatment. Then trastuzumab is continued after surgery for a total of one year of treatment.
  • Hormone therapy: If the cancer is hormone receptor-positive, hormone therapy (tamoxifen, an aromatase inhibitor, or one followed by the other) is typically used. It can be started before surgery, but because it continues for at least 5 years, it needs to be given after surgery as well.

Treating stage III breast cancer

In stage III breast cancer, the tumor is large (more than 5 cm or about 2 inches across) or growing into nearby tissues (the skin over the breast or the muscle underneath), or the cancer has spread to many nearby lymph nodes.

If you have inflammatory breast cancer: Stage III cancers also include some inflammatory breast cancers that have not spread beyond nearby lymph nodes. Treatment of these cancers can be slightly different from the treatment of other stage III breast cancers. You can find more details in our section about treatment for inflammatory breast cancer.

There are two main approaches to treating stage III breast cancer:

Starting with neoadjuvant therapy

Most often, these cancers are treated with neoadjuvant chemotherapy (before surgery). For HER2-positive tumors, the targeted drug trastuzumab (Herceptin) is given as well, sometimes along with pertuzumab (Perjeta). This may shrink the tumor enough to allow a woman to have breast-conserving surgery (BCS). If the tumor doesn’t shrink enough, a mastectomy is done. Nearby lymph nodes will also need to be checked. A sentinel lymph node biopsy (SLNB) is often not an option for stage III cancers, so an axillary lymph node dissection (ALND) is usually done.

Often, radiation therapy is needed after surgery. If breast reconstruction is done, it is usually delayed until after radiation is complete. In some cases, additional (adjuvant) chemo is given after surgery as well. Women with HER2-positive cancers receive trastuzumab after surgery to complete a year of treatment with this drug. Women with hormone receptor-positive (ER-positive or PR-positive) breast cancers will also get adjuvant hormone therapy.

Starting with surgery

Another option for stage III cancers is treatment with surgery first. Because these tumors are fairly large and/or have grown into nearby tissues, this usually means getting a mastectomy. For women with fairly large breasts, BCS may be an option if the cancer hasn’t grown into nearby tissues. SLNB may be an option for some patients, but most will need an ALND. Surgery is usually followed by adjuvant chemotherapy, and/or hormone therapy, and/or trastuzumab. Radiation is recommended after surgery.

What type of drug treatment(s) might I get?

Most women with breast cancer in stages I to III will get some kind of drug therapy as part of their treatment. This may include:

The types of drugs that might work best depend on the tumor’s hormone receptor status, HER2 status, and other factors.

When is chemotherapy (chemo) used?

Chemo is usually recommended for all women with an invasive breast cancer whose tumor is hormone receptor-negative (ER-negative and PR-negative). It’s also typically recommended for women with hormone receptor-positive tumors who might benefit from getting chemo along with their hormone therapy, based on the stage and characteristics of their tumor.

Chemo, given either before surgery (neoadjuvant chemo) or after surgery (adjuvant chemo), can lower the risk of the cancer coming back, but it doesn’t remove the risk entirely. Before deciding if it’s right for you, talk to your doctor to make sure you understand the chance of your cancer returning both with or without getting chemo.

If you will be getting chemo, your doctor should discuss what specific drug regimens are best for you based on your cancer, its stage, your other health issues, and your preferences. The length of treatment usually ranges from 3 to 6 months.

When is hormone therapy used?

Hormone therapy is recommended for all women with hormone receptor-positive (ER-positive or PR-positive) invasive breast cancer, regardless of the size of the tumor or the number of lymph nodes with cancer cells. Hormone therapy is not likely to be effective for women with hormone receptor-negative tumors.

For post-menopausal women: Women who have gone through menopause and who have hormone receptor-positive tumors will generally get adjuvant hormone therapy. This might consist of:

  • An aromatase inhibitor, such as anastrozole (Arimidex), letrozole (Femara), or exemestane (Aromasin) for 5 years
  • Tamoxifen for 2 to 5 years followed by an aromatase inhibitor for 3 to 5 more years
  • Tamoxifen for 5 to 10 years (for women who can't take aromatase inhibitors)

Chemotherapy can sometimes slow or stop ovarian function for a time. Women who stopped having periods during or after chemo may need their hormone levels tested to check to see if they are truly in menopause. Many women whose periods stopped from chemo have not truly gone through menopause, and their periods will return.

For pre-menopausal women: For women who haven’t gone through menopause, the most common treatment is tamoxifen, which is taken for 5 to 10 years. Another option is an aromatase inhibitor, along with ovarian ablation. Ablation can be done with a drug called a luteinizing hormone-releasing hormone (LHRH) analog, which temporarily stops the ovaries from functioning, or with surgical removal of the ovaries (oophorectomy).

Ovarian ablation might also be considered along with tamoxifen. Still, it’s not clear that removing the ovaries or stopping them from working helps tamoxifen work better for cancers that have been removed completely, so these treatments are not standard.

If you go through menopause while being treated with tamoxifen (either naturally or because your ovaries are removed), you may be switched from tamoxifen to an aromatase inhibitor. Still, women may stop having periods on tamoxifen without truly going through menopause, so blood tests of hormone levels are often needed to see if you are in menopause and can benefit from aromatase inhibitors.

Hormone therapy and chemotherapy: Hormone therapy might be started right away if you are not getting chemo. But getting hormone therapy and chemo together can make the chemo less effective, so hormone therapy is usually not started until after chemo is completed.

When are HER2 targeted drugs used?

Women who have HER2-positive cancers are usually given trastuzumab (Herceptin) along with chemo as part of their treatment. If the treatment is given before surgery (called neoadjuvant therapy), pertuzumab (Perjeta) may be given as well. After the chemo is finished, the trastuzumab is continued to complete a year of treatment.

Because these drugs can lead to heart problems, heart function is watched closely during treatment with tests such as echocardiograms or MUGA scans.

Online tools to help make decisions

To help decide if adjuvant therapy is right for you, you might want to visit the Mayo Clinic website at and type "adjuvant therapy for breast cancer" into the search box. You will find a page that will help you to understand the possible benefits and limits of adjuvant therapy.

Other online guides, such as, are designed to be used by health care professionals. This website provides information about your risk of the cancer returning within the next 10 years and what benefits you might expect from hormone therapy and/or chemotherapy. You may want to ask your doctor if he or she uses this site.

The American Cancer Society medical and editorial content team
Our team is made up of doctors and master’s-prepared nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.

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National Comprehensive Cancer Network (NCCN). Practice Guidelines in Oncology: Breast Cancer. Version 2.2016. Accessed at on June 1, 2016.

Wolff AC, Domchek SM, Davidson NE, Sacchini V, McCormick B. Chapter 91: Cancer of the Breast. In: Niederhuber JE, Armitage JO, Doroshow JH, Kastan MB, Tepper JE, eds. Abeloff’s Clinical Oncology. 5th ed. Philadelphia, Pa: Elsevier; 2014.

Last Medical Review: June 1, 2016 Last Revised: August 18, 2016

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