Breast Cancer Chemotherapy Side Effects

Like nearly all breast cancer treatments, chemotherapy can cause side effects. The side effects you have will vary based on the chemotherapy medicines prescribed, the number of times you’ll receive these medicines, and your general health. Because everyone is different, you may experience different side effects — or more or less severe side effects — than someone else on the same chemo regimen.

Before you begin chemotherapy, ask your doctor to explain the benefits of the medicine(s) recommended for you. Your healthcare team should also explain the possible side effects of each medicine you’ll receive and plans for how they will help you manage these side effects. If they don’t tell you how to reach them for questions or concerns about side effects, be sure to ask.

Chemotherapy is an effective breast cancer treatment because it kills cells that grow and divide quickly, like cancer cells. As chemotherapy travels throughout the body, though, it doesn’t just knock out cancer cells; it kills fast-growing healthy cells, too. Some of the body’s fast-growing cells live in hair follicles, bone marrow, the mouth and intestines, and fingernails and toenails.

Read more of our special series to learn about ways to reduce chemo side effects, how to know if you need chemo, and why chemo doses are sometimes too high — and what you can do about it.

Hair loss, nausea and diarrhea, mouth sores, and more occur when chemo kills the healthy cells along with the cancer cells. Some chemotherapy medicines also may damage cells in your heart, kidneys, lung, or nervous system. 

Short-term side effects start at or near the beginning of chemotherapy treatment, but usually go away when chemo ends.

Chemotherapy affects the cells in your mouth and digestive tract because they, like cancer cells, divide quickly. This can lead to appetite changes, mouth and throat sores, constipation, diarrhea, nausea, taste and smell changes, vomiting, and weight changes.

Chemotherapy can cause hair loss; nail changes, such as thickening or thinning or nails that fall off completely; rash; sensitive skin; or neuropathy (nerve damage in the hands and feet).

Being diagnosed with breast cancer is stressful, as is treatment and worrying about side effects. While chemo brain or brain fog happens to a lot of people during chemotherapy, it can be a side effect of nearly all breast cancer treatments. Mood swings, anxiety, and fatigue are also common.

Some chemotherapy medicines affect the ovaries and may stop periods and ovulation — a condition known as early menopause or chemotherapy-induced menopause. Symptoms may include hot flashes, loss of libido, and vaginal changes, such as vaginal dryness and vaginal thinning.

Chemotherapy is the cancer treatment most likely to weaken the immune system. That’s because the cells in your bone marrow also rapidly divide. Your bone marrow makes red blood cells, white blood cells, and platelets. So as chemotherapy damages the bone marrow, it’s less able to produce those types of blood cells. This can lead to anemia (low red blood cell counts), low white blood cell counts, a higher risk of infection, and bleeding and bruising problems. In most cases, these lowered blood counts almost always return to normal when chemotherapy ends. 

If you stopped having periods during chemotherapy, your periods may resume months after your chemotherapy stops. However, depending on your age and the type of chemo you received, chemotherapy-induced menopause may be permanent. 

Chemotherapy medicines also affect sperm cells. If all the immature cells that divide to make new sperm — the spermatogonial stem cells — are damaged and can’t produce mature sperm cells, it can cause permanent infertility.

Chemotherapy medicines can increase your risk of osteopenia and osteoporosis, two conditions in which your bone density and bone strength is lower than normal. If left untreated, these conditions dramatically increase your risk of breaking a bone. Bone loss is more likely to happen if chemotherapy makes your periods stop permanently.

Anthracycline chemotherapy medicines — which include Adriamycin (chemical name: doxorubicin), Doxil (chemical name: doxorubicin), and Ellence (chemical name: epirubicin) — can have toxic effects on the heart. Doctors are likely to recommend ongoing heart monitoring for people who have received an anthracycline or other chemotherapy medicines that can cause heart problems. 

Some chemotherapy medicines can cause lung problems, including shortness of breath or a persistent cough. Because chemotherapy affects the immune system, you may have a higher risk of lung inflammation and infection, which can ultimately result in bronchitis or pneumonia.

In rare cases, chemotherapy for breast cancer can lead to a secondary cancer, such as leukemia (cancer of the blood cells) years after chemotherapy is completed.

Because these long-term side effects may take years to develop, it’s important to get follow-up care after breast cancer treatment is completed. Follow-up care helps ensure you are regularly screened for these and other chemotherapy side effects. Consider working with your healthcare team to create a survivorship care plan that includes a summary of all the treatments you’ve received, any side effects you might have, and recommendations for follow-up appointments. 

Chemotherapy side effects can start during your first treatment or after treatment. 

Some chemotherapy medicines may cause side effects that don’t show up until many years after treatment is completed. For example, women who receive certain chemotherapy medicines have a higher-than-average risk of developing a second cancer, such as leukemia, later in life. If they do develop a second cancer, this would be a late side effect of treatment for the first cancer.

Many side effects go away fairly quickly — in a week or two — after the entire course of treatment is completed. But some side effects, like fatigue or neuropathy, may take months to resolve. Other side effects can last for many years or a lifetime after treatment if the medicines damage the nerves, heart, or reproductive tract – one of many reasons that a good follow-up care plan is so important.

For many people, the worst day for side effects, such as fatigue, nausea, and vomiting, is the day after you receive the treatment. By about three or four days after treatment, many people begin to feel a bit better.

The possible side effects of oral chemotherapy are nearly the same as chemotherapy given through an IV. The main difference is that people who receive an infusion may have a reaction at the site where the port or IV is placed. 

There are many ways to help ease side effects from chemo. Medicines as well as complementary therapies, such as acupuncture, can help reduce some side effects, like hot flashes. Exercise also has been shown to help with several side effects, including fatigue, pain, and neuropathy.

It’s important to tell your healthcare team about any and all side effects you’re having, even if you think they’re minor. Some side effects that seem mild may be the beginning of more serious issues.

Before you start chemo, your treatment team should give you a phone number you can call if you feel unwell at any time during your treatment.

Between each chemotherapy cycle, your healthcare team will examine you to see how you’re feeling and ask about side effects.

You may want to keep a side effects diary to record the date and time any side effects occur, as well as how long they last and how severe they are. This helps your doctor and you make informed decisions about how to treat the side effects or possibly adjust your chemotherapy regimen.

Although studies usually identify the side effects that a medicine may cause, some people may have reactions that weren't seen in any study. If this happens, your doctor may notify the FDA.