Chemotherapy is a type of systemic therapy that is used to kill cancer cells. Chemotherapy targets cells that divide abnormally quickly; therefore, although it is a very effective way to kill cancer cells, it also kills certain healthy cells that naturally divide quickly, such as cells that make up your hair, mouth, nails, bones, and digestive tract. This means that it may have negative side effects. However, in many breast cancers, chemotherapy is worth the risk of side effects, as it effectively targets cancer cells throughout the body. Chemotherapy is usually a possibility for all stages of breast cancer except stage 0 (in situ). 

 

What is a systemic therapy?  

Systemic therapies are therapies meant to inhibit cancer growth throughout the body, rather than solely in the breast. Systemic therapies are the main treatment for stage IV breast cancers that have already spread, and are also used to prevent stage I, II, or III cancers from recurring after surgery or to prevent in situ cancers from becoming invasive.

Who usually needs chemotherapy? 
There are multiple different factors that your oncologist will consider in order to decide if you need chemo. Furthermore, chemotherapy can either be given before surgery (neoadjuvant), after surgery (adjuvant), or for metastatic breast cancer (which does not require surgery). The most common instances in which women need chemo are: 
 

• women who have had breast cancer surgery and are at a high recurrence rate, according to genomic tests (see more below) such as oncotype dx (adjuvant/after surgery chemo)

• women who have large cancers may be given chemo before surgery (neoadjuvant) in order to shrink the cancer and make the surgery less invasive. This often applies to women with multiple positive lymph nodes, abnormally large tumors, and almost always applies to those with inflammatory breast cancer. 

• those with triple negative breast cancer (TNBC) will almost always receive some form of chemotherapy (adjuvant or neoadjuvant), as neither hormone therapy nor HER2 targeted therapy will effectively target their cancer/reduce recurrence risk.

• those with metastatic cancer are usually given chemotherapy, usually coupled with a hormone therapy and/or targeted therapy, to target cancer cells that have spread to other parts of the body.

 

 

Chemotherapy and Genomic Tests

Genomic Tests are tests that look at your entire genome in order to identify genetic mutations in your cancer.  Genomic tests also provide a cancer risk or recurrence score, which can help determine how your cancer will behave, and how it will respond to certain treatments. (Genomic testing is different than genetic testing, which looks for hereditary mutations such as BCRA 1 and 2 that increase your risk of cancer). Common genomic tests include oncotype DX, mammaprint, endopredict, PAM 50, and the Breast Cancer Index. 

 

Those with a low recurrence score on a genomic test are likely to do very well with hormone or targeted therapy, and there is often not much benefit in using chemotherapy. 

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Those with a high recurrence score on a genomic test often do much better with chemotherapy (usually in addition to other systemic therapies). 

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Types of Chemotherapy

There are two main types of chemotherapy: anthracyclines (or andriamycins) such as doxorubicin and epirubican and taxanes such as paclitaxel and docetaxel. However, there are many other chemotherapy drugs such as: 

-cyclophosphamide

-methotrexate

-5-fluorouracil

-gemcitabine

-cisplatin, carboplatin

-capecitabine

-vinorelbine

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Often times, those with early stage cancers (I-III) will be given a combination of two or three chemo drugs if they are eligible for chemo.

However, stage IV metastatic patients often receive one chemo drug at a time (sometimes two). 

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Anthracyclines (Adriamycin)

Anthracyclines work by blocking an enzyme responsible for unwinding DNA. In doing this, the cancer cells can no longer divide and replicate, and will eventually die.

However, because anthracyclines can effect other healthy cells, it does have side effects. Although rare, Adriamycin is associated with cardiotoxicity (permanent heart damage). Certain conditions, doses, and drug combinations may increase your risk of cardiotoxicity: 

• Using Adriamycin for long time in large doses

• Using Adriamycin in combination with other drugs that are associated with a risk of cardiotoxicity, such as trastuzumab (a HER2 targeted therapy). Therefore, your doctor will most likely choose a different drug that does not pose the risk of cardiotoxicity to couple with Adriamycin.

• Those who have a high blood pressure, a family history of heart issues, and/or diabetes may be at higher risk. Therefore, before you start Adriamycin, you will most likely see a cardiologist who will check to make sure your heart is healthy. 

*Very rarely, Adriamycin can lead to bone marrow disease or even leukemia. However, this side effect is so rare that the benefits of Adriamycin usually outweigh this risk.  

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Taxanes 

This type of chemotherapy works by preventing cells from pulling apart from each other, and therefore preventing cancer cell division. However, because taxanes affects certain healthy cells, it also may have side effects. Although rare, taxanes are associated with the risk of peripheral neuropathy (numbness, tingling, burning, or weakness in the arms, legs, fingers and/or toes). 

Some patients are at higher risk for neuropathy: 

• those with diabetes or a history of diabetes

• those with prior neuropathy 

Therefore, if you meet one of the above criteria, you will most likely be given a different chemo drug. 

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Other Side Effects of Chemotherapy 

• fatigue is a very common effect of chemo that many women experience 

• slight decrease in cognitive function: some women may experience a decline in their memory/concentration

• appetite changes

• diarrhea, vomiting

• sores in the mouth

• higher infection risk

• easy bruising 

• menopausal symptoms

• fertility issues: this is especially an issue for premenopausal women, as loss of menstrual cycles and infertility caused by a chemo drug could lead to bone issues such as osteoporosis (there are medicines to treat this issue). Furthermore, premenopausal women should avoid getting pregnant while on chemo, as chemo can lead to birth defects; therefore sexually active women should consult their doctors about options. 

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Although there are many side effects of chemo, its ability to fight cancer throughout the body is often worth the risks. Furthermore, certain medicines, a healthy diet, and exercise may also be helpful in preventing adverse side effects. To learn more about lifestyle changes, click here.