Breast cancer chemotherapy: FAQ

What is chemotherapy?

Chemotherapy is the use of any drug or medication to treat disease. For example, antibiotics are a type of chemotherapy. Today, however, the word chemotherapy has come to refer to medications used for treating cancer.

Chemotherapy travels in the bloodstream and can reach cancer cells in distant organs that may have not been removed by surgery or may not be the target of radiation treatment.

Chemotherapy is used in 3 ways to treat breast cancer:

1. As adjuvant therapy to prevent recurrence.
2. As the main or primary treatment for advanced cancers.
3. To relieve the symptoms from cancers that have spread.

Why have chemotherapy after you've just had surgery to remove the tumour?

Cancers are made up of billions of cells that can travel from one part of the body to the other. Cancers that develop away from the original tumour are known as metastases. When only a few cancer cells have traveled away from the original tumour, doctors may be unable to detect them even with sophisticated scans and blood tests. These tiny metastatic deposits can grow and ultimately cause incurable disease.

Because we cannot detect these tiny metastases we need to learn from the experience of other women over years of research, which patients may be at a high risk of recurrent disease at some time in the future and which patients may be cured with surgery alone.

The goal of chemotherapy is to reduce the number of recurrences and to increase the number of women who are cured after a diagnosis of breast cancer. Research has shown that both premenopausal and postmenopausal women benefit from chemotherapy, and that chemotherapy given at the time of diagnosis can significantly reduce the risk of the cancer recurring.

How effective is chemotherapy in reducing the risk of recurrence?

Studies suggest that chemotherapy can decrease the risk of recurrence by about 25% to 33%. This means that:

• If the risk of recurrence is 90%, chemotherapy will decrease it to 60% to 68% and improve the chance of cure from 28% to 32% to 40%.
• If the risk of recurrence is 60%, chemotherapy will decrease it to 40% to 45% and improve the chance of cure from 40% to 55% to 60%.
• If the risk of recurrence is 10%, chemotherapy will decrease it to 6% to 7.5% and improve the cure rate from 90% to 93%.

Is chemotherapy right for you?

The recommendations for chemotherapy depend on your risk category as determined by your pathology report and on the evidence that chemotherapy works. This evidence is constantly changing as new studies are reported, as new drug combinations are tested and as we learn more about how breast cancer behaves. We know that chemotherapy does not guarantee a cure, because many women relapse after treatment. Better chemotherapy is needed, and research is ongoing, and there are a number of new chemotherapy combinations. You should discuss with your doctor why you may need chemotherapy and which chemotherapy is best for you.

What is a risk/benefit assessment?

A risk/benefit assessment helps your doctor to evaluate the:

• risk of recurrence (what is the chance the cancer will come back?)
• benefit of chemotherapy (how much will the chemotherapy help and by how much will it decrease the risk or recurrence?)
• side effects of chemotherapy (how much toxicity is it going to cause short- and long-term side effects?)

In other words, your doctor needs to determine if the potential benefits outweigh the side effects in your situation.

What are the indicators of an increased risk of breast cancer recurrence?

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What other factors are important in the decision-making process?

• Your age - younger women have more benefit from chemotherapy than elderly women and may tolerate it better.
• Your general health - women with poor health and other diseases may have more toxicity and less benefit.
• Estrogen receptors - if they are high and the risk of recurrence is low, antiestrogen therapy may be prescribed without chemotherapy.
• Extreme risk - in cases where there is a very big tumour or a lot of lymph nodes with cancer involvement, we describe an "extreme" risk category. Currently, there is no evidence that these tumours should be treated with different chemotherapy but studies are being done to try to improve the chances of survival in this situation.