Why Chemotherapy?

In the early days of breast cancer treatment, doctors performed mastectomies, removing all the known cancer in the area where it began.  Too often the cancer would come back, recurring in other organs.  The cancer cells were breaking away, sometimes from what seemed to be small or early tumors, traveling through the blood and lymphatic systems to establish metastatic colonies.  The researchers realized that this problem could not be solved by doing more surgery or radiation therapy. They needed to view cancer as a systemic disease, one that potentially affected the whole body.  Doctors began using chemotherapy in addition to surgery and radiation therapy as a way of killing microscopic cancer cells for some patients with newly diagnosed breast cancers.
 

Adjuvant Chemotherapy
The use of adjuvant chemotherapy, as it is called when chemotherapy is used in addition to another form of treatment, has had a significant impact on improving survival rates for breast cancer.  Because we know that breast cancer is actually many different diseases, the goal now is to understand what makes some breast cancers aggressive and more likely to spread than others.  The complexity of your pathology report is an indication of how much progress has been made in this area.  Doctors can now look at an increasing number of biological factors related not only to the individual cancer cells but also to the tumor – both of which help predict how the cancer will behave and what treatment should be administered. While the decision about chemotherapy is based on your individual tumor and life circumstances, guidelines help make those decisions.

Generally speaking, your doctors will recommend chemotherapy if you:

• Have any positive lymph nodes, regardless of the size or type of breast cancer.
• Are premenopausal and have invasive breast cancer.  Breast cancer tends to be more aggressive in premenopausal women.
• Have what is known as triple negative breast cancer, meaning that your breast cancer is ER and PR negative and you are HER2 negative.
• Have HER2 positive breast cancer.

Neoadjuvant Chemotherapy
If a breast cancer is very large or locally advanced (involving the skin or chest wall), doctors may choose to give chemotherapy before surgery to shrink the tumor.  This is known as neoadjuvant chemotherapy.  Neoadjuvant therapy usually involves getting the same drugs before surgery that you would normally receive afterward.
 

Genomic Assays – OncotypeDX and MammaPrint
More than 50% of people diagnosed with breast cancer in the United States have estrogen receptor positive (ER+) cancer with no lymph nodes that are cancerous.  ER+ status means that the cancer can be treated effectively with hormone therapies.  The absence of any positive lymph nodes is a good prognostic sign.  As such, chemotherapy may or may not be an effective treatment.  For patients in this category, the decision about whether to have chemotherapy has traditionally been difficult.  The introduction of the OncotypeDX and similar tests have made a major contribution to improving the decision-making process for both patients and their doctors.

OncotypeDX is a genomic assay.  That means it looks at the activity of genes (21 in this case) that affect the way breast cancers grow and spread – and how they will respond to treatment.  MammaPrint is similar, but tests 70 genes.  Several other tests are currently being developed but are not yet clinically available. 

OncotypeDX tests are scored to indicate the likelihood of recurrence on a scale of 1-100.  A score of less than 18 means that the cancer is very unlikely to recur and chemotherapy provides little if any benefit.  A score of 18-31 indicates an intermediate risk of recurrence.  This is an area in which chemotherapy may or may not be beneficial, and requires a discussion between doctor and patient to determine the best course of treatment.  A score of more than 31 indicates a high risk of recurrence and a strong potential benefit for chemotherapy that outweighs the risk of side effects.

If you think you are a candidate for this test, talk to your doctor.  The test should be performed only at a lab that is qualified and experienced in doing genomic assays.

Next: Side Effects of Chemotherapy.