Since cancer cells are characterized by their rapid growth, chemotherapy is designed to specifically target rapidly dividing cells. There are many different chemotherapy drugs [MB1] and their mechanisms for killing cancer cells vary, from damaging the genetic material of the cells to interfering with the growth and division of the cells.1 Not everyone with breast cancer will need chemotherapy. Gene expression testing [MBA2] can be a useful test to determine which women will benefit from chemotherapy by assessing the likelihood of cancer recurrence.2

Chemotherapy can be performed after surgery (adjuvant chemotherapy) or before surgery (neoadjuvant chemotherapy). [MB3] Adjuvant chemotherapy is used to kill microscopic cancer cells throughout the body that cannot be seen by imaging. These cells can break off from the primary tumor and form tumors in other places in the body. Neoadjuvant chemotherapy can be used to shrink the size of a tumor if it is large. Receiving chemotherapy before surgery can allow operation on tumors that were previously too large to remove. Additionally, shrinking the tumor can allow a less extensive surgery to be performed. Neoadjuvant chemotherapy also allows doctors to assess how the cancer responds to chemotherapy. For advanced breast cancer—cancer that has spread beyond the breast and lymph nodes—chemotherapy is the primary treatment.2 Surgery is not typically done for advanced cancer unless the tumor is causing problems such as pain or impeding the function of an organ.3

Chemotherapy for breast cancer is given intravenously or orally. There are many other ways chemotherapy may be administered [MB4] for other types of cancer.2 When receiving chemotherapy intravenously, the drug may be injected with a syringe over a period of 10-15 minutes or infused over a longer period of 30 minutes to a few hours. A continuous infusion is another option that utilizes an electronic IV pump to deliver the drug over a period of 1 to 7 days.4 A larger and sturdier needle placed into a large vein near the heart, known as a central venous catheter (CVC[MB5] ), is often needed to deliver chemotherapy.2 The most common types of CVCs are an implanted port and a peripheral inserted central catheter (PICC line).5

Chemotherapy is administered in cycles, with a rest period to allow time for recovery. Cycles are usually 2 or 3 weeks long, with the schedule changing based on the medication. The medication may be given only once at the beginning of each cycle, for a few days in a row, or once a week. Adjuvant and neoadjuvant chemotherapy typically last 3-6 months, while the length of treatment for advanced cancer varies based on how the cancer responds and what side effects the patient has. Dose-dense chemotherapy is a method that gives cycles of chemotherapy medications closer together. For example, a drug that is typically given in 3-week cycles may be given in 2-week cycles using the dose-dense chemotherapy method. This form of chemotherapy has been shown to lower risk of cancer recurrence but can have greater side effects, such as substantially lowering white blood cell count.2 White blood cells are a major part of the immune system; therefore, having low white blood cell levels increases the risk of developing an infection.6

References

1.     Common Types of Chemotherapy for Breast Cancer https://www.healthline.com/health/common-types-chemotherapy-breast-cancer (accessed May 27, 2021).

2.     Chemotherapy for Breast Cancer https://www.cancer.org/cancer/breast-cancer/treatment/chemotherapy-for-breast-cancer.html (accessed May 26, 2021).

3.     Breast Cancer Surgery https://www.cancer.org/cancer/breast-cancer/treatment/surgery-for-breast-cancer.html (accessed May 21, 2021).

4.     Intravenous Chemotherapy https://www.drugs.com/cg/intravenous-chemotherapy.html (accessed Jun 2, 2021).

5.     Tubes, Lines, Ports, and Catheters Used in Cancer Treatment https://www.cancer.org/treatment/treatments-and-side-effects/planning-managing/tubes-lines-ports-catheters.html (accessed May 27, 2021).

6.     What is Blood Made Up Of - What is Human Blood Made Up Of https://www.instah.com/health-questions/what-is-human-blood-made-up-of/ (accessed May 13, 2021).

 [MB1]Link to ‘chemotherapy drugs’ article

 [MBA2]Link gene expression testing article

 [MB3]Link to ‘chemotherapy terms’ article

 [MB4]Link to ‘how chemotherapy is administered’ article

 [MB5]Link to ‘central venous catheters’ article