Chemotherapy for Breast Cancer: What You Need to Know

If you have been diagnosed with breast cancer, you may need chemotherapy to treat it. Chemotherapy can be a long journey, depending on your circumstances. However, it may be comforting to know that chemotherapy has contributed significantly to the decreasing breast cancer mortality rates in the past few decades. Knowing what chemotherapy is and what it can do for you may also give you some strength to start or continue your chemotherapy treatment.

Chemotherapy refers to the administration of drugs with cell-killing properties. In general, it aims to eradicate cancerous tumors or reduce tumor burden, therefore reducing cancer-induced symptoms, which may result in cure or prolong life.

Chemotherapy may be used in different settings for slightly different purposes:

• Neoadjuvant therapy (sometimes also called induction therapy or preoperative therapy)

Neoadjuvant therapy is the administration of chemotherapy drugs before surgery or sometimes as the initial phase of cancer treatment. It is used to shrink a tumor too large to be operable or reduce the surgery's extensiveness. Other goals of neoadjuvant therapy include controlling tumor growth, testing tumor response to specific chemotherapy drugs, and providing symptom relief.

• Adjuvant therapy

Adjuvant therapy is the administration of chemotherapy after local treatment of the tumor, for example following surgery or radiation therapy. Its primary purpose is to eliminate cancer cells that are still present in the body. This helps prevent the formation of metastases, or cancer spread, in the future. When treating a patient's cancer, especially when it is early stage, local and targeted treatment alone may be sufficient. Outcomes of chemotherapy whether it is given neoadjuvantly or adjuvantly are equivalent. In deciding whether to proceed with adjuvant therapy, short and long-term benefits and risks are considered. In specific breast cancer types, if residual cancer cells are detected after neoadjuvant and local treatment, additional chemotherapy may be necessary in the adjuvant setting. Additionally, there are genomic tests available such as Oncotype DX, which can help doctors determine who, of women with hormone-receptor positive early-stage disease, may benefit from chemotherapy. It's important to consider all options and potential outcomes to make the best decision for each individual.

Most chemotherapy drugs act inside the cell by interacting and disrupting the cellular functions necessary for cell growth, division and survival. The major groups of chemotherapy drugs and the mechanisms they work by include:

• Alkylators and alkylator-related agents (cyclophosphamide)

These bind primarily to DNA, disrupting the normal function of DNA during cell division and gene expression.

• Platinum drugs (carboplatin)

The platinum drugs act by a similar mechanism to alkylators and alkylator-related agents.

• Antimetabolites (capecitabine, methotrexate)

Antimetabolites replace normal molecules in the synthesis of DNA and RNA or interrupt synthesis processes, thereby disrupting the normal function of DNA and RNA, which affects cancer cell growth and survival.

• Topoisomerase inhibitors (doxorubicin)

Topoisomerase inhibitors interact with the normal function of the nuclear enzymes topoisomerase I and II. These enzymes are crucial in DNA replication, transcription and repair. Interaction with these drugs leads to permanent breaks in DNA, disrupting the normal function of DNA.

• Microtubule interacting agents (paclitaxel, docetaxel)

Microtubules are cytoskeletal elements in cells necessary for many cellular functions, such as intracellular transport, motility, and cell division. Microtubule interacting agents disrupt the synthesis and break-down of microtubules, resulting in a deficiency or accumulation of excess microtubules. This then leads to loss of cell function.

• Others

Some other and newer drugs act through the induction of programmed apoptosis (programmed cell death).

Examples of chemotherapy include:

• Anthracyclines, such as doxorubicin (Adriamycin) and epirubicin (Ellence)
• Taxanes, such as paclitaxel (Taxol) and docetaxel (Taxotere)
• 5-fluorouracil (5-FU) or capecitabine (Xeloda)
• Cyclophosphamde (Cytoxan)
• Carboplatin (Paraplatin)

Chemotherapy is most commonly administered through an intravenous (IV) line, an injection or orally. In early-stage breast cancer where the intent of treatment is cure, chemotherapy drugs are often given in a combination of multiple medications to reduce the probability of tumor cell resistance, fight against different tumor cell clones and avoid excess toxicity to normal cells. The combination of drugs is normally based on tumor histology and past data from clinical trials. While in some patients, the cancer is clearly responding to treatment after the first cycle of therapy, for others response becomes obvious only after several cycles of chemotherapy.

Your chemotherapy treatment plan may differ from someone else's depending on factors such as your tumor type, what stage it is at and other health considerations. Different treatment plans may vary regarding the types of drugs to be used, the doses, and the number and periods of treatment cycles. Chemotherapy is given in cycles, with periods of rest in between to recover from the adverse effects of the prior course. Typically, a complete chemotherapy treatment will last around 3 to 6 months.

While chemotherapy has helped many patients in curing breast cancer, there is, unfortunately, a possibility of it not working, or failing to prevent cancer from growing. While rare in early-stage disease, it is possible for tumors to be unresponsive to chemotherapy drugs. In metastatic disease, is also common for chemotherapy resistance to develop while undergoing treatment. This means that tumors may respond initially but later appear resistant and lose the intended antitumor effect of the drugs.

The reasons for drug resistance may vary depending on each tumor type and each individual. The leading causes of drug resistance include:

• Drug resistance at a cellular level

Cancer cells become more resistant to chemotherapy drugs through mutations. Suppose there is drug resistance, there is no need to fret. There are ways to address it, such as switching to a new drug or combination of drugs.

• Increased drug metabolism

In some patients, their bodies may start metabolizing the chemotherapy drugs faster than necessary for the drugs to be sufficiently exposed to the tumor cells, leading to inadequate tumor cell kill.

• Lack of drug exposure to tumor

Some tumors or parts of a tumor may be poorly vascularized and thus not exposed to the drugs.

• Cell kinetic resistance

Some tumors may overcome the drug effects even if they are sensitive to them due to their fast-growing pace. These tumors tend to regrow quickly during periods of rest between chemotherapy courses.

As with all treatment methods, chemotherapy does come with a range of possible side effects. These include:

• Hair loss
• Loss of appetite
• Weight changes
• Nausea
• Diarrhea or constipation
• Lower resistance to infections
• Fatigue
• Kidney injury
• Liver injury
• Infusion reactions

Going through chemotherapy can be tough, and you might experience some temporary side effects. However, it's important to know that these are normal and usually go away after treatment. There are also medications available that can help manage these symptoms. Remember, your healthcare team is here to support you every step of the way.

Other less common but more serious side effects of chemotherapy for breast cancer are also possible.

Learn more: Side Effects of Chemotherapy for Breast Cancer

Having to go through chemotherapy can be a daunting thought. Keep in mind that your medical team is used to giving these drugs to patients and helping them get through treatment without significant side-effects and with a good quality of life. Chemotherapy is generally very effective in curing or managing breast cancer. You are not alone in this; a medical professional can answer any uncertainties or doubts.