Chemotherapy Definition

Cancer is a pretty scary word. So is the word chemotherapy. It is natural for you to have feelings of fear, despair, and helplessness. You are facing an illness that could be life-threatening. You are about to receive a treatment that we hear so much negative about. You are facing the unknown and that is always scary.

What you should know is that chemotherapy has been extensively researched. Cancers of all types have also been carefully examined to help researchers determine the most effective treatment types to fight the cancer cells. Because different types of cancers react differently to different types of research, you should know that your doctor will only recommend chemotherapy if it is absolutely needed. And, while there are no guarantees with cancer, following your doctor’s orders and receiving chemotherapy can increase your chances at survival.

What is Chemotherapy?

Chemotherapy, quite simply, is the use of drugs to treat a disease or condition. The most common condition that chemotherapy is used to treat is cancer. However, there are other conditions that are autoimmune in nature, like lupus. It has also been used to treat arthritis.

How Chemotherapy Works

Cancer happens when cells within the body divide, forming more cells at a rate that is abnormal. The cells are unable to stop dividing and eventually create a tumor. Chemotherapy works by stopping the division of the cells. If the cells are unable to divide, they die. While chemotherapy attempts to cause the least amount of damage possible, healthy cells are somewhat damaged during chemotherapy but, because they are healthy, they are able to recover from the treatment. Cancer cells, as long as the treatment is effective, are unable to reproduce.

Generally, cell division happens in cycles. This is why chemotherapy is often given in rounds. By treating the body at different intervals, the chemotherapy has the best chance at fighting the cancerous cells and putting your cancer into remission. It is important to realize that cancer can and sometimes does return. Your doctor should talk to you about your prognosis and what your chances are of beating the cancer for good.

Types of Chemotherapy

Not all chemotherapy drugs are the same. There are many different drugs used, each coming from a different source. There are six different groups of chemotherapy, each being used for a different type of cancer. You should also understand the difference between cell-specific and non-cell-specific drugs. Cell-specific chemotherapy drugs kill cancer cells while they are actually dividing. Non-specific chemotherapy drugs kill cancer cells while they are at rest. The type of chemotherapy used will depend on how the type of tumor you have divides and spreads.

Topoisomerase inhibitors are used to stop DNA replication that occurs in certain types of cancers. There are two different types of Topoisomerase inhibitors: Topoisomerase I inhibitors include the drugs ironotecan and topotecan. Topoisomerase II inhibitors include the drugs amasacrine, etoposide, etoposide phosphate, and teniposide.

Antitumor antibiotics are chemotherapy drugs that come from certain species of fungus. These drugs are used to act during many different phases of cell cycle and target only the cancer cells. There are three different types of antitumor antibiotics: anathracyclines, which include doxorubicin, daunorubicin, epirubicin, mitoxantrone, and idarubicin; chromomycins, which include dactinomycin and plicamycin; and miscellaneous antitumor antibiotics which include mitomycin and bleomycin. 

Antimetabolites are considered cell-specific and attack during specific cell-cycle phases. These chemotherapy drugs contain substances that are very similar to substances already contained within the cells and they are classified according to the substance that they contain. There are four different types. Folic acid antagonists include only the drug methotrexate. Pyrimidine antagonists include the drugs 5-fluorouracil, foxuridine, cytarabine, capecitabine, and gemcitabine. Purine antagonists include 6-mercaptopurine and 6-thioguanine. Adenosine deaminase inhibitors include cladribine, fludarabine, nelarabine, and pentostatin.

Alkylating agents do most of their work during the cells’ resting phase. They are not cell-specific. Alkylating agents are grouped by the materials they contain. Mustard gas derivatives include mechlorethamine, cyclophosphamide, chlorambucil, melphalan, and ifosfamide. Ethylenimines include thiotepa and hexamethylmelamine. Alkylsufonates only include the drug busulfan. Hydrazines and triazines include the drugs altretamine, procarbazine, dacarbazine, and temozolomide. Nitrosureas include the drugs carmustine, lomustine, and streptozocin. Metal salts include carboplatin, cisplatin, and oxaliplatin.

Plant alkaloids are derived from specific types of plants. These are cell-specific chemotherapy drugs. There are four different types of plant alkaloid chemotherapy drugs. Vinca alkaloids, which are derived from the periwinkle plant, include the drugs vincristine, vinblastine, and vinorebline. Taxanes, which are derived from the bark of the Pacific Yew tree, includes the drugs paclitaxel and docetaxel. Podophyllotoxins, which are derived from the May apple plant, includes the drugs etoposide and tenisopide. Camptothecan analogs, which are derived from the camptotheca acuminate, otherwise known as the Asian “Happy Tree,” includes the drugs Irinotecan and topotecan.

Why are There Different Types of Chemotherapy?

As mentioned, different types of cancer react differently to different types of cancer treatment. This is why there are many different types of chemotherapy. The different types of chemotherapy contain different types of drugs that fight against specific types of cancers. Some cancers do not respond to chemotherapy. Others are chemo sensitive and respond only to chemotherapy. Others only respond to certain types of chemotherapy drugs. Your doctor will consider the type and severity of your cancer to determine which type of treatment and chemotherapy is best for you.