Chemotherapy

Chemotherapy is a way doctors treat cancer using special medicines. These medicines, called chemotherapeutic agents, work by stopping cancer cells from growing or dividing. Chemotherapy can be used to try to cure cancer or to help someone feel better and live longer.

When doctors use chemotherapy, they often give many drugs together. This is because using more than one drug can be more effective against cancer. The drugs travel through the blood, so they can reach cancer cells anywhere in the body. This makes chemotherapy different from treatments like surgery or radiation, which work only in one place.

One challenge with chemotherapy is that the medicines can also affect healthy cells, especially those that grow quickly. This can cause side effects like feeling very tired, having sore mouths, or losing hair. Even though these side effects can be tough, doctors work hard to manage them and help patients through treatment.

Treatment strategies

Chemotherapy is a way doctors use special medicines to treat cancer. It can be used to try to cure cancer or to help make someone feel better and live longer.

There are different ways chemotherapy is given:

• First treatment chemotherapy is used when starting cancer treatment to try to cure the disease.
• Combined treatment chemotherapy mixes medicines with other cancer treatments like surgery or radiation.
• Follow-up chemotherapy is given after cancer treatment to help prevent the cancer from coming back.
• Using many drugs together means giving several different chemotherapy medicines at the same time. This helps stop the cancer from getting used to any one medicine.
• Chemotherapy before surgery is used to shrink a tumor before an operation.
• Chemotherapy after surgery is used to kill any remaining cancer cells after an operation.
• Ongoing low-dose chemotherapy is a regular, smaller dose of medicine to keep cancer from returning.
• Chemotherapy to reduce tumors is used when curing cancer isn’t possible, but doctors want to shrink the tumor and help the person live longer.

All chemotherapy treatments need to be carefully planned so the person can handle the treatment. Doctors give the medicine in cycles, with breaks in between, to let the body recover. How well chemotherapy works depends on the type and stage of cancer. Some cancers, like certain blood cancers, can often be cured with chemotherapy, while others, like some brain cancers, may not respond as well.

Getting the right amount of chemotherapy is important. Too little may not work, and too much can cause side effects. Doctors usually figure out the dose based on the person’s size, but many things can affect how the medicine works in the body. Some people need a different dose to get the best results with fewer side effects.

There are many types of chemotherapy medicines, each working in different ways to stop cancer cells from growing. Some stop cells from dividing, while others damage the DNA inside cells. Chemotherapy can be given in different ways, like through a vein, a pill, or even a special treatment just for one part of the body.

Adverse effects

Chemotherapeutic treatments can have many side effects, depending on the medicines used. Most medicines affect the fast-growing cells in the body, such as blood cells and the cells that line the mouth, stomach, and intestines.

One common effect is a weakened immune system. This can happen because the treatment may affect the bone marrow, where blood cells are made, leading to fewer white blood cells, red blood cells, and platelets. This can make a person feel very tired (anemia) or easy to bruise (low platelets). Some medicines can help boost white blood cells.

Another side effect is digestive trouble. Nausea, vomiting, diarrhea, stomach cramps, and constipation are common. These can sometimes be managed with special medicines. Eating enough food and staying hydrated can be challenging during this time.

Hair loss is also a well-known side effect. Hair often grows back after treatment ends, though it may look different. Some medicines are more likely to cause hair loss than others.

Other possible side effects include feeling very tired, changes in thinking or memory, and problems with nerves in the hands and feet. Some medicines can also affect the heart, liver, or kidneys, so doctors watch closely during treatment.

Some treatments might affect fertility, but there are ways to protect fertility before starting treatment. Doctors will discuss these options with patients and their families.

Limitations

Chemotherapy is not always successful, and even when it helps, it might not remove all the cancer. Many people don’t fully understand these limits. For example, in a study of people newly diagnosed with advanced cancer, most still thought chemotherapy could cure them, even though it often cannot.

The brain has a special protection system that makes it hard for some chemotherapy drugs to reach there. This system can push many drugs out of the brain, making them less effective for treating brain tumors. Only a few special drugs can pass through this protection.

Tumors also have unusual blood vessels that don’t work like normal ones. As tumors grow, parts far from blood vessels may not get enough oxygen. This causes the tumor to create new blood vessels, but these new vessels are not well formed and don’t supply blood properly. This can make it hard for drugs to reach all parts of the tumor.

Resistance

Resistance is a big reason why some cancer treatments might not work. Even though drugs are used to fight cancer, sometimes the cancer cells find ways to survive. There are two main types of this problem. The first type is called primary resistance, where cancer cells are born not responding to the drugs. The second type is called acquired resistance, where cancer cells first respond to the drugs but later find ways to avoid them.

One reason cancer cells can avoid the drugs is because of tiny pumps on their surface. These pumps can push the drugs out of the cell. While normal cells also have these pumps to stay healthy, cancer cells can make much more of them. Scientists are studying these pumps to find ways to block them so the drugs can work better. Another reason is that cancer cells can change how they work inside. For example, they can move drugs away from where they need to act, or change the targets the drugs need to affect. These changes help the cancer cells stay alive even when drugs are used.

Cytotoxics and targeted therapies

Targeted therapies are a newer kind of cancer medicine that can help avoid many problems caused by older cancer drugs. These newer drugs are split into two types: small molecules and antibodies. Older cancer drugs can harm both healthy cells and cancer cells because they do not know the difference. Targeted therapies are made to focus on special parts of cancer cells, so they can give stronger treatment to the cancer while affecting healthy cells less.

Even though these therapies usually cause fewer problems than older treatments, serious issues can still happen. At first, scientists thought these drugs would only affect one specific part of the cancer cell, but now we know they often work on several parts. One example is a treatment for a certain kind of blood cancer, using a drug that targets a special protein made by a change in the cell's genetics. Another example is a therapy used for a type of lymph node cancer, which helps the body’s immune cells fight the cancer more effectively.

Mechanism of action

Cancer happens when cells grow out of control and spread. This is because of changes in genes that control cell growth and prevent cancer. These changes happen due to things in our bodies and things in the environment.

Most chemotherapy medicines work by stopping cells from dividing. They especially target cells that divide quickly, like many cancer cells. These medicines can damage the DNA in cells or stop the parts of cells that help with division. One way they work is by triggering a process called apoptosis, which is a way for cells to die when they are damaged.

Tumors that grow quickly, such as acute myelogenous leukemia and certain lymphomas, often respond better to chemotherapy because more of their cells are dividing at any time. Slower-growing tumors may not respond as well.

The immune system can also help fight cancer when chemotherapy is used. Some chemotherapy medicines can cause tumor cells to die in a way that alerts the immune system, which then helps to fight the cancer. This can make some tumors that did not respond before become sensitive to other treatments like immune checkpoint therapy.

Other uses

Some medicines used to treat cancer can also help people with other illnesses, like certain autoimmune disorders or conditions affecting blood cells. These medicines might be used in smaller amounts to lessen side effects, or sometimes at stronger doses similar to cancer treatment.

For example, a medicine called Methotrexate is used to treat conditions like rheumatoid arthritis, psoriasis, ankylosing spondylitis, and multiple sclerosis. Another medicine, Cyclophosphamide, can help treat a kidney problem linked to systemic lupus erythematosus. Sometimes, a mix of Dexamethasone with either bortezomib or melphalan is used to treat a condition called AL amyloidosis.

These medicines are also used to prepare someone for a bone marrow transplant, which helps replace damaged bone marrow with healthy cells. This preparation is called a conditioning regimen and may involve medicines like Cyclophosphamide along with total body irradiation. The doses can be higher to remove bone marrow cells completely or lower to avoid permanent loss.

Occupational exposure and safe handling

In the 1970s, doctors found that certain cancer medicines could be dangerous. Special rules were made to help keep people safe when working with these medicines.

Healthcare workers who prepare or give these medicines can sometimes be exposed to small amounts of the drugs. This can be risky because these medicines can affect health, such as causing problems with having babies or increasing the chance of getting sick later in life. To protect workers, special safety tools like gloves, gowns, and special cabinets are used. Workers also need training to know how to handle these medicines safely.

When preparing or giving these medicines, workers must wear protective gear and follow strict steps to keep themselves and others safe. This includes washing hands, using special containers for waste, and following rules for cleaning and disposing of anything that might have touched the medicines. Regular checks and training help make sure everyone stays safe while working with these powerful drugs.

Available agents

Main article: List of antineoplastic agents

There is a long list of medicines used to treat cancer, called antineoplastic agents. Doctors use many different ways to group these medicines into various types.

History

Main article: History of cancer chemotherapy

In the early 1900s, scientists began using small chemicals to treat diseases. During World War I, a chemical called mustard gas was used in battle. They noticed it affected blood production, which gave them an idea. Maybe similar chemicals could help treat cancer.

During World War II, more research continued. In 1942, doctors tested a drug related to mustard gas on people with a type of cancer called lymphomas. The patients improved for a short time. After the war, scientists kept looking for more cancer treatments. The first real chemotherapy drug came from this work, and many more have been created since then.

Research

Main article: Experimental cancer treatments

Special treatments are being studied to make chemotherapy work better against cancer cells while causing fewer problems for healthy cells. These include using special chemicals that can find and attack cancer cells more precisely, as well as tiny particles that can carry medicine right to the tumor.

One method being tested is called electrochemotherapy, where a chemotherapy drug is given and then followed by electric pulses that help the medicine enter cancer cells more easily. Another approach is hyperthermia therapy, which uses heat to make cancer cells more open to chemotherapy. Some studies also look at adding special nutrients, like omega-3 supplements, to help patients stay stronger during treatment. These ideas are still being studied to see how well they work.

Other animals

Chemotherapy can also be used to help animals, just like it is used to help people. Doctors give medicines to animals that are sick, in much the same way they do for humans.