Chemotherapy: How It Works, Treatment Cycles, Side Effects and What to Expect

What Is Chemotherapy?

Chemotherapy, often called chemo, is a cancer treatment that uses medicines to destroy cancer cells or stop them from growing and dividing.

Because cancer cells often divide rapidly, chemotherapy can be effective against many types of cancer.

However, some healthy cells also divide quickly. These include cells in the hair follicles, digestive system and bone marrow. When chemotherapy affects these healthy cells, side effects can occur.

Not every cancer patient needs chemotherapy, and there is no single chemotherapy treatment that works for every type of cancer.

Why Is Chemotherapy Used?

Chemotherapy may be used for several different purposes.

It can be given to:

• Cure certain cancers
• Destroy cancer cells that may remain after surgery
• Reduce the size of a tumor before surgery or radiotherapy
• Slow the growth or spread of cancer
• Treat cancer that has spread to other parts of the body
• Relieve symptoms caused by advanced cancer

Chemotherapy may be the main treatment, or it may be combined with surgery, radiotherapy, immunotherapy, targeted therapy or other treatments.

How Is Chemotherapy Given?

Chemotherapy can be delivered in several ways.

The most common is intravenous chemotherapy, where medicine is given directly into a vein.

Other methods may include:

• Tablets or capsules taken by mouth
• Injections under the skin or into a muscle
• Medication delivered directly into a body cavity
• Treatment delivered into the fluid surrounding the brain and spinal cord
• Medication delivered directly into an artery supplying the tumor
• Creams applied to the skin for certain cancers

The method used depends on the type of cancer and the chemotherapy drug being given.

What Is a Chemotherapy Cycle?

Chemotherapy is often given in cycles.

A cycle consists of a treatment period followed by a rest period.

For example, a patient may receive chemotherapy on one day and then have several weeks without treatment before the next cycle.

The rest period allows healthy cells and the body to recover before another dose is given.

The number and length of cycles vary depending on:

• Type of cancer
• Stage of the disease
• Chemotherapy drugs being used
• Treatment goal
• How the cancer responds
• How well the patient tolerates treatment

Doctors may sometimes delay treatment or adjust the dose if blood counts are too low or side effects become significant.

What Happens Before Chemotherapy?

Before treatment begins, doctors assess the patient's general health and determine whether chemotherapy can be given safely.

This may include:

• Blood tests
• Kidney and liver function tests
• Heart assessment for certain drugs
• Imaging examinations
• Review of current medications
• Evaluation of infections or other medical conditions

Some patients may also have a port or other venous access device placed to make repeated intravenous treatment easier.

What Happens During a Chemotherapy Session?

The experience depends on the drug and how it is given.

Intravenous chemotherapy may take anywhere from a short period to several hours.

During treatment, nurses monitor the patient and may give additional medicines to reduce nausea, allergic reactions or other side effects.

Some chemotherapy treatments can be given in an outpatient clinic, meaning the patient can return home the same day.

Other treatments may require hospitalization, particularly when intensive chemotherapy is needed.

What Are the Most Common Side Effects?

Side effects vary considerably between patients.

They depend on the specific medicines, dosage, treatment duration and the patient's general health.

Possible side effects include:

• Fatigue
• Nausea and vomiting
• Loss of appetite
• Mouth sores
• Diarrhea or constipation
• Hair loss
• Lower blood cell counts
• Increased risk of infection
• Easy bruising or bleeding
• Anemia
• Numbness or tingling in the hands and feet
• Skin or nail changes
• Changes in taste
• Fertility problems

A patient does not necessarily experience all of these effects.

Modern supportive treatments can prevent or reduce many chemotherapy-related symptoms, including nausea and vomiting.

Does Everyone Lose Their Hair?

No.

Hair loss depends on the chemotherapy drugs being used.

Some treatments cause significant hair loss, while others cause thinning or no noticeable hair loss.

If hair loss occurs, it is usually temporary. Hair commonly begins to grow back after chemotherapy is completed, although its color or texture may initially be different.

Why Can Chemotherapy Increase the Risk of Infection?

Some chemotherapy medicines reduce the number of white blood cells produced by the bone marrow.

When certain infection-fighting white blood cells become very low, the body may have more difficulty fighting bacteria, viruses and other infections.

Doctors monitor blood counts throughout treatment.

Patients should follow their oncology team's instructions about fever and infection carefully, because infections during periods of low immunity can sometimes become serious quickly.

Can Chemotherapy Cause Nausea?

Yes, but nausea and vomiting can often be controlled.

Doctors commonly give anti-nausea medicines before chemotherapy and may prescribe additional medication for use at home.

The risk of nausea depends on the chemotherapy drug and dose.

Patients should tell their treatment team if nausea is not controlled, because the medication plan can often be adjusted.

How Do Doctors Know Whether Chemotherapy Is Working?

Doctors monitor the response to treatment throughout the chemotherapy program.

Depending on the cancer, this may include:

• Physical examination
• Blood tests
• Tumor-marker tests
• CT scans
• MRI scans
• PET scans
• Bone marrow examinations

The results help the oncology team decide whether to continue the same treatment, adjust the dose or consider a different approach.

Can Chemotherapy Be Combined With Other Treatments?

Yes.

Many patients receive chemotherapy as part of a broader cancer treatment plan.

For example, chemotherapy may be given before surgery to shrink a tumor or after surgery to reduce the chance that remaining cancer cells will cause the disease to return.

It may also be given at the same time as radiotherapy in certain cancers.

The combination chosen depends on the cancer type, stage and individual patient.

Life During Chemotherapy

Many patients continue some normal daily activities during chemotherapy, while others need more rest or changes to their routine.

How a patient feels can vary throughout each treatment cycle.

Good communication with the oncology team is important. Patients should report side effects rather than assuming they must simply tolerate them.

Nutrition, hydration, infection prevention, rest and appropriate physical activity can all form part of supportive care.

Chemotherapy is not one single treatment. It includes many different medicines and treatment combinations, and each patient's experience can be different.

A personalized treatment plan from an oncology team helps balance the potential benefits of chemotherapy with its possible side effects and the patient's overall health.