Cancer in children occurs when abnormal cells grow and divide uncontrollably, disrupting the body’s natural processes. Unlike normal cells that grow and die in an orderly way, cancer cells multiply quickly and fail to die when they should. This can lead to the formation of tumors or interfere with the body’s ability to function properly.

The two most common treatments for childhood cancer are chemotherapy and radiation therapy. While both are designed to kill fast-growing cancer cells, they may also affect healthy cells that grow rapidly, such as those in the blood, digestive system, and hair follicles. As a result, side effects are common, and they vary from child to child depending on the type of cancer, the treatment plan, and the child’s overall health.

Chemotherapy vs. Radiation Therapy

Although chemotherapy and radiation therapy are both used to treat cancer, they differ in how they work and where they target cancer cells.

• Chemotherapy uses medications that travel through the bloodstream to target fast-dividing cells anywhere in the body. It is systemic, meaning it can affect areas beyond the original tumor site. While effective in stopping the spread of cancer, chemotherapy often impacts other fast-growing healthy cells, leading to various side effects.

• Radiation therapy focuses specifically on the area where cancer cells are present. It works by damaging the DNA of cancer cells, causing them to die. While it can also affect nearby healthy cells, those cells usually recover after treatment ends. The side effects of radiation tend to be localized to the treated area.

Some children may undergo only one form of treatment, while others may need a combination of both, or even additional therapies.

Common Side Effects of Chemotherapy and Radiation

Side effects vary widely. Some appear during treatment and fade over time, while others may persist or develop later in life. Below are the most commonly observed side effects, along with explanations and management strategies.

Fatigue

One of the most common effects, fatigue can occur during treatment and last for a short period afterward. It may be intensified by anemia or low red blood cell levels. Children should be encouraged to rest and avoid physically demanding activities during recovery.

Flu-Like Symptoms

Some medications cause temporary symptoms that resemble a cold or flu, such as chills, coughing, and nasal congestion. Staying well-hydrated and notifying the healthcare team of any fever is important.

Nausea and Vomiting

These are common, particularly with chemotherapy or when radiation targets the abdominal area. Small, frequent meals and hydration with broths or juices can help. Doctors may also prescribe anti-nausea medication if necessary.

Weight Changes

Children may lose or gain weight depending on how treatment affects their appetite and digestion. Steroid medications can lead to increased appetite and weight gain, while chemotherapy might reduce interest in food. Consult your healthcare provider for personalized nutritional support.

Hair Loss

Hair thinning or complete loss can occur with chemotherapy and with radiation directed at the head. The emotional impact of hair loss can be significant for children. Families are encouraged to explore options such as hats, scarves, or wigs and to focus on comfort and self-confidence during this time.

Anemia

Damage to red blood cells can cause fatigue, paleness, or rapid heartbeat. Blood tests will be used to monitor levels, and in some cases, transfusions may be needed.

Increased Bleeding Risk

Low platelet counts (thrombocytopenia) can lead to bruising, nosebleeds, or gum bleeding. Children should avoid rough play, and caregivers should use soft toothbrushes and be cautious with dental hygiene. Platelet transfusions may be needed in some cases.

Higher Risk of Infection

Treatment can reduce white blood cells, particularly neutrophils, increasing infection risk (neutropenia). Children should avoid crowded places and anyone who is sick. Signs of infection—such as fever, chills, or painful urination—should be reported immediately. Good hygiene, including frequent handwashing, is essential.

Pain

Headaches, muscle aches, stomach pain, and nerve-related discomfort (such as tingling in the hands or feet) can occur. Some cases may require prescription pain relief. Always consult your healthcare provider before giving any over-the-counter medication.

Mouth and Throat Sores

Irritation of the mouth, gums, and throat may occur, especially with radiation to the head and neck. Avoiding acidic foods and using prescribed rinses can help relieve symptoms. Oral hygiene remains critical to avoid infections.

Hearing Changes

Certain medications may affect the ability to hear high-pitched sounds. Regular hearing screenings may be conducted during treatment to monitor for changes.

Constipation

Some chemotherapy drugs and pain medications can slow digestion. Encouraging fluid intake, movement, and dietary fiber can help. Medical treatment may be needed if constipation persists.

Diarrhea

Diarrhea can result from medications or antibiotic use. Ensure your child stays hydrated. Notify the care team if diarrhea becomes severe or if your child can’t tolerate fluids.

Skin Reactions

Skin may become dry, red, or irritated. Radiation can cause localized blistering or peeling. Loose, breathable clothing and doctor-recommended ointments can relieve discomfort. Sun protection is especially important in treated areas.

Heart Effects

Though rare, some medications may cause heart damage. Doses are carefully managed, and heart function is monitored with echocardiograms during treatment.

Lung Problems

Some treatments can cause lung inflammation or scarring. Breathing tests and x-rays are often used to track lung health during therapy.

Kidney and Bladder Effects

Chemotherapy may affect kidney and bladder function. Blood and urine tests help monitor for problems. Increased fluid intake is encouraged, and any blood in the urine should be reported.

Blood Clots

Some medications may increase the risk of clotting, which can be dangerous. Children should stay hydrated and move around when possible. Signs like swelling or unusual pain in the limbs should be reported immediately.

How Long Do Side Effects Last?

The duration of side effects depends on the type and intensity of treatment, as well as the child’s general health. While many symptoms fade after treatment, some may persist or appear later in life. These long-term effects can include issues with growth, cognition, organ function, or fertility. Healthcare teams will review these risks with families and take steps to reduce long-term complications where possible.

Helping Children Understand Treatment

Cancer treatment can be emotionally challenging. Children may feel scared, angry, or confused. Supporting their emotional well-being is just as important as managing physical symptoms. Here's how parents and caregivers can help:

• Explain treatment in simple, age-appropriate terms

• Encourage open questions and answer honestly

• Involve professionals like child psychologists, social workers, or child life specialists

• Offer comfort through routines, distractions, and reassurance

Hospitals often provide support groups, educational tools, and counseling to help children and families navigate this journey together.