Cancer in children is rare, but some types are more common than others. When cancer occurs in children, it often affects:

• Blood cells
• Lymph system
• Brain
• Liver
• Bones

The most common cancer in children affects blood cells. It is called acute lymphoblastic leukemia.

While these cancers can happen in adults, they are less common. Other types of cancer, such as prostate, breast, colon, and lung are much less likely in children than adults.

Most of the time the cause of a childhood cancer is not known.

Some cancers are linked to changes in certain genes (mutations) passed from parent to child. In some children, gene changes that occur during early growth in the womb increase the risk of leukemia. However, not all children with the mutation get cancer. Children born with Down syndrome are also more likely to develop leukemia.

Unlike adult cancers, childhood cancers do not occur due to lifestyle choices, like diet and smoking.

It is hard to study childhood cancer because it is rare. Scientists have looked at other risk factors including chemicals, toxins, and factors from the mother and father. The results of these studies show few clear links to childhood cancers.

Since childhood cancers are so rare, they are often difficult to diagnose. It is not uncommon for symptoms to be present for days or weeks before a diagnosis is confirmed.

Treatment for childhood cancer is similar to treatment for adult cancer. It may include:

• Chemotherapy
• Radiation therapy
• Medicines
• Immune therapy
• Stem cell transplants
• Surgery

For children, the amount of therapy, type of medicine, or need for surgery may differ from adults.

In many cases, the cancer cells in children respond better to treatments compared to adults. Children can often handle higher doses of chemo drugs in shorter periods before side effects occur. Children seem to bounce back sooner from treatments compared to adults.

Some treatments or medicines given to adults are not safe for children. Your health care team will help you to understand what is right for your child depending on their age.

Children with cancer are best treated in children's cancer centers attached to major children's hospitals or universities.

Treatment for cancer may cause side effects.

Mild side effects, such as nausea, vomiting, rash, pain, and upset stomach can be bothersome for children. Other common effects include:

• Infections
• Mouth sores
• Need for transfusions
• Poor appetite (needing nutritional support)
• Hair loss
• Diarrhea or constipation
• Hearing damage

Rarely the treatment can cause serious damage to the body that can be permanent or very serious and life threatening. The medicines used to help reduce these symptoms may be different for children compared to adults.

Other side effects can harm their growing bodies. Organs and tissue may be changed by treatments and affect how they function. Cancer treatments may also delay growth in children, or cause another cancer to form later on. Sometimes these harms are noticed weeks or several years after treatment. These are called "late effects."

Your child will be watched closely by your health care team for many years to look for any late side effects. Many of them can be managed or treated.

American Cancer Society website. What are the differences between cancers in adults and children? www.cancer.org/cancer/cancer-in-children/differences-adults-children.html. Updated October 14, 2019. Accessed November 8, 2022.

National Cancer Institute website. Cancer in children and adolescents. www.cancer.gov/types/childhood-cancers/child-adolescent-cancers-fact-sheet. Updated November 4, 2021. Accessed November 8, 2022.

National Cancer Institute website. Children with cancer: A guide for parents. www.cancer.gov/publications/patient-education/guide-for-parents. Updated September 2015. Accessed November 8, 2022.

Updated by: Stergios Zacharoulis, MD, Associate Professor of Pediatric Oncology at Columbia University Irving Medical Center, New York, NY. Review provided by VeriMed Healthcare Network. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.