APRIL: CANCER IN CHILDREN AWARENESS MONTH!

Written by Alex Asuncion

What are the differences between cancers in adults and children?

The types of cancers that develop in children are different from the types that develop in adults. Although there are exceptions, childhood cancers tend to respond better to chemotherapy. Children also tolerate chemotherapy better than adults. But, because chemotherapy can have some long-term side effects, children who survive their cancer need careful attention for the rest of their lives.

What is childhood cancer?

Because of significant advances in treatment, 80% of children with cancer will survive 5 years or more. This is a major increase from before the 1970s, when the 5-year survival rate was less than 50%.

Despite its rarity and the major advances in treatment and supportive care, cancer is still the leading cause of death from disease in children younger than 15 years old. Cancer deaths are second only to accidents in most age groups.

The types of cancers that occur in children vary greatly from those seen in adults. Leukemias, brain and other nervous system tumors, lymphomas (lymph tissue cancers), bone cancers, soft tissue sarcomas, kidney cancers, eye cancers, and adrenal gland cancers are the most common cancers of children. In contrast, skin, prostate, breast, lung, and colorectal cancers are the most common in adults. The stage of growth and development is another important difference between adults and children. The immaturity of children's organ systems often has important effects on treatment.

What Are the Types of Childhood Cancers?

Leukemia
Leukemias are the most common childhood cancers. They account for about 33% of all childhood cancers. Acute lymphocytic leukemia (ALL) and acute myelogenous leukemia (AML) are the most common types of leukemia in children. Leukemia may be cause bone and joint pain, weakness, bleeding, fever, weight loss, and other symptoms.

Brain and nervous system cancers
Brain and other nervous system cancers are the second most common cancers in children, making up about 21% of childhood cancers. Most brain cancers of children involve the cerebellum or brain stem. In early stages they can cause headaches, nausea, vomiting, blurred or double vision, dizziness, and trouble walking or handling objects. Adults are more likely to develop cancers in different parts of the brain--usually the cerebral hemispheres. Spinal cord tumors are less common than brain tumors in both children and adults.

Neuroblastoma
Neuroblastoma is the most common solid tumor (besides brain tumors) in children. It is most often found during the first year of life. This tumor can start anywhere but usually occurs in the belly (abdomen) and is noticed as swelling. It can also cause bone pain and fever. It accounts for about 7% of childhood cancers.

Wilms tumor
Wilms tumor is a cancer that may affect one or both kidneys. It is most often found in children between 2 and 3 years old, and can show up as a swelling or lump in the belly (abdomen). Sometimes the child may have other symptoms, such as fever, pain, or poor appetite. Wilms tumor accounts for about 5% of childhood cancers.

Lymphoma
Non-Hodgkin lymphoma and Hodgkin lymphoma (sometimes called Hodgkin disease, Hodgkin's disease, or Hodgkin's lymphoma), are cancers that start in lymph tissues, such as the tonsils, lymph nodes, and thymus. These cancers may spread to bone marrow and other organs, which can cause different symptoms depending on where it is growing. They also can cause fever, sweats, weakness, and swollen lymph nodes in the neck, armpit, or groin.

Hodgkin lymphoma can occur in both children and adults, and accounts for about 4% of childhood cancers. It is more common, though, in 2 age groups: early adulthood (age 15 to 40, usually 25 to 30) and late adulthood (after age 55). Hodgkin lymphoma is rare in children younger than 5 years of age. About 10% to 15% of cases are diagnosed in children 16 years of age and younger.

Non-Hodgkin Lymphoma makes up a little more than 4% of childhood cancers, and can cause symptoms similar to Hodgkin lymphoma. It can also cause other symptoms depending on where it starts in the body.

Rhabdomyosarcoma
Rhabdomyosarcoma is the most common soft tissue sarcoma in children. It makes up a little more than 3% of childhood cancers. This tumor starts in the same embryonic cells that develop into striated (voluntary) muscles. It can happen in the head and neck, groin, abdomen, pelvis, arms and legs. It may cause pain, swelling (a lump), or both.

Retinoblastoma
Retinoblastoma is a cancer of the eye. It is rare, accounting for less than 3% of childhood cancers and about 5% of childhood blindness. It usually occurs in children under the age of 4.

Bone cancers
Primary bone cancers (cancers that start in the bones) occur most often in children and adolescents. Primary bone cancer is different from metastatic bone cancer, which is cancer that has spread from another site to the bone. Metastatic bone cancer is named for the place the cancer came from. For instance, it might be described as prostate cancer that has spread (metastasized) to the bone, or breast cancer with bone metastasis.

Metastatic bone cancer is more common than primary bone cancer because many types of cancer can spread to the bone. Two types of primary bone cancers occur in children:

• Osteosarcoma is uncommon, accounting for almost 3% of all new childhood cancer cases in the United States. It often causes no pain or symptoms until swelling starts, but sometimes there is worsening bone pain.
  Ewing sarcoma is a less common primary bone cancer which can cause bone pain. It occurs mostly in children and adolescents. It accounts for a little more than 1% of childhood cancers.

Can Childhood Cancer Be Prevented?

Unlike many cancers of adults, there are no avoidable risk factors (such as smoking or exposure to hazardous chemicals in the workplace) that are known to influence your child's risk of developing cancer. If your child does develop cancer, it is important to know that there is nothing you or your child did to cause it. Since a few childhood cancers can be hereditary, survivors of those types may want to think about genetic counseling before having children. This can help them understand the risks of passing the genetic defect onto their children and to explore ways to prevent that.

What are the Risk Factors and Causes of Childhood Cancer?

A risk factor is anything that changes your chance of getting a disease such as cancer. Different cancers have different risk factors. Lifestyle-related risks are thought to be the main factors that affect cancer risk cancers in adults. Examples include the effect of unhealthy diets (not eating enough fruits and vegetables, etc.), not enough exercise, and habits such as smoking and drinking alcohol. Lifestyle-related risk factors have little or no affect on childhood cancer.

Cancer is caused by a mutation (change) in a gene. During the past few years, scientists have made great progress in understanding how certain changes in a person's DNA can cause cells of the body to become cancer. DNA carries the instructions for nearly everything our cells do. We usually look like our parents because they are the source of our DNA. But DNA affects more than how we look. It also affects our risks for developing certain diseases, including some kinds of cancer. When children are born with mutated DNA that was inherited from parents, the mutations are present in every cell of the child's body. That means the mutations can be found by testing DNA of blood or other body cells.

Most cancers, though, are not caused by inherited DNA mutations. They are the result of DNA changes that happened early in the child's lifetime. Every time a cell prepares to divide into 2 new cells, it must copy its DNA. This process is not perfect, and errors sometimes occur. Luckily, cells have repair systems that "proofread" DNA. Some errors can still slip past, especially when the cells are growing quickly. This kind of gene mutation can happen at any time in life and is called an acquired mutation.

Acquired mutations start in one cell of the body, and that cell passes the mutation on to all the cells that come from it. These acquired mutations are present only in the patient's cancer cells and will not be passed on to his or her children. Although the causes of mutations responsible for certain adult cancers are known (for example, cancer-causing chemicals in cigarette smoke), the reasons for DNA changes that cause childhood cancers are not known. Some of these changes can take place in developing fetuses and are already present at birth.

Can Childhood Cancer Be Found Early?

Cancers in children often are difficult to recognize. Parents should be sure that their children have regular medical check-ups and watch for any unusual signs or symptoms that do not go away. These include an unusual lump or swelling; unexplained paleness and loss of energy; easy bruising; an ongoing pain in one area of the body; limping; unexplained fever or illness that doesn't go away; frequent headaches, often with vomiting; sudden eye or vision changes; and sudden unexplained weight loss. Although many adult cancers can be prevented by lifestyle changes that reduce certain risk factors, there is currently no known way to prevent most childhood cancers.

Children who are known to have a higher chance of developing cancer due to known genetic risks should get careful, regular medical check-ups.

How are Childhood Cancers Treated?

Childhood cancers can be treated with a combination of treatments that are chosen based on the type and stage of cancer. Treatment options may include chemotherapy, surgery, and/or radiation therapy. Although there are exceptions, childhood cancers tend to respond well to chemotherapy because they are cancers that grow fast. Most forms of chemotherapy affect only cells that are growing.

The cancer treatment team
Children with cancer and their families have special needs that can be best met by children's cancer centers. Treatment of childhood cancer in specialized centers is coordinated by a team of experts who know the differences between adult and childhood cancers, as well as the unique needs of children with cancers. This team usually includes pediatric oncologists, surgeons, radiation oncologists, pediatric oncology nurses, and nurse practitioners.

Childhood cancer treatment involves many professionals other than nurses and doctors, too. Children's cancer centers have psychologists, social workers, child life specialists, nutritionists, rehabilitation and physical therapists, and educators who can support and educate the entire family.

Surviving childhood cancer
Five-year survival rates vary a lot, depending on the type of cancer your child has. Overall, 5-year relative survival rates have improved greatly over the past 30 years, from less than 50% before the 1970s to nearly 80% today. This is largely due to new and improved treatments. The 5-year survival rate for neuroblastoma is 69%; brain and other nervous system, 74%; bone and joint, 72%; leukemia, 81%; Wilms tumor (kidney), 92%; Hodgkin lymphoma, 95%; and non-Hodgkin lymphoma, 87%.

The 5-year survival rate refers to the percentage of patients who live at least 5 years after their cancer is diagnosed. Five-year rates are used to give us a standard way of discussing prognosis (outlook for recovery and survival). Of course, many children live much longer than 5 years. Keep in mind that 5-year survival rates are based on patients who were diagnosed and treated more than 5 years ago. Improvements in treatment often result in a better outlook for patients diagnosed more recently.