Radiotherapy is a medical treatment that uses high doses of radiation to kill or damage cancer cells. It is a common part of the treatment plan for many types of cancers, including pediatric tumors. The goal of radiotherapy is to target and destroy cancer cells while minimizing damage to surrounding healthy tissues. As childhood cancers are complex, and multi-disciplinary care is needed, there are international groups to help organise treatments. Large groups include the Children’s Oncology Group ( COG), Society International Oncology Pediatric (SIOP) etc. Treatment protocols help to keep management standardised. In Singapore, the Children’s Cancer Foundation helps families and patients through their treatments and beyond.

Pediatric cancers are broadly classified into 3 main types: Central nervous system, extra-CNS solid tumours and leukemias. Radiotherapy can be given for curative or palliative intentions. For curative treatments, proton therapy may reduce long term side effects by minimizing radiation doses to adjacent organs.

Common types of solid tumours:

1. Lymphoma:
   • Radiotherapy can be used as part of the treatment for Hodgkin lymphoma in children, particularly if the disease is not responding well to chemotherapy.
2. Wilms Tumor (Nephroblastoma):
   • This is a kidney cancer that primarily affects children. Depending on the stage and risk factors, radiotherapy may be used in addition to surgery and chemotherapy.
3. Neuroblastoma:
   • Neuroblastoma is a cancer that arises from nerve cells and commonly affects young children. Radiotherapy may be employed, particularly in high-risk cases or when the tumor is difficult to completely remove through surgery.
4. Ewing Sarcoma:
   • Ewing sarcoma is a type of bone cancer that can occur in children and adolescents. Radiotherapy may be used in conjunction with surgery and chemotherapy, depending on the location and extent of the tumor. For unresectable tumours, definitive radiotherapy can be used without surgery.
5. Rhabdomyosarcoma:
   • This is a soft tissue cancer that can develop in various parts of the body, including muscles. The use of radiotherapy depends on the tumor’s location and the extent of surgical resection. For unresectable tumours, radiotherapy can be used as the only tool for local control. For patients with metastatic disease, radiotherapy can also be used for control.
6. Retinoblastoma:
   • Retinoblastoma is an eye cancer that primarily affects young children. Radiotherapy may be considered in cases where other treatments, such as laser therapy or surgery, are not sufficient.

Common types of central nervous system tumours are

1. Medulloblastoma:
   • Medulloblastoma is one of the most common malignant brain tumors in children. It usually occurs in the cerebellum, the part of the brain that controls balance and coordination. Patient often require surgery, cranio-spinal irradiation and chemotherapy. Proton therapy can help to minimize radiation dose to healthy organs anterior to the backbone.
2. Ependymoma:
   • Ependymomas are tumors that arise from the cells lining the ventricles of the brain and the central canal of the spinal cord. They can occur at any age but are more common in young children. Radiotherapy to the tumour bed is required for local control.
3. Astrocytoma:
   • Astrocytomas are tumors that arise from astrocytes, a type of glial cell that provides support to nerve cells. They can be low-grade (less aggressive) or high-grade (more aggressive).
4. Low grade Glioma:
   • Gliomas are tumors that originate from glial cells, which are supportive cells in the brain. They include astrocytomas and oligodendrogliomas. Surgery and systemic treatment are usually first-line. For slow-growing asymptomatic tumours, observation is also appropriate. Radiotherapy is used when there are minimal options left, or when the tumours are sight-threatening.
5. Brainstem Glioma:
   • This type of glioma occurs in the brainstem, which is a critical part of the brain that controls many basic functions. Brainstem gliomas can be challenging to treat due to their location. When there is a particular mutation known as H3k27m, these tumours can be very aggressive. Palliative radiotherapy can help.
6. Craniopharyngioma:
   • Craniopharyngiomas are tumors that develop near the pituitary gland, which plays a crucial role in hormone regulation. They can affect vision and other functions. A combination of surgery and radiotherapy are appropriate.
7. Optic Pathway Glioma:
   • These tumors arise in or near the optic nerves, which can impact vision. They are often associated with neurofibromatosis type 1 (NF1)
8. Choroid Plexus Tumor:
   • Choroid plexus tumors can develop in the choroid plexus, which produces cerebrospinal fluid. They can be benign or malignant.
9. Spinal Cord Tumors:
   • Tumors can also develop in the spinal cord itself, such as ependymomas, astrocytomas, and other types.

The process of radiotherapy for pediatric tumors involves several key steps:

1. Treatment Planning:
   • Before starting radiotherapy, a comprehensive treatment plan is developed. This involves precise imaging techniques such as CT scans, MRIs, or PET scans to locate the tumor and surrounding structures.
   • Radiation oncologists work with medical physicists and dosimetrists to determine the appropriate dose of radiation and the optimal angles for delivering it.
2. Simulation:
   • During simulation, the patient undergoes a session to map out the treatment area. This may involve using immobilization devices to help the child remain still during treatment.
   • Special markings or tattoos may be made on the skin to ensure accurate positioning during each treatment session.
3. Treatment Delivery:
   • Pediatric patients may receive radiotherapy using external beam radiation or internal radiation (brachytherapy), depending on the type and location of the tumor.
   • External beam radiation is the most common method, where a machine directs a beam of radiation at the tumor from outside the body. The child does not feel the radiation during the treatment.
4. Fractionation:
   • Pediatric tumors are often treated with fractionated radiation, which means the total dose is divided into smaller, manageable doses given over several sessions. This helps minimize damage to healthy tissues while maximizing the effect on cancer cells.
5. Side Effects:
   • Side effects of radiotherapy for pediatric tumors can vary depending on the type of cancer, the location of the tumor, and the radiation dose.
   • Common side effects may include fatigue, skin irritation, nausea, and changes in blood counts. These will resolve after radiotherapy.
   • Long term side effects are dependent on which area of the body received radiation. Secondary cancers due to ioning radiation is also a concern. Children may experience unique side effects, and their healthcare team will closely monitor and manage these effects.
6. Follow-up Care:
   • After completing radiotherapy, pediatric cancer patients will be regularly monitored for any signs of recurrence or long-term side effects. Follow-up care may involve imaging studies and other medical assessments.
7. Multidisciplinary Approach:
   • The treatment of pediatric tumors often involves a multidisciplinary team, including pediatric oncologists, radiation oncologists, surgeons, nurses, and other specialists. This collaborative approach ensures that the child receives comprehensive care tailored to their specific needs.

It’s important to note that the treatment approach may vary for different types of pediatric tumors, and the decision on the use of radiotherapy is made based on the specific characteristics of the cancer, its stage, and the overall health of the child. The healthcare team will discuss the potential benefits and risks of radiotherapy with the child’s family to make informed treatment decisions.