41  General Principles

41.1 Introduction

Paediatric oncology is the branch of medicine that deals with the diagnosis, treatment, and long-term follow-up of cancers in children and adolescents. Although cancer is less common in children compared to adults, it remains a significant cause of morbidity and mortality worldwide. In many low- and middle-income countries, including those in sub-Saharan Africa, paediatric cancers are increasingly recognised due to improved awareness and diagnostic facilities.

Understanding the general principles of paediatric oncology is essential for medical students, as it forms the foundation for appreciating the biology, clinical behaviour, and management of childhood cancers.

41.2 Epidemiology of Childhood Cancers

• Childhood cancers account for about 1–4% of all cancers worldwide.
  
• The incidence is approximately 100–150 cases per million children per year.
  
• In high-income countries, survival rates exceed 80%, but in low- and middle-income regions, survival may be 20–40% due to late presentation, limited resources, and treatment abandonment.
  
• The most common paediatric cancers include:
  • Leukaemias (especially acute lymphoblastic leukaemia).
    
  • Brain tumours (medulloblastoma, astrocytoma).
    
  • Lymphomas (Burkitt’s lymphoma, Hodgkin lymphoma).
    
  • Solid tumours (Wilms’ tumour, neuroblastoma, retinoblastoma).

41.3 Biology of Childhood Cancers

Unlike adult cancers, childhood malignancies:
- Often arise from embryonal tissues or primitive cells rather than epithelial tissues.
- Show fewer environmental associations (e.g., smoking, alcohol, carcinogens).
- Are more commonly associated with genetic predispositions (e.g., RB1 mutations in retinoblastoma, TP53 in Li-Fraumeni syndrome).
- Tend to have rapid growth rates, making them highly responsive to chemotherapy and radiotherapy.

41.4 Clinical Presentation

Children with cancer may present with vague, non-specific symptoms that mimic common infections. High suspicion is necessary.

41.4.1 General warning signs of cancer in children (commonly remembered by the acronym CHILD CANCER):

• Continued, unexplained weight loss.
  
• Headaches with early morning vomiting.
  
• Increased swelling or pain in bones/joints.
  
• Lump or mass in abdomen, chest, or neck.
  
• Development of excessive bruising, bleeding, or rash.
  
• Constant infections.
  
• A whitish glow in the eye (leukocoria).
  
• Neurological symptoms (seizures, persistent dizziness).
  
• Changes in vision.
  
• Enlarged lymph nodes or persistent fever.
  
• Recurrent unexplained fevers.

41.5 Diagnosis and Staging

Diagnosis of childhood cancer requires a multidisciplinary approach.

1. Clinical evaluation – thorough history and examination, with attention to family history of cancers or syndromes.
   
2. Laboratory tests – complete blood count, peripheral smear, biochemical markers (e.g., LDH, uric acid).
   
3. Imaging – X-rays, ultrasound, CT, MRI, and PET scans depending on tumour location.
   
4. Histopathology – biopsy for tissue diagnosis (except for retinoblastoma where clinical diagnosis is usually made).
   
5. Molecular and cytogenetic studies – identification of chromosomal translocations (e.g., t(8;14) in Burkitt’s lymphoma, t(12;21) in ALL).
   
6. Staging – determines the extent of disease, using systems like:
   • Ann Arbor staging for lymphomas.
     
   • INSS (International Neuroblastoma Staging System).
     
   • TNM classification for some solid tumours.

41.6 Principles of Treatment

Treatment is multidisciplinary, involving oncologists, surgeons, radiation oncologists, pathologists, radiologists, nurses, and psychosocial support teams.

41.6.1 1. Surgery

• Plays a key role in diagnosis (biopsy) and treatment (resection of tumour).
  
• Examples: nephrectomy in Wilms’ tumour, enucleation in advanced retinoblastoma.

41.6.2 2. Chemotherapy

• Mainstay of treatment for most paediatric cancers.
  
• Uses cytotoxic drugs targeting rapidly dividing cells.
  
• Often given in cycles to allow normal tissues to recover.
  
• Commonly used agents: vincristine, doxorubicin, cyclophosphamide, methotrexate, cytarabine.
  
• Side effects: bone marrow suppression, alopecia, nausea, infections.

41.6.3 3. Radiotherapy

• Used in selected cancers (e.g., brain tumours, Hodgkin lymphoma).
  
• Careful dosing required to avoid long-term growth and developmental complications.
  
• Increasingly replaced by more precise modalities such as proton therapy where available.

41.6.4 4. Stem Cell Transplantation

• Indicated in high-risk or relapsed cases (e.g., relapsed leukaemia).
  
• May involve autologous or allogeneic transplantation.

41.6.5 5. Targeted Therapy and Immunotherapy

• Monoclonal antibodies (e.g., rituximab in B-cell lymphomas).
  
• Tyrosine kinase inhibitors (e.g., imatinib in Philadelphia chromosome-positive ALL).
  
• CAR-T cell therapy emerging in refractory cases.

41.7 Supportive Care

Equally important as definitive treatment, supportive care ensures the child tolerates therapy.

• Infection prevention and treatment: use of antibiotics, antifungals, and sometimes prophylaxis.
  
• Blood product support: transfusions for anaemia and thrombocytopenia.
  
• Nutritional support: maintaining adequate nutrition to aid recovery.
  
• Pain management: opioids and adjuvants as required.
  
• Psychological support: counselling for child and family.
  
• Management of treatment complications: tumour lysis syndrome, neutropenic sepsis.

41.8 Emergency Presentations in Paediatric Oncology

Certain cancer-related emergencies require immediate recognition and intervention:
- Febrile neutropenia – life-threatening infection during chemotherapy-induced immunosuppression.
- Tumour lysis syndrome – rapid cell breakdown causing hyperkalaemia, hyperuricaemia, renal failure.
- Mediastinal mass – airway compression in lymphomas or leukaemia.
- Spinal cord compression – neuroblastoma or vertebral metastases.
- Severe anaemia or bleeding – marrow infiltration by leukaemia.

41.9 Long-Term Follow-Up and Survivorship

With improved survival, focus has shifted to long-term outcomes:
- Late effects of therapy:
- Growth retardation from cranial irradiation.
- Cardiomyopathy from anthracyclines.
- Infertility from alkylating agents.
- Secondary malignancies.
- Rehabilitation and reintegration: ensuring schooling and social development.
- Psychological support: addressing anxiety, depression, and stigma.

41.10 Prevention and Early Detection

• Unlike adult cancers, primary prevention is limited in childhood cancers.
  
• However, measures include:
  • Avoiding unnecessary exposure to ionising radiation in pregnancy and childhood.
    
  • Vaccination against viruses that can indirectly influence cancer risk (e.g., HBV to reduce hepatocellular carcinoma).
    
  • Screening in high-risk families with known cancer syndromes (e.g., RB1 mutation carriers).
    
• Public health education on early signs of cancer is vital in improving outcomes in low-resource settings.

41.11 Prognosis

• Prognosis depends on:
  • Type of cancer.
    
  • Stage at diagnosis.
    
  • Response to therapy.
    
  • Availability of supportive care.
    
• Survival is excellent in conditions like Hodgkin lymphoma (>90%) but poorer in advanced neuroblastoma or late-presenting retinoblastoma.

41.12 Conclusion

Paediatric oncology integrates principles of cell biology, clinical medicine, and multidisciplinary care. While outcomes have improved remarkably in high-resource settings, challenges remain in low- and middle-income countries, where late presentation and limited infrastructure hinder survival. For medical students, an appreciation of the unique biology, presentation, and management of childhood cancers is essential in recognising cases early, guiding families, and contributing to improved outcomes in resource-constrained environments.