PAE506 — Paediatric Oncology: Lecture Note

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la-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS

la-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Course code: PAE 506 Course title: Paediatric Oncology Course credit load: 2 Units Series 1: Epidemiology and Risk Factors of Childhood Cancer • Part 1.1: Age-Related Incidence of Childhood Cancer o Sub Part 1.1.1: General epidemiology of childhood cancer o Sub Part 1.1.2: Age-related incidence patterns o Sub Part 1.1.3: The clinical significance of age-related incidence • Part 1.2: Race-Related Incidence and Genetic Factors o Sub Part 1.2.1: Race-related incidence patterns o Sub Part 1.2.2: Genetic factors in childhood cancer causation o Sub Part 1.2.3: Genetic syndromes associated with increased cancer risk • Part 1.3: Chemical-Related Factors o Sub Part 1.3.1: Chemical exposures and childhood cancer risk o Sub Part 1.3.2: Specific chemical associations o Sub Part 1.3.3: Challenges in establishing chemical causation • Part 1.4: Environmental Factors o Sub Part 1.4.1: Ionising radiation and childhood cancer risk o Sub Part 1.4.2: Infectious and other environmental associations o Sub Part 1.4.3: The interplay of epidemiological and risk factors Introduction Picture a five year old brought to clinic with unexplained fevers, pallor, and easy bruising over several weeks, findings that, while common to many childhood illnesses, occasionally point towards an underlying malignancy. Childhood cancer, though far less common than cancer in adults, remains an important cause of childhood death, and understanding its epidemiology and the factors that increase risk provides the essential foundation for recognising, diagnosing, and managing the specific tumours discussed later in this PAE 506 course.

la-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS The aim of this Series is to equip you with an understanding of the epidemiology of childhood cancer, including age- and race-related incidence patterns, and the genetic, chemical, and environmental factors associated with increased risk. This Series begins with the age-related incidence of childhood cancer, before turning to race-related incidence and genetic factors. Next, we examine chemical-related factors, before concluding with environmental factors associated with childhood cancer. Series Learning Outcomes At the end of this Series, you should be able to: • SLO 1.1: describe the general epidemiology of childhood cancer, • SLO 1.2: describe the age-related incidence pattern of childhood cancer, • SLO 1.3: describe the race-related incidence pattern of childhood cancer, • SLO 1.4: describe the genetic factors associated with childhood cancer, • SLO 1.5: list the genetic syndromes associated with increased childhood cancer risk, • SLO 1.6: describe the chemical factors associated with childhood cancer, • SLO 1.7: describe the environmental factors associated with childhood cancer, and • SLO 1.8: discuss the interplay of epidemiological and risk factors in childhood cancer causation. 1.1 Age-Related Incidence of Childhood Cancer 1.1.1 general epidemiology of childhood cancer Rare overall, but a significant cause of childhood death Childhood cancer is considerably rarer than cancer in adults, accounting for a relatively small proportion of the overall global cancer burden, yet remains an important cause of childhood morbidity and mortality, since malignancy is among the leading causes of death in children beyond infancy in many settings, once the most common infectious and nutritional causes of death have been addressed through improved public health measures. Unlike the great majority of adult cancers, which are predominantly carcinomas arising from epithelial tissue and often linked to cumulative lifestyle exposures over many years, childhood cancers are more often embryonal tumours, leukaemias, and lymphomas, reflecting the distinct developmental and biological origins of malignancy in this age group, a distinction

la-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS with important implications for understanding both causation and the specific tumour types discussed later in this course. Fill in the blank: Childhood cancers are more often embryonal tumours, leukaemias, and ________. 1.1.2 age-related incidence patterns The incidence of specific childhood cancers varies considerably by age, with certain tumours showing a characteristic peak incidence within a particular, relatively narrow age range, reflecting their embryonal origin, since these tumours arise from cells that retain developmental potential most actively during specific periods of fetal and early postnatal life, before this potential is normally lost as tissues mature. Embryonal tumours, including neuroblastoma, nephroblastoma, and retinoblastoma, discussed in detail in later Series of this course, characteristically present in infancy and early childhood, often before 5 years of age, while other tumours, such as Hodgkin's lymphoma, show a different age pattern, becoming relatively more common in later childhood and adolescence, illustrating how age at presentation itself provides an important diagnostic clue. Fill in the blank: Embryonal tumours characteristically present in infancy and early childhood, often before ________ years of age. 1.1.3 the clinical significance of age-related incidence Understanding age-related incidence patterns is clinically valuable, since the age of a child presenting with a mass, organomegaly, or other feature suggestive of malignancy directly informs the differential diagnosis, with a very young child presenting with an abdominal mass, for example, appropriately raising greater suspicion for neuroblastoma or nephroblastoma than for a tumour type more typical of older children or adolescents. This principle of using age as a diagnostic clue applies broadly across paediatric oncology, and will be revisited repeatedly across the tumour-specific Series later in this course, since recognising the expected age range for a specific tumour, alongside its other characteristic clinical features, meaningfully narrows the differential diagnosis and helps guide the initial diagnostic evaluation of a child with a suspected malignancy. Fill in the blank: Understanding age-related incidence patterns directly informs the ________ diagnosis of a child with a suspicious presentation.

la-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Figure 1.1: A paediatric oncologist speaking with a family during a clinic consultation. Pilot questions 1.1 1. Describe how childhood cancer differs from adult cancer in overall frequency and typical tumour type. (Linked to SLO 1.1) 2. Explain why embryonal tumours characteristically present in infancy and early childhood. (Linked to SLO 1.2) 3. List three embryonal tumours discussed later in this course. (Linked to SLO 1.2) 4. Describe the age pattern of Hodgkin’s lymphoma compared with embryonal tumours. (Linked to SLO 1.2) 5. Explain how age at presentation informs the differential diagnosis of a child with a suspected malignancy. (Linked to SLO 1.2) 1.2 Race-Related Incidence and Genetic Factors 1.2.1 race-related incidence patterns Some tumours show striking geographic and population differences Certain childhood cancers show notable variation in incidence according to race and geographic region, with Burkitt's lymphoma, discussed in detail in the next Series of this

la-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS course, showing a particularly striking example of this pattern, occurring at a considerably higher incidence in equatorial Africa, where it is closely associated with Epstein-Barr virus infection and malaria, compared with its incidence in other parts of the world, where it occurs sporadically and at a much lower frequency. Other tumours also show recognised variation in incidence between different population groups, though the underlying reasons for these differences are often multifactorial, reflecting a genuine combination of genetic susceptibility, differing patterns of environmental exposure, and, in some cases, differences in diagnostic capacity and reporting between regions, meaning race-related incidence data should be interpreted with appropriate caution rather than assuming a purely genetic explanation in every instance. Fill in the blank: Burkitt’s lymphoma occurs at a considerably higher incidence in equatorial ________. 1.2.2 genetic factors in childhood cancer causation Genetic factors contribute to childhood cancer risk through several mechanisms, including inherited germline mutations in specific tumour suppressor genes or oncogenes, which predispose an affected child to developing a specific cancer, sometimes at a considerably younger age or with multiple, bilateral tumours compared with children who develop the same cancer type without an underlying inherited predisposition. A well recognised example is the inherited form of retinoblastoma, discussed in detail in a later Series of this course, resulting from a germline mutation in the RB1 tumour suppressor gene, which not only increases the risk of retinoblastoma itself, often presenting bilaterally and at a younger age, but also confers an increased lifelong risk of certain other malignancies, illustrating how a single genetic predisposition can have implications extending well beyond the initial childhood cancer diagnosis. Fill in the blank: Inherited retinoblastoma results from a germline mutation in the ________ tumour suppressor gene. 1.2.3 genetic syndromes associated with increased cancer risk Several recognised genetic syndromes carry an increased risk of specific childhood cancers, including Li-Fraumeni syndrome, associated with a broad range of malignancies including sarcomas and early-onset breast cancer later in life, Beckwith-Wiedemann syndrome, associated with increased risk of nephroblastoma and hepatoblastoma, and Down syndrome, associated with an increased risk of leukaemia, illustrating the diversity of genetic conditions relevant to paediatric oncology risk.

la-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Recognising these associations is clinically valuable, since children with a known genetic syndrome carrying increased cancer risk may benefit from structured surveillance programmes, allowing earlier detection of a malignancy should one develop, and genetic counselling, discussed in an earlier course, plays

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