PET/CT in paediatric oncology: clinical usefulness and dosimetric concerns

Abstract

Childhood cancer, always particularly distressing, appears to be on the increase. The last quarter of the last century saw an approximately 25% rise in the incidence of diagnoses of malignancies (all forms) in children in the Western world (USA and Europe), the figure rising from around 12 per 100,000 in 1975 to 15 per 100,000 in 2,000. This corresponds to an average annual increase of approximately 1% for the whole period. Among the major types of childhood cancer, leukaemias and cancers of the central nervous system account for more than half of all new cases. Around a third of childhood cancers are leukaemias, the most common type being acute lymphoblastic leukaemia. The most common solid tumours in children are brain tumours (e.g. gliomas and medulloblastomas), while other solid cancers (e.g. neuroblastomas, Wilms tumours, and sarcomas such as rhabdomyosarcoma and osteosarcoma) are less common [2]. Due to significant advances in treatment, however, the same 25-year period also saw substantial improvements in survival, with 5-year survival rates for all childhood cancers (combined) rising from around 55–60% to around 75–80% percent, the average annual increase for the whole period being approximately 5%. Of course, the data vary around these values in relation to age, gender, geography and type of cancer. In short, in the face of a growing incidence of childhood cancer cases, therapeutic advances seem to be failing to make inroads. But, in this scenario, there emerges a question: could application of today’s most advanced molecular imaging techniques help to boost the effectiveness of childhood cancer diagnosis and treatment? This is clearly a hypothesis worth addressing, but given that these techniques, such as positron emission tomography (PET), used alone or in combination with x-ray computed tomography (CT), are based on use of ionising radiation, it is also one that immediately raises the problem of potential radiation burden, known to be a much more critical issue in children than in adults. Indeed, because of concerns over radiation exposure, but also problems linked to long scan acquisition times and the need for sedation in young children, imaging studies in children tend to be restricted to patients in whom the study is absolutely crucial for the diagnosis, treatment planning and follow-up, when other modalities have failed to provide conclusive information. “Focus on...” abridgements aim to highlight papers published within the past year and draw extensively on the texts and summaries of the articles referenced. Less recent citations are also included when deemed useful to provide background information on the topic reviewed.