Professor Bernadette Brennan, Consultant Paediatric Oncologist, tells us what rare childhood cancers are and how they are treated.
What is a rare cancer?
Firstly, we need to put into context what we mean by a ‘rare cancer’ in childhood. This is because childhood cancers can be seen as rare in the general population accounting for less than 1% of cancers across all ages. The incidence of cancer in children (0–14-year-olds) is currently 1,645 cases per year compared with 375,000 cases per year of all cancers in the UK.
The most common cancers in children are leukaemia, brain tumours and lymphomas, and these have long-established trials and treatment guidance which have evolved over many decades through research and clinical practice. This level of focus has not been available for many rare childhood cancers, therefore there is very little information from prospective trials or collected patient data.
However, we are now seeing more international effort in producing treatment guidance and new registries for rare cancers based on the best available evidence. Therefore, there are now many more resources on how to best treat these cancers.
Types of rare cancers in children
Rare cancers in children can broadly be grouped as:
- rare cancers that only affect children, such as pancreatoblastoma, malignant rhabdoid tumours and melanotic neuroectodermal tumours of infancy
- cancers that usually only affect adults, such as cancers of the digestive system, the thyroid and the adrenal gland
- rare cancers in the head and neck area, such as nasopharyngeal cancer
- rare hormonal or endocrine cancers, such as phaeochromocytoma
- rare brain tumours, such as meningioma
- rare skin cancers, such as melanomas
Causes
The causes of most rare childhood cancers are unknown. But, if other family members have had particular types of cancer, this may sometimes suggest there is an inherited faulty gene within the family.
Rare cancers that only occur in childhood
Some rare cancers only occur in childhood, a good example of which are malignant rhabdoid tumours. Much work has been done in this cancer over the last 10 years to find out more about its specific cells, pattern of disease and tumour site. By collaborating internationally, more prospective trials and establishment of international guidance and registries have developed. Patients have also benefited from drug trials with specific targeted drugs with remarkable responses giving hope for future trials and better outcomes.
This particular type of rare cancer lends itself to the concept of ‘ask an expert’. This means that if a medical team is unsure on how to manage a patient with a rare tumour, there is always a wide network of UK and international experts who can be consulted. CCLG has led the national effort to produce clinical treatment guidelines for the diagnosis and management of over 20 rare cancers, which are regularly reviewed and updated. This network of experts has much clinical experience in the management of these rare cancers and indeed providing guidance in their management.
Importantly, in the UK we have the National Cancer and Registration and Analysis Service (NCRAS) which records the incidence, survival, prevalence and mortality for all cancers in childhood, and hence provides the baseline data for building these CCLG consensus guidelines. It also gives encouraging data so that the survival of children with melanoma, as an example, is over 90%. Internationally, the EXPeRT group of European countries including the UK has produced consensus guidelines for rare cancers, implemented a website (raretumours-children.eu) and have established a virtual tumour board (VTB) to help medical teams discuss the best management of patients with a rare cancer. This VTB has been established in an international setting that includes
experts with outstanding expertise. Lastly, they have produced patient information which is freely available about rare cancers on their website so parents and patients can understand better.
Rare childhood cancers that commonly occur in adults
Many adult cancers occur very infrequently in children as these are often related to age and lifestyle factors such as diet, smoking and sun exposure. Good examples are bowel cancer and a type of skin cancer called melanoma. If a child is diagnosed with a cancer usually seen in adults, the management of these tumours is often guided by adult clinical practice and evidence. However, these cancers are biologically different in children, behave differently and, while environmental factors play a definite role in the development of these cancers in adults, the timelines are too short in children so genetic factors may be important – not necessarily inherited but a new genetic change within the cells of the child with cancer.
Like other cancers in childhood, if a child is diagnosed with a particular type of rare cancer then this can be a defining indicator of a genetic condition, either inherited or only happening in the child. A good example is a type of adrenal gland cancer called ‘phaeochromocytoma’ which, even if there is no family history of other cancers in family members, indicates a referral to the genetics team. This is important as if an underlying genetic cause is found, this could lead to a set of screening studies to detect other cancers at an early stage and hence successful treatment.
An example of an adult cancer rarely occurring in children is melanoma, which can happen in children with an abnormal mole and usually behaves less aggressively than melanomas occurring in adults. They are usually managed with surgery after which there is surveillance only. In adults, melanoma needs more invasive treatment as it spreads more easily.
Final message
A rare cancer diagnosis in a child can cause much distress for the child and family as there is often a perception that if it is rare then no one knows how to treat it, and the child will do badly. We now know this is untrue, and much effort and success has happened over the last 10 years to provide national and international consensus on their management. This network of experts within the paediatric oncology community means we now have lots of advice and support on how to treat children with rare cancers.
We are now seeing more international effort in producing treatment guidance and new registries for rare cancers based on the best available evidence. Therefore, there are now many more resources on how to best treat these cancers.
From Contact magazine issue 98 - Spring 2023
