Tumours in genetic syndromes

Epidemiological studies show that children are much more sensitive to the effect of radiation than adults and may develop severe toxicity and a higher incidence of secondary radiation-induced tumours. In addition to the oncology therapies received to treat the primary tumour at a young age, other factors such as genetic susceptibility to neoplasms caused by a mutation of a tumour suppressor gene may contribute to the development of secondary tumours in children.

The most frequent genetic syndromes that place a child at risk of tumours are:  Retinoblastoma (RB) caused by a mutation in the RB1 tumour suppression gene, Li-Fraumeni Syndrome  (LFS) caused by mutations in the p53 gene, Neurofibromatosis type 1 (F1) associated with mutations in the NF1 gene, and Nevoid basal-cell carcinoma syndrome (NBCCS) caused by mutations in the PTCH gene. These are just a few examples recognized as a substantial risk for the development of secondary tumours for genetic susceptibility and greater sensitivity to radiation.

Retinoblastoma

Several studies show there is an association of the development of secondary tumours and radiation therapy in paediatric patients affected by retinoblastoma, a rare predisposing illness that affects about 3% of all paediatric tumours. It can arise in two forms: hereditary, when a germline mutation of the RB1 gene is present at birth (generally affects both eyes) and sporadic, if acquired during childhood (almost always involving just one eye). The hereditary form predisposes the individual to a series of new tumours and radiation therapy emphasizes the phenomenon, promoting the development of secondary tumours at the side of the previous radiation.

Li-Fraumeni Syndrome

This is a dominant hereditary syndrome caused by a germline mutation in the p53 tumour suppression gene characterized by the precocious development of mammary tumours, sarcomas, brain tumours, adrenocortical tumours, and acute leukaemia. The risk of developing a tumour is approximately 50% at 30 years of age and 90% at 60 years of age.

Neurofibromatosis type 1      

This is a dominant hereditary autosomal disorder that predisposes the individual to the occurrence of new tumours caused by a mutation in the NF1 gene. Children who are NF1 carriers are at risk of developing peripheral malignant tumours of nerve sheaths, leukaemia, and gliomas. For this reason, the use of radiation therapy must be carefully evaluated in patients who are NF1 carriers, especially if children, due to the high risk of developing new secondary tumours in the radiation location.

Nevoid basal-cell carcinoma syndrome (NBCCS)

NBCCS, also called Gorlin Syndrome, is a rare, dominant autosomal disorder characterized by the development of multiple basal cell carcinomas, mandibular cysts, and skeletal abnormalities. Children with this syndrome have a very high risk of precocious development of multiple basal cell carcinomas in the radiation location (from 6 months to three years after radiation therapy ended). Plus, NBCCS predisposes the individual to development a very aggressive tumour in the central nervous system called a medulloblastoma that involves 20% of brain tumours during childhood.

These are just a few examples recognized as a substantial risk for the development of secondary tumours for their genetic susceptibility and greater sensitivity to radiation.

The use of protons as a radiation therapy technique in patients with these syndromes and with active oncological illnesses offers greater savings in irradiating the healthy tissue surrounding the tumour region. In this way it is possible to reduce the incidence of late toxicity and radiation-induced tumours in subsequent years.