Medical matters: Childhood cancer goes against a natural order

The Houston family has strong connections with Canada. Different types of Canadiana resonate chez nous: music, books, places of study. Unsurprisingly, crooner Michael Bublé is a favourite, with a concert attendance in Calgary some years back a particularly fond memory.

The news that Bublé’s three-year-old son, Noah, has been diagnosed with cancer is a shock. As is their right, the family have chosen not to specify the type of cancer the child has, beyond confirming he is being treated in the US.

We associate cancers in adults with increasing age and lifestyle factors; the absence of these risk factors, especially in younger children, adds to a feeling that childhood cancer goes against a natural order. This reinforces a sense of disbelief for parents at the time of diagnosis; the rarity of childhood cancer means it is not on our radar when a child becomes ill.

Some environmental factors, such as radiation exposure, have been linked with childhood cancers. A few studies have suggested that parental exposures (such as smoking) might increase a child’s risk of certain cancers, but more research is needed to reach a definite conclusion. But most childhood cancers have not been shown to have environmental causes.

A genetic cause seems the most likely trigger. Some genes control when our cells grow, divide into new cells, and die: genes that help cells grow or stay alive are called oncogenes; those that slow down cell division or cause cells to die at the right time are called tumour suppressor genes.

Childhood cancers may be caused by DNA changes that turn on oncogenes or turn off tumour suppressor genes.

Leukaemia (a cancer of the blood that begins in bone marrow), is the most common form of childhood cancer. It accounts for about a third of cases. It causes low levels of red blood cells, white blood cells and platelets, each of which produce specific symptoms. In the case of low red blood cells, a child might feel fatigued and dizzy, and may get short of breath. Low white blood cell counts leave children prone to repeated infection, and not having enough platelets leads to easy bruising, nosebleeds and bleeding gums.

In the sense that any cancer diagnosis can be good, leukaemia may not be worst. The most common form of leukaemia, acute lymphocytic leukaemia, has a survival rate of about 85 per cent, and the second-most common – acute myeloid leukaemia – has a rate between 60 and 80 per cent.

The second most common cancer in children and teenagers are tumours in the brain and spinal cord. Seizures can be the first sign of a brain tumour; this is usually due to raised pressure within the confined space of the skull. Symptoms to watch out for include persistent headache, nausea, blurred vision, and trouble maintaining balance.

Looking back over the symptoms and signs listed above, readers will be struck how common many of them are in children. The medical axiom “not all brain tumours cause headaches, and most headaches are not caused by tumours” is a reminder that most children with even persistent headaches will not be diagnosed with cancer. Infections are very common in children: most are caused by a virus which the immune system deals with as a matter of routine.

Similarly symptoms like swelling, bruising, pain, fever, and vision changes are more likely to be caused by something more benign than cancer. However their ubiquity means your doctor will not be thinking cancer, at least initially, when presented with these symptoms in a child.

A swelling in the tummy could be a sign of nephroblastoma (kidney), a less common form of childhood cancer. Wilm’s tumour, another form of kidney cancer, accounts for about 5 per cent of childhood tumours. Lymphomas (lymph glands) and sarcomas (bone and soft tissue) also occur in children.

Whatever type of cancer Noah Bublé has, here’s wishing him a speedy recovery.

mhouston@irishtimes.com

@mhouston