Our Science Surgery series answers your cancer science questions. 

One of our Instagram followers asked: ‘Does cancer affect the future development of children?’

“It massively depends on what cancer the child has, where it is and how it’s treated,” says Dr John Moppett, an expert in childhood blood cancer from the University of Bristol Hospitals NHS Trust.

Most children who’ve had cancer carry few major long-term side effects into adulthood. But when they do, the side effects will vary hugely depending on what treatment they’ve had.

Children usually recover after chemo

Thankfully, children’s cancer isn’t very common. The number of cancer cases in children aged 0 to 14 and  young people aged 15 to 24 each make up less than 1% of the total number of cancer cases diagnosed in the UK each year. Blood cancers, known as leukaemias, account for around one third of childhood cancer cases in the UK.

“In terms of leukaemia, the vast majority of treatment will have next to no long-term side effects on the child at all,” says Moppett. “Which means no effects on fertility, growth, intellectual capacity or anything really. The same can be said for many solid tumours in kids.”

Chemotherapy is normally the first option to treat these cancers. Despite being effective at killing cancer cells, these drugs are designed to kill any cell that divides, so can come with nasty side effects.

Damaged normal cells are great at replenishing themselves quickly once treatment has stopped. So, although horrible, these effects are relatively short-lived.

And for the times when chemo causes more severe, long-term damage like hearing loss, research is helping to find kinder solutions.

Minimising the long-term impact of more aggressive treatment

The future development of children with cancer is often more of a concern when chemo isn’t an option.

Take leukaemia for example, the children who are most likely to have complications are those needing an aggressive treatment called a bone marrow transplant.

For certain types of blood cancer, the treatment uses high doses of radiotherapy to destroy the child’s bone marrow and with it their cancer cells. But is also destroys other cells living in the bone marrow, which are replenished by new, transplanted cells.

It’s fairly rare for children to have this treatment – less than 5 in 100 children who are diagnosed with the most common type of leukaemia, acute lymphoblastic leukaemia (ALL),  and around a third of a less common leukaemia, acute myeloid leukaemia (AML),  need a bone marrow transplant. But it can have a big impact if they do.

“Whilst a transplant gives us the best chance of curing some children, it can affect their growth,” says Moppett. He explains that they can end up shorter than they would have done otherwise because their body can no longer make the hormones that help them grow.

Total body irradiation can also impact a child’s sexual development and fertility.

“Body radiation can upset a child’s hormone levels, and puberty can be delayed or never happen. But these are all things we would routinely track. And intervening with hormone injections or supplements is relatively simple.”

Moppett says research is also giving a lot of “hope” around preserving the fertility of young children with cancer and there are options available for teenagers and young adults with the disease.

Radiotherapy and development

“Brain tumours is the area where long-term effects can be quite different,” says Moppett. Treatment for brain tumours can vary treatment, but the one that are most cautious about is radiotherapy.

“Brain tumours that are in tricky places and need large doses of radiotherapy at a young age can affect the developing brain,” says Moppett.

And the younger you have it, the more likely it will affect development.

“We avoid radiotherapy as much as possible in children under three because research has shown that very young children who have radiotherapy to the brain are more likely to have changes to how their brain works after treatment,” says Moppett.

That’s because the central nervous system is not fully developed at three. And if the whole brain needs to be treated, areas controlling intelligence or the ability to learn can become irreversibly damaged and development stunted.

While these side effects won’t happen to everyone, doctors are more likely to give young children with brain tumours chemotherapy to keep their tumour under control until they’re old enough to have radiotherapy. And there are lo

As well as intellectual development, the brain is responsible for a plethora of delicate bodily functions, so radiotherapy can have some potentially surprising effects.

For example, girls who’ve had radiotherapy to the head can sometimes go through puberty early. Or if an area of the brain responsible for making growth hormones, called the pituitary gland, is damaged it can stop working and affect a child’s growth.

Research to reduce side effects

While these long-term side effects seem extremely worrying, the risk of each treatment needs to be weighed up against the benefits. And, thanks to research, the chances of people experiencing long-term effects from cancer treatment they had when they were young are becoming lower and lower.

For example, instead of a bone marrow transplant, children with hard-to-treat blood cancer may be able to have a form of personalised immunotherapy called CAR T cell therapy which may have less long-standing impact.

And a kinder type of radiotherapy called proton beam therapy is currently being put through trials to see if it’s as effective as current radiotherapy treatment with fewer long-term side effects.

What about school?

Dr Moppett says he’s always surprised at how quickly children catch up with their schoolwork and how keen they are to get back in the classroom.

“If children have to miss school for treatment, at the time it can feel like they’re missing out. But from my experience, in the big scheme of things they won’t suffer any long-term educational deficit, nor will their social development be affected.”

And for older children and young people who might need to take exams the support is there for them too.

“In that moment school is understandably very important for them but given the perspective of time the significance wanes.”

Gabi

If you’d like to ask us something, post a comment below or email sciencesurgery@cancer.org.uk with your question and first name.


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