'Unthinkable' tragedy for family as father and toddler battle cancer at the same time

A cancer diagnosis can be a harrowing experience for any family. But for one family in the US, their worst nightmare has come true, with a father and his toddler daughter battling cancer at the same time.

And even more tragically, it comes after the family lost another child to cancer before they found out the cause: a rare genetic mutation.

"It's honestly unthinkable what one family has to go through," said the man's sister Madison in a video put together to support the family.

The family's troubles began in 2018 when Crosby Bowen was struck down with what his parents thought was a tummy bug just before he turned three.

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Nate and Allison Bowen took their son to the doctor, who thought he had a virus, but over the course of the next week, he became progressively sicker, Mr Bowen told TODAY.

The family decided to take Crosby to hospital, but on the way, he stopped breathing.

Once at hospital he was stabilised and moved to a children's hospital, where he died just 24 hours later. Doctors had discovered he had a large and very aggressive grade 4 brain tumour, glioblastoma.

"It was just very traumatic because it was so sudden," Mr Bowen said, adding it was just a month before his third birthday.

The family, which includes two other children, Dalton, now eight, and Tessa, now four, were left to grieve.

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After Crosby's death, the couple went on to have another child, Annabelle.

But at the end of 2020, they noticed a growing lump on her leg and took her to the same children's hospital where Crosby had died.

Doctors discovered a mass and Annabelle was eventually diagnosed with rhabdomyosarcoma, a soft tissue cancer affecting muscles.

In March 2021, doctors removed the tumor and she started chemotherapy, which is still continuing. Doctors also suggested genetic testing to see if there was a reason why the two siblings had developed cancer.

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"The doctors said, 'OK, this is your second child to get cancer. Let's test your genetics and figure this out'," Mr Bowen told TODAY.

"When you have multiple children that are young that have cancers, there's typically this genetic mutation often associated with it."

Tests showed Annabelle had a rare genetic condition called Li-Fraumeni syndrome, a mutation in the TP53 gene that prevents tumour growth. The syndrome increases the chance a child or young adult will develop cancer. It can either be passed down or occur spontaneously.

Further genetic tests revealed Mr Bowen also had the syndrome and he was advised to undergo regular cancer screenings. It was during a routine brain MRI in September last year that doctors discovered a large brain tumour.

"As you can imagine it was gut-wrenching," Mr Bowen's sister Madison revealed in an Instagram story. "It's still hard to even process how one family can be put through so much."

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Mr Bowen is hopeful it was caught early enough for a good outcome and is thankful the genetic testing uncovered his condition.

Tests showed his parents do not carry the mutation, meaning he developed it spontaneously before passing it down to Annabelle. It's likely Crosby had it as well, although they cannot be sure.

Thankfully, neither his wife or other children have the syndrome.

Mr Bowen had surgery to remove 90 per cent of the grade 2 astrocytoma. Doctors are holding off chemotherapy or radiotherapy because it could increase his chances of developing other types of cancer.

While he has recovered well from surgery, he said it was tough to have cancer treatment at the same time as his daughter, who spends a lot of time in hospital with her mother, whom Mr Bowen praised for her strength.

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He said cancer would always be part of their lives, through treatment, regular screenings and anxiety, with both he and Annabelle at greater risk of developing other types of cancer.

Despite their battles, including mounting medical costs, Mr Bowen said the family felt "blessed".

"There's been this outpouring of love that we hardly expected or anticipated," he said "We've been humbled and completely astounded."

Madison continues to share details of their battle on her Instagram page to help raise money for the family.

"We are just hoping 2022 is a little brighter," she said through tears.