Trying to get any four-year-old to do things that are good for them is a challenge that most parents will face.

From tooth brushing, to eating their vegetables, if it's not something that appeals to them in that moment, you have a battle on your hands. And in reality it's more than likely a battle that they'll win as you shelve the idea until another day.

But what do you when the thing they don't want any part of is the treatment that stands between them surviving cancer, or losing their life?

This is the heartbreaking predicament that Queensland couple, Angela and Marc Dickenson found themselves when their normally happy four-year-old son, Oscar was diagnosed with Burkitt lymphoma, a form of non-Hodgkin's lymphoma in which cancer starts in immune cells.

The cancer is recognised as the fastest-growing human tumour and is rapidly fatal if left untreated. And for Oscar, there were some days that treatment was just too much.

Marc Dickenson has taken on Townsville to Cairns 350km bike ride for four years in a row, in the hope that other children won't have to go through what his son, Oscar did.

In the hope of saving other families from going through the same trauma, Marc took up bike-riding in order to take on the Townsville to Cairns 350km bike ride to raise much needed funds into childhood cancers and their treatments.

Their brave story will both break your heart and warm it.

WATCH: Townsville to Cairns 350km bike ride for kids cancer. Post continues after video…

Angela and Marc were parents to seven-year-old Isla and four-year-old Oscar in October, 2015 when their entire world came crashing down.

A call from Oscar's kindy relayed that he'd had a sudden onset of vomiting and pain.

"He'd been fine, so this just came out of the blue," said Angela. "I didn't think too much of it, kids get bugs all the time, and he was fine by the time I picked him up."

For the following few days Oscar was generally feeling a little unwell, but nothing that would indicate they had an emergency on their hands.

"He was still eating and drinking, he was just a bit off," explains Angela.

Come Sunday morning, Oscar had developed a temperature, and upon the parent-check that we all do when our kids are a sick, Angela and Marc discovered a lump in his abdomen.

"We took him to the emergency department where he was diagnosed with appendicitis, which they would operate on," said Angela.

Oscar was originally diagnosed with appendicitis, however, the reality was much more frightening.

"When they went in, they discovered it was not appendicitis," says Angela. "There was a 20cm lump which they removed, however it was not until pathology came back that we were told what it actually was."

The Dickensons were told that their little boy had Burkitt lymphoma, a form of non-Hodgkin's lymphoma.

"It was terrifying, I was asking the doctor if it could be a mistake," says Angela. "It's the fastest growing human tumour, it can double in size very fast and it was inside my son."

While Oscar laid, ventilated, his family were told of the battle he now faced.

"The treatment was chemo, very intensive chemo because of the rapid growth of the tumour. We were to leave Townsville straight away and within 12 hours the whole family were flown to Brisbane to begin the fight."

See how you can help the Dickenson family raise much needed funds for childhood cancer research here.

At age four, Oscar had no idea what cancer was, he just knew it was frightening.

"You are at the mercy of hospital, you go do everything that they ask of you and hope that it works and that your child responds, because the reality is that it's not always successful," says Angela.

"We were so fortunate and grateful to have the Leukaemia Foundation who gave us somewhere to stay in Brisbane and helped us all through it all."

And if it was tough for his family, for Oscar being far from home and facing the fight of his life had him truly frightened.

"We'd never spoken to him about cancer," says Angela. "Why would we? He had no idea what was going on, and for the most part he was just so brave."

"We were honest with him, we told him what was happening, and he remained such a sweet happy little boy, through most of it, but towards the end of his last cycle of chemo, he had had enough, and that's when he first ran away."

Towards the end of the treatment, Oscar was over it, and ran away.

"He ran away from me between appointments," explains Angela.

It was getting towards the end of the treatment plan, but Oscar still had some cancer to fight. As Angela moved in between appointments in the hospital with Isla and Oscar in tow, Oscar made his escape, bolting out through the hospital doors and out to a main road.

"I had to leave Isla in the X-Ray department to go find him, it was a nightmare," says Angela.

There was no peace to be found when Oscar was located.

"It was heartbreaking, he was screaming, he didn't want to come back into the hospital, he didn't want anymore treatment. He was so frail, but still fighting and we had to force him back inside. He ended up covered in bruises from us trying to stop him from running away, but what could we do?"

Angela was crying, Isla was crying, Oscar was screaming. This is the reality of childhood cancer treatment.

"You can't just say, 'oh don't worry about it', we won't do it'" says Angela. "As much as you would do anything for them to not have to go through it."

And, sadly that wasn't the only time Oscar tried to escape his treatment.

"During a treatment in oncology he got out of bed and ran away," says Angela. "A male nurse had to physically drag him back in. It was traumatic, and he ended up with a massive infection and got very very sick."

"You would do anything for them to not have to go through it, but they have to."

Desperate for something tangible to do for his son, Marc considered the Townsville to Cairns 350km charity bike ride which was well-known in their home town.

"He wasn't a bike-rider," laughs Angela. "But he went out and got the bike and the gear and began riding early in the mornings.

"The first time he rode 15 kms he vomited! It was way tougher than he imagined, but he had to do something while Oscar was in treatment."

Marc, along with some friends, rode in Oscar's honour for the first time in July 2016.

"He's continued to do it every year and progressed each time into a faster rider group, all with the hope of raising money for cancer research," says Angela.

Oscar is now in remission, and Marc is determined to take on the Townsville to Cairns 350km bike ride in support of the Children's Cancer Institute for many years to come.

For Oscar, the gruelling treatment was worth it. After several months in the children's hospital he was declared in remission.

Now seven, Oscar is once again enjoying playing and being a normal little boy.

"He has six-monthly check-ups, and while he's not fond of his bloods being taken, he handles it all like the little champion he is!"

Read more about the Townsville to Cairns 350km bike ride here.