At the lowest point, when chemotherapy had turned Thomas van der Plaetsen bald and weak at 23, even his brother, coach and biggest fan, Michael, thought chances of a comeback were minuscule. Now, barely a year and a half later, he is heading to the Rio Olympics as the European decathlon champion and with a full head of hair.

Failing to get close to the medal stand at the Olympics will not feel anything like losing gold. Just being back among the best, participating in the Games, is already his biggest victory of all.

“It was a long road back,” the Belgian said. “If I can reach and convince only one person to stay positive in such a situation, I will take that as a victory.”

Even if life had already given him a few knocks – he lost his father to cancer at 20 – he was well on the way up in 2014 when he won a bronze medal at the World Indoor Championships.

Then, early that autumn, he received a letter at home from anti-doping authorities. It was notification that he had an abnormal test for the HCG hormone, which usually indicates doping in athletes. Before he had time to wrap his head around it, the Belgian media had caught wind of the test, and rumours were rife that yet another athlete was not what he promised to be.

However, Van der Plaetsen knew he had not doped and sought another explanation. It led him to testicular cancer.

For a man and athlete, both options were shocking, likely career-ending and life-changing. Yet, as a doping suspect, it forced him to make his illness, so utterly personal, a public issue within days.

“It was extremely painful,” he said. “To be put at the stake at such short notice when I could not defend myself is totally wrong.” There was little time to dwell on being wronged, though. There was an operation to remove the tumour, sapping sessions of chemotherapy to endure.

Three months later, he made his first appearance as an athlete again when he received Belgium’s “Golden Spike” as best athlete for his bronze at the World Indoor Championships the previous March. He decided to make a comeback. This is where his brother, Michael, came in. Not any coach can push a recovering cancer patient, but when it is your brother things are different. Michael took him on a training camp in South Africa. They set out with little medical guidance but one defining motto: “You cannot train on self-pity.”

Michael said: “You cannot moan and complain about it all the time. You need to forget and look ahead. Look for the little victories in life. It is the only way forward.”

Still, it was painful enough early on. What looked like a simple warmup left him exhausted. A good day would be followed by two bad days. With 10 running, jumping and throwing events, there was always something to cloud his mind. If it was not the javelin, it could be the 100m. He knew that the days when he could improve on sheer athleticism alone were gone.

“I was real tough on him, but he knew he had to get moving again,” Michael said. Thomas realised he had to fundamentally change to survive.

“The most important lesson is that I took a huge leap when it comes to skills,” said Thomas, honing his technical talents to make up for loss of raw power. “And I learned how to stay focused. There was no option. If I made one mistake, it was over and out. I was with my back against the wall, one error and it’s over. That is the biggest victory. I reinvented myself as an athlete to be able to get back at my level even despite the physical setbacks.”

Michael knew his brother thrived on championships. Despite the short deadline, he entered him to defend his World University Games title last summer. Against the odds, he did. There was a glimmer of hope, and the chance to become an Olympian now had a whiff of possibility. Still, it was a setback when he barely missed out on qualifying for Rio at last year’s world championships, where he came in 14th.

Van der Plaetsen’s elbow started acting up over the winter, a huge drawback for the javelin and shot put events. Qualifying had to be postponed until the European championships in Amsterdam in early July.

He came through, not only with the qualifying margin but also with a European gold medal. Yes, he was overjoyed, when thousands were cheering him. Yet, he knew some opposition had stayed away to prepare for Rio, and he was frustrated for falling short of his personal record of 8,255 points by 37 points in windy and chilly weather. “I won’t get lyrical about it, but it is simply good,” he said.

Michael now wants to see his brother beat his personal best in Rio. “Symbolically that would be great to close out the season with proof that he is better than ever before.”