For the Leeds youngster, facing a cancer battle at just 16, diagnosis and treatment was to impact on more than just his physical health.
Reliant on a Zimmer frame, and having gained five stone in weight through steroid treatment, his self-esteem had dipped to a terrible low.
"I just felt so ashamed, when I looked at myself," the now 25-year-old says.
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"I felt a burden, on everybody. I didn't ask for cancer and I needed the treatment - but people would look through me as if I wasn't there."
Mr Rumblow is speaking out today as part the Teenage Cancer Trust's #StillMe campaign, shining a light on the impact of the condition on body image and self-esteem.
Snap polls, carried by the charity, have found that the issue is one of great importance to young people facing a cancer diagnosis.
Of those polled, 23 per cent said they were worried about how their looks would be affected, compared to 21 per cent worried about painful and lengthy treatment.
Mr Rumblow's cancer journey had started at just 16 with a niggling joint pain, turning to a dull ache. Then the pain spread to his spine, small bumps appearing along his forehead.
Three times, his discomfort was dismissed as growing pains, anaemia, or even arthritis. But he was pale, short of breath, and struggling to walk cross a room.
His mother, ignoring doctors' advice, took the teenager to A&E.
"I didn't have a clue what was going on," says Mr Rumblow, from Morley, who spent five days undergoing tests only for it to emerge he had Acute Lymphoblastic Leukaemia.
"The doctor walked in and said 'you've got cancer'. It was as blunt, and as sharp as that. I was 16 years old. I just looked at my mum, and we both burst out crying.
"Had we waited just a few more days, I would have been blind and paralysed," he adds, revealing the lumps on his forehead were tumours, building behind his eyes and spine.
Mr Rumblow's strongest memory is of the moments that followed his diagnosis. Wearing checkered pyjama pants, he had sat with his mother on a bench outside St James' Hospital.
"I said 'mum, let's just run away, go anywhere other than here'," he recalls. "She turned and looked at me and said 'in those pants, you're not going anywhere'.
"I had been so scared, I thought I was going to die. As time went on, I thought I might as well face it. There's no point in being afraid."
The youngster was transferred to the Teenage Cancer Trust unit at LGI, where he would start his three years of treatment, including chemotherapy.
The cancer had eaten away at his pelvis, leaving it cratered with a 'honeycomb' effect. There were stress fractures in his spine, muscle wastage in his legs from being unable to stand.
One of the biggest challenges for Mr Rumblow was the way he felt about himself. Always a fit teenager, he gained five stone while on steroid treatment.
He couldn't walk, he couldn't get a glass of water without help. And through it all, he was losing his teenage years.
"With social media, I could see all my friends out partying, getting jobs," he says. "I was very angry and bitter, not at them but at the world.
"I was fighting for my life, but watching them live their best lives. I had a Zimmer frame at 16, or my mum had to wheel me around in a wheelchair."
Mr Rumblow's childhood dream had always been to join the Army, and there have been cases where survivors have been accepted after being cancer-free for more than five years.
This knowledge had given Mr Rumblow new hope, and he regained strength with the support of a sports therapist at the Teenage Cancer Trust.
He had to learn to walk again, then to run. In February, he reached five years cancer free. But despite flying through Army tests, he was deemed medically unfit because of his history.
While his ambitions for the Army were thwarted, he said, he comes away with the knowledge that this sense of ambition had seen him through the biggest fight of his life.
"I was so close, staring in the face of my dream," he says. "It was heartbreaking. For me, your dreams and your goals are who you are.
"I wouldn't change it for the world," he adds today. "The little things, like walking my first steps again, show me I've come so far.
"It's so important to have that dream, to have a goal. Because there is light at the end of the tunnel, and it does get better."
Teenage Cancer Trust
Every day, seven young people in the UK are diagnosed with cancer.
Kate Collins, chief executive of the Teenage Cancer Trust, said: “Over the past three decades we’ve supported thousands of young people like Terence through treatment, and we know changes in appearance can be distressing and tough to deal with.
“The 'ideal' bodies and looks portrayed on Instagram that many young people aspire to are difficult to live up to at the best of times - and the effects of cancer and treatment on appearance, like hair loss and weight gain, can really add to this pressure.
“People like Terence are sharing their experiences of how they coped, and this will do so much to help other people facing similar issues. We’re really proud and grateful that he is part of our #StillMe campaign.”