When Rachel Bown was diagnosed with stage four bowel cancer – the worst stage – she was eager to find a way to make sense of the ensuing chaos and distract herself, and so began writing lists.

Those lists, which range from a record of typical reactions to the shock of a cancer diagnosis, to one suggesting ways to tell the children, and a list of things you can and can’t do when you have cancer (you can sleep when you want, watch what you want on TV and say what you want, but you can’t easily get affordable travel insurance), helped Rachel so much that now, nearly three years on, they’ve been turned into a book, laced together with her cancer experience.

The C List has been published to coincide with April’s Bowel Cancer Awareness Month, which aims to draw more attention to this form of the disease – the second-biggest killer of all cancers. Every year, more than 40,000 people are diagnosed with bowel cancer in the UK and it kills nearly 16,000.

While the majority of cases are in older people, the number of younger people getting bowel cancer is rising In 2010 there were 2,018 under-50s diagnosed with it, compared with 1,698 in 1999.

Mother-of-two Rachel, 45, was one of them, and her book details how she was referred to a specialist and diagnosed in 2011, after visiting her GP three times with symptoms including abdominal pain, a change in bowel movements, blood in her faeces, weight loss and extreme tiredness.

The symptoms were initially passed off as the very common condition irritable bowel syndrome (IBS).

“I don’t know how long I’d had symptoms before I went to the doctor,” she says. “All I can say is that I was busy and I just pushed it to the back of my mind. I self-diagnosed and thought it was IBS.

“Yes, I could’ve gone to the doctor earlier, but I could’ve pushed them a lot more and not taken no for an answer if I’d been better educated in the symptoms and my risk. But because I didn’t know those things, I accepted it, twice.

“It’s embarrassing having to discuss your bowel habits, and if you get fobbed off, or reassured that it’s nothing, you grab it.”

The delay in her diagnosis is perhaps all the more surprising because a few years earlier her aunt had died from bowel cancer, aged 50, having been diagnosed a year before – and it’s recognised that genes can be a risk factor for the disease.

Bowel Cancer UK says genetic factors contribute to up to 30 per cent of cases, affecting 8,000-12,000 people, and those with a genetic link are likely to develop the disease much younger – as Rachel and her aunt did.

By the time Rachel’s cancer was detected, the tumour in her bowel had already spread to her liver and lymph nodes. She says her chances of survival were akin to the probability of “going over Niagara Falls in a barrel” and living to tell the tale.

“The cancer was so advanced, I just thought that was it, I had about six months,” she says.

“It was a real shock, but it’s amazing how much you can get your head around quite quickly. When you’re under that amount of pressure, every hour counts. I’m unbelievably lucky to still be here.”

Rachel, a marketing director, puts some of that “luck” down to the great medical treatment in her area – although she says bowel cancer treatment is a postcode lottery and the “inequality of care” worries her deeply.

“I feel massively grateful that I’ve had such good treatment,” she says, “but I also feel so upset for those who haven’t been able to have such good treatment. It just feels so wrong.

“You’re living with a time bomb, and it’s a horrible feeling.”

But after nearly three years, five lots of major surgery, eight months of “horrendous” chemotherapy and a relapse in her liver, she’s now in remission – and is looking forward to getting married to a man she met six weeks before her relapse last year.

The C List is published by Watkins, priced £10.99.