Image copyright Kreena Dhiman Image caption Kreena didn't think she'd see her 40th birthday after having breast cancer and heart failure

"It's bonkers what's happened over the past five years," says Kreena Dhiman from Crawley in West Sussex.

When diagnosed with breast cancer in 2013 at 33, she had just settled back into working life after getting married and spending a year backpacking round the world.

"I noticed one of my nipples was inverted and when I Googled for answers, I thought: 'Oh God, this can't be me.'"

Three years later, after surgery to remove one breast, chemotherapy, radiotherapy and another major reconstructive operation, Kreena felt she was out of the woods.

She had even arranged to have some of her eggs harvested, so that embryos could be created and frozen in case the cancer treatment made her infertile.

But then on a trip to Canada "to celebrate the end of my life with cancer", she felt grim.

She was tired, her chest was tight and she was struggling to breathe. Hospital doctors were baffled, until one cardiologist made a crucial link.

"He told me to squeeze his hand if I remembered having a red liquid during chemotherapy treatment," Kreena recalls.

She did. The diagnosis was acute heart failure and she was rushed to intensive care.

Heart damage risk

Thanks to advances in treatments, more patients than ever are surviving cancer - but one in 10 are developing serious heart conditions, sometimes soon after finishing treatment, others years later.

The problem is caused by chemotherapy drugs damaging the heart muscle, meaning it can no longer pump properly - and this can lead to heart failure.

It's even given rise to a new medical specialty called cardio-oncology, which focuses on delivering cancer treatments safely.

But working out which patients will get heart damage, and which won't, has proved really tricky up until now.

Image copyright Getty Images Image caption Chemotherapy can be toxic to the heart muscle - but not everyone is affected

Scientists knew that the very young and the elderly were at high risk, but they've now found out that faulty genes also play a role in increasing risk in other people.

"Some have a gene to cause heart failure and they get a second hit from the chemo," explains Dr Alex Lyon, a consultant cardiologist at the Royal Brompton Hospital and Imperial College London.

"Most patients are told there's a small risk of heart problems."

A study of 200 cancer patients with cancer-therapy-induced cardiomyopathy, or CCM, by Imperial College London researchers has pinpointed the genetic risk factors, paving the way for testing of patients before they start chemotherapy to find out who is at risk.

The good news is that drug treatments can reduce the risk of heart damage in these patients and close monitoring can pick up potential problems early, Dr Lyon says.

'Pregnancy too dangerous'

Even patients like Kreena, who were left fighting for breath, can return to live a normal life.

"My recovery is incredible," she says. "I didn't think I'd be coming home."

Image copyright Getty Images

During two weeks in a Canadian hospital, she sent voice messages back to relatives, preparing them for the worst.

After a two-month stay in the country on a no-salt diet and being cared for by her husband, her heart function had improved from 6% to 12%.

It was enough to allow Kreena to fly back to the UK, but that was just the start of her journey to recovery.

Medication and intense rehab followed, which allowed her heart to creep back into a normal range of function.

But there was one thing she was told was too dangerous - having a baby would put too much strain on her heart.

"So we started to look at other options," she says.

'I'm very grateful'

A surrogate was found, and using her own embryos, her daughter was born and is now 16 months old.

"Next month, I'm climbing in the Himalayas. I'm living an extraordinary life and I'm very grateful," Kreena says.

"I thought I wouldn't see my 40th birthday, but now it's just two weeks away."

Her expedition is part of of push to raise awareness of breast cancer in young women from the charity Coppa Feel, a cause that's important to her.

"More people are surviving cancer after chemo and more are getting secondary diseases.

"There's work to do educating patients and doctors."