‘Beyond the limit of detection’: Why breast cancer comes back

For five years, Kylie Minogue kept her second cancer diagnosis to herself. But her situation is far from uncommon – up to 30 per cent of women diagnosed with breast cancer experience a relapse.

Minogue first battled breast cancer in 2005, aged 36. “I was misdiagnosed initially,” Minogue told US talk show host Ellen DeGeneres at the time. “So my message to all of you and everyone at home is, because someone is in a white coat and using big medical instruments, doesn’t necessarily mean they’re right.”

The announcement led to “the Kylie effect”, a 101 per cent increase in women booking in for breast screening. Following a partial mastectomy, chemotherapy and radiotherapy Minogue was pronounced cancer-free in 2006.

However, cancer was again detected at a routine check-up in 2021, she reveals in a new Netflix documentary.

“I don’t feel obliged to tell the world,” the now 57-year-old said. “And actually, I couldn’t at the time because I was just a shell of a person.”

She has not publicly revealed what type of cancer she was diagnosed with, but about one in seven women in Australia will develop breast cancer, and the most common type is estrogen receptor-positive (ER+) breast cancer, which accounts for 70 to 80 per cent of cases.

Why people relapse

New research published in Nature Communications helps to explain why breast cancer can recur even many years after successful treatment.

It is known that cancer cells can lie dormant and then eventually “wake up” again, causing metastasis.

However, the new research reveals that sometimes the cells don’t become dormant, they just “really, really slow down” explains UNSW Conjoint Associate Professor Liz Caldon, lab head at the Garvan Institute.

Standard treatments target fast-growing cancer cells, allowing these extremely slow-growing cells to survive.

“They remain beyond the limit of detection of things like scans and then it’s only when you get enough of them there that the recurrence is finally detected,” says Caldon, the senior author of the study.

Minogue said that early detection saved her. “Thankfully, I got through it. Again. And all is well. Hey, who knows what’s around the corner?”

She may be one of the lucky ones.

How cancer relapses differ

“When someone gets a recurrence with ER-positive breast cancer, the disease is quite tricky to treat,” says Caldon. “For a significant proportion of women, it does need long-term treatment, and it can progress.”

Typically, treatment the second-time round is different, she says. “When a cancer comes back, it’s because it’s evaded the drugs. That’s why it’s less able to be treated in the long term.”

The slow growth rate of the cells does not limit the cancer’s ability to spread throughout the body, so symptoms may or may not show up in the breast.

Symptoms include new lumps or changes to the size, shape or skin of the breast; chest or lymph node pain; as well as pain in the bones or other parts of the body that doesn’t go away.

And because the cells are slow-growing, there may not be symptoms for a long time.

Confronting as the possibility of recurrence is, Caldon says the new research opens up the possibility of new, more effective treatments.

She also points out that the five-year survival rate from breast cancer is more than 90 per cent.

Eating a healthy diet, being physically active and staying at a healthy weight all help to minimise the possibility of recurrence.

“With the amount of research and the increase in understanding of the disease, we’re in a place now where we’re only going to get better outcomes in the future,” she says.

National Breast Cancer Foundation chief executive Dr Cleola Anderiesz agrees.

“We know many people live with the constant fear of wondering if their breast cancer could come back,” says Anderiesz, who discusses the latest research in an upcoming documentary, Conquering Breast Cancer.

“Developing more effective ways of determining if breast cancer will progress or recur in the breast or other parts of the body – and improving methods to halt its progression or recurrence – is fundamental to achieving the National Breast Cancer Foundation’s vision of zero deaths from breast cancer.”

Minogue, meanwhile, reminds people of the importance of check-ups. “It can be daunting and triggering, but please be mindful of just how vital they are – and reach out for help if you need it; you’re not alone.”

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