Why do some cancers come back? Here’s what the scientists tell us

Professor Nick Turner, consultant medical oncologist at the Royal Marsden NHS Trust, and professor of molecular oncology at the Institute of Cancer Research, says: “Early diagnosis of breast cancer is key to decreasing the risk of cancer spreading, as small cancers have a really excellent chance of being cured. But sadly, even if you catch it early, that doesn’t mean it can’t spread. With most cancers, if you get to five years without relapsing you are cured, but the risk from breast cancer can last for at least 20 years. This is partly because oestrogen breast cancers [which need oestrogen to enlarge] grow slowly so it can take many years to reach a point where they are detectable. But we also know this type of cell is more likely to go into this dormant stage.”

A study last year found that oestrogen-sensitive breast cancers, which account for 80 per cent of diagnoses, can come back up to 32 years after the initial diagnosis, a point at which most women would consider themselves cured.

Metastatic disease is also widely misunderstood. A US study found that 72 per cent of people believed advanced breast cancer was curable. And women with the disease often feel ignored by fundraising campaigns and stigmatised as not having taken proper care of themselves or having missed screening appointments. But when Newton-John’s cancer was first diagnosed in 1992, it couldn’t even be seen on her regular mammogram. Yet it still returned decades later.

Improvements in treatments mean that women diagnosed with breast cancer today are half as likely to die of it as those treated 30 years ago.

Scientists around the world are starting to unravel the mystery of how and why cancer cells spread, create new ways to diagnose and treat metastatic cancer earlier than ever, and maybe even prevent it. In the US, the Fred Hutchinson Cancer Center has received a new, four-year, $25 million grant from the US Department of Defence to learn, as the centre puts it, “how to kill metastatic cancer’s deadly seeds before they can sprout”.

Breast cancer researcher Dr Cyrus Ghajar said: “We have to move the needle on metastasis. But we’re not going to be able to do that until we understand the biology of dormancy, and you’re not going to do that until you start looking closely at these cells and how they’re regulated.”

In the UK, Prof Turner says: “There have been big advances which mean at the time of diagnosis we are better at calculating which patients are at higher risk of recurrence, and this guides treatment. In future, we are looking at blood tests known as “liquid biopsies” which can pick up tiny amounts of cancer DNA in the blood. These could be used both to reassure women at low risk and to spot the very earliest stages of relapse. Patients could then be given treatments that might defer or even prevent relapse.”

Better drugs given after surgery and chemotherapy also play a role in reducing the risk of recurrence. In April, Nice approved a new drug, Enhertu, for patients with HER2-positive metastatic breast cancer. In trials, Enhertu more than doubled survival time compared to the previous best treatment. Trials are now testing Enhertu in women with HER2-positive early breast cancer for whom immunotherapy and chemotherapy did not eradicate the disease entirely, in the hope it will prevent recurrence.

Personalised medicine is, says Natrajan, the future. “With Single Cell Sequencing, we now have the ability to look at the DNA in every single cancer cell in a tumour and look at a cellular level at why they aren’t responding to treatments.” This could enable people to move on to more effective treatments more quickly.

Labs around the world are also working on vaccines against cancer. These, says Turner, may be used in future in two ways, “firstly – and this is the most optimistic – to vaccinate healthy people so they are less likely to develop cancer; secondly, in patients who have had cancer, to enhance the immune system to clear any bits of cancer that have somehow escaped the main tumour and systemic treatment”.

However, he adds that the benefits to patients in the near future are less likely to come from “a big step” but from “small, incremental progression developing new drugs that work a little better than the previous ones. We have every reason to expect that the progress we’ve made in the last 30 years will continue.”

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Turner says: “There is genuine optimism that we are understanding the genomics [DNA] of cancer better, including understanding the role the immune system plays in cancer’s resistance to treatment. In 10 years’ time, maybe 85-90 per cent of women will be cured of breast cancer.”

And the hope is that even for patients with metastatic cancer, improvements in treatment will mean it can become a chronic condition, rather than a lethal one.

The Telegraph, London

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