Seven years ago, when Heather Hall was informed by her oncologist that her kidney cancer had spread to the liver, she initially assumed she had just months to live. “I’d been on chemotherapy for a while, but they’d done a CT scan and found three new tumours,” she says. “But they then said that, because the tumours were relatively small, they could try to lengthen my prognosis by removing them with ablation.”
Hall underwent a course of microwave ablation, a minimally invasive treatment where specialists known as interventional radiologists use hollow needles to deliver intense, focused doses of radiation to heat each tumour until it is destroyed. While ablation technologies – they also commonly include radiofrequency ablation and cryoablation, which destroys tumours using intense cold – are not tackling the underlying cause of the disease, their impact can be enormous as they relieve pain and often prolong survival for many years, all at a low cost.
While there have been many breakthroughs in cancer treatment heralded by the media in recent years – most notably the advances in immunotherapy and combination therapies – the considerable advances in ablation technology and resulting impact on patient survival, have consistently slipped beneath the radar. Not so long ago, the only option for patients such as Hall would have been full or partial removal of an organ, greatly reducing quality of life. But now, with increasingly powerful and efficient devices, interventional radiologists are able to destroy drug-resistant tumours in a growing number of diseases ranging from sarcomas to prostate cancer.
A US interventional radiologist using a radiofrequency ablation probe. Photograph: Robert J Polett/Design Pics/Getty Images/Perspectives“When we were first using ablation we could only treat the simplest tumours – for example, the ones in the middle of the liver, away from the blood vessels, because the devices were less powerful and predictable,” says Matthew Callstrom, a professor of radiology at the Mayo Clinic, Minnesota. “But now, for example, with microwave ablation – which works by radiating an energy field out of the tip of the needle into the tumour, heating the water within the cancer cells until they are destroyed – you can tune the shape and diameter of that field to prescribe exactly how deep it goes into the tissue. This means we can safely go after more and more complex tumours.”
Major studies published in the past couple of years have confirmed the survival benefits. Last year, the results of the Clocc trial – a five-year study of 119 patients across 22 centres in Europe – showed that patients with colorectal cancer that had metastasised to the liver and who received ablation in addition to drug treatment lived significantly longer on average than those who received drugs alone.
“We work closely with oncologists to determine who is most likely to benefit from this and who isn’t,” says Andreas Adam, professor of interventional radiology at King’s College London. “But it can have huge benefits. For example, I had a patient with breast cancer that had spread to the liver. I ablated the tumours, destroyed them completely and every few months or years, another tumour would develop and I’d ablate again. She went on to live for almost 10 years.”
With ablation treatment allowing many patients to live for far longer, it has the potential to change the perspective on some diagnoses. Patients with metastatic disease who go on to live for another decade or more in relatively little discomfort, often come to view their condition as more like a chronic illness. “It’s a strange feeling because you are still living with an illness which is likely to be terminal sooner rather than later,” Hall says. “But it’s no longer in the forefront of your mind. I’ve even been able to return to work part-time.”
However, not every patient with metastatic disease is a suitable candidate for ablation. Interventional radiologists typically only use the technique on patients with 10 tumours or fewer. Any more, and the only viable options are treatments such as chemotherapy or immunotherapy. “You wouldn’t dream of ablating 50 tumours, because if someone has 50 visible tumours, it’s likely that they have another 100 developing that are not yet visible, and so they need drug treatment to treat the disseminated disease,” Adam says.
But in the coming years, ablation is likely to become available to more and more patients, allowing interventional radiologists to tackle cancers in ever more complex locations.
Among the most promising methods is a technology called irreversible electroporation, which involves electrodes being inserted through the skin into a tumour, allowing a high voltage to be generated across the cancer cell membranes, causing them to self-destruct. This is only offered by a small handful of specialised centres in the world, but is expected to become more widespread over the next decade. “It’s a non-thermal approach, so you can go into more sensitive areas such as the pancreas, or ablate tumours which are in the centre of the liver,” Callstrom says.
One day, interventional radiologists may even be able to ablate the most difficult cancers of all – deep brain tumours. The Israeli company Insightec is developing a device that can use focused ultrasound to destroy brain lesions. Because these tiny pulses of energy can be detected on MRI scanners, surgeons can calibrate them to the exact millimetre. “Each pulse generates a single ablation the size of a grain of rice,” Callstrom says. “Because it’s so tiny this allows you to basically tattoo the tumour and so avoid the boundary to any blood vessels or neurons.”
So for the many patients who have cancer that doesn’t respond to any form of drug treatment, there is now often a way of managing and prolonging their lives, which wasn’t possible before.
“The results of these studies have completely changed the thinking regarding some cancers,” Callstrom says. “With patients with metastatic sarcomas, for instance, people used to think that if the drugs failed, that was that. But now we can monitor them. And every time new tumours pop up, we ablate them.”
• This article was amended on 7 August 2018 to make clear that microwave ablation treatment is conducted by interventional radiologists, rather than surgeons.