The treatment, which succeeded after all other conventional treatments had failed, marks the first successful application of T-cell immunotherapy for late-stage breast cancer.
While the technique is still in its early days, scientists have welcomed its potential as a future treatment for cancers that have resisted all other forms of therapy.
Judy Perkins, a 49-year-old engineer from Florida, was selected to undergo the cutting edge treatment after several chemotherapy sessions had failed to kill the tumour, which had begun to spread to her liver. Before the new treatment, doctors had given her three years to live.
She was treated by a team led by Dr Steven Rosenberg at the National Cancer Institute (NCI) in Maryland.
The clinical trial, which is still ongoing, used modified T-cells – which make up part the body’s immune response – to tackle the patient’s tumours.
Doctors caring for Ms Perkins during her recovery described her return to health as "remarkable". She has now been entirely free of cancer for two years.
Immunotherapy, which involves stimulating the body’s natural defences to fight cancer, is already being used to tackle certain cancers, and some forms are already available on the NHS.
However, the response rate to even the most successful treatments is relatively low, with one recently trialled therapy showing strong effects in only around 10 per cent of prostate cancer patients.
Previous clinical trials using immunotherapy to treat breast cancer have proved largely ineffective.
The new approach pioneered by Dr Rosenberg and his team was based on an existing technique called adoptive cell transfer that has proved effective when treating melanoma, but not other forms of the disease.
Cancer specialists have described the news as significant evidence that this new approach to immunotherapy could succeed where others have failed.
“This research is experimental right now,” said Dr Rosenberg.
“But because this new approach to immunotherapy is dependent on mutations, not on cancer type, it is in a sense a blueprint we can use for the treatment of many types of cancer.”
The NCI team’s method involved taking T-cells that specifically target cell mutations within patients’ tumours. These cells were then grown in large numbers in the lab and infused back into the patient.
To treat the patient in this trial, Dr Rosenberg and his colleagues sequenced genetic material from one of her tumours to identify mutations that were specific to her case.
They then used this information to pinpoint the T-cells capable of targeting those mutations.
The results of this work were published in the journal Nature Medicine.
Professor Alan Melcher, an immunotherapy expert at the Institute of Cancer Research, said this “exciting” study showed “a remarkable success in terms of translating our basic biological understanding of how the immune system responds to cancer into a real treatment of real benefit for this particular woman”.
However, he noted the treatment would probably not work for everyone, and that further successful trials will be necessary before it can be rolled out widely.
“The actual feasibility, not to mention the cost of it, has not been addressed – but the excitement is around the proof of principle,” Professor Melcher, who was not involved in the research, told The Independent.
“This is an area in which the technology is moving so quickly that things that seem impractical at the moment in very few years’ time may well be deliverable.”
Other experts agreed that while these initial results would need to be confirmed in larger clinical trials, they hold promise for a variety of particularly stubborn forms of cancer.
“This is another piece of evidence confirming that some cancers are recognisable by the body’s immune system and that if this can be stimulated in the right way, even cancers that have spread to different parts of the body may be treatable,” said Professor Peter Johnson of the Cancer Research UK Centre at Southampton General Hospital.
“This is an illustrative case report that highlights, once again, the power of immunotherapy,” said Dr Tom Misteli, director of the NCI’s Centre for Cancer Research.
“If confirmed in a larger study, it promises to further extend the reach of this T-cell therapy to a broader spectrum of cancers.”
In an article commenting on the results of Dr Rosenberg’s trial, Dr Laszlo Radvanyi of the Ontario Institute for Cancer Research said they provided evidence that “we are now at the cusp of a major revolution” in cancer immunotherapy.
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