What’s more, this success rate was seen in patients who were expected to live only months because such conventional cancer treatments as chemotherapy had failed to save them.
The results are being hailed as amazing and, if the trial’s success can be replicated on a much larger scale, could prove a pivotal moment in the history of cancer treatment.
Scientists at the Fred Hutchinson Cancer Research Centre in Seattle are claiming the medical victory after they treated several dozen patients with a cancer of the white blood cells called acute lymphoblastic leukaemia (ALL).
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Normally, only 40 percent of patients aged between 25 and 64 survive for five years after being diagnosed with ALL.
The rate is even lower among people aged 65 or older, at a dismal 15 percent, according to Cancer Research UK.
The American scientists’ new therapy involves genetically modifying a key weapon in the patients’ natural immune defence system, called T-cells.
These normally hunt and kill cells in our bodies that are infected with bacteria, or such viruses as cold and flu.
Crucially, the genetic modification effectively teaches the T-cells to recognise cancer cells as enemies to be destroyed.
As well as seeing the 94 percent success rate in ALL patients, when the researchers tried the treatment – called immunotherapy – on people with other blood cancers, they improved the condition of more than 80 percent of patients.
In more than half of those patients, the cancer appeared to have gone completely. As one of the lead investigators, oncologist Dr Stanley Riddell, says: “This is unprecedented in medicine, to be honest, to get response rates in this range in patients with these very advanced cancers.”
One further hope is that these “trained” T-cells will be able to stay in the body for years – acting as a form of vaccination against any returning cancers.
Another new immunotherapy study indicates that such modified T-cells can stay in the body for at least 14 years.
Professor Chiara Bonin says that her research at a Milan hospital demonstrates that it is possible to create cells that still “remember the cancer and are ready for when it comes back”.
Seasoned cancer experts are not ready to break out the champagne just yet, however, because the past two decades have seen many new therapies hailed as “magic bullets” for cancer subsequently not living up to their promise.
This is because they have cured far fewer patients than was first hoped or their side effects have proved too dreadful to inflict on patients.
In fact, one of the first scientists to use immunotherapy to fight cancer was New York surgeon William Coley in the 1890s.
He was inspired to do this by a patient with a rare cancer who staged an unexpected recovery after suffering a serious bacterial infection.
Coley believed this infection had provoked the patient’s immune system to attack anything that looked alien, including the cancer cells.
He then began vaccinating other cancer patients with bacteria, believing that, in a minority of cases, this spurred the immune system to destroy tumours.
His work was greeted with scepticism, however, and was then overtaken by the development of radiotherapy and chemotherapy as powerful cancer treatments – if not without their side-effects.
Now, William Coley’s ideas are being explored anew, but attempts to develop immunotherapy into a modern anti-cancer weapon have been dogged by the fact that tinkering with the human immune system is still fraught with danger.
These perils were highlighted in 2006, when six volunteers were admitted to Northwick Park Hospital in Middlesex after the disastrous trial of a drug that worked by modifying the immune system, and which was intended to treat such diseases as multiple sclerosis.
The six healthy young men’s immune systems began attacking their own bodies. They were rushed into intensive care with organ failure after experiencing serious reactions within hours of taking the drug.
The worst-affected lost his fingers and toes. What’s more, all the men were then told that they would be likely to develop cancers or auto-immune diseases as a result of their exposure to the drug.
Dr Riddell is open about the potential dangers of his newly-announced immunotherapy treatment: “There are reasons to be optimistic, there are reasons to be pessimistic.”
Indeed, during his trial, there were problems with some patients whose immune systems appear to have overreacted; 20 developed a condition called cytokine release syndrome.
Cytokines are messenger cells in the immune system that can go out of control when the system is overstimulated.
In turn, they can drive the immune system to overreact further, inflaming healthy cells throughout the body.
In Dr Riddell’s trials, the affected patients suffered symptoms of fever, dangerously plummeting blood pressure and nerve damage. Two of his patients died.
Dr Riddell believes, however, that lowering the dose of T-cells can reduce the risk of side effects.
There are other reasons why we should welcome such work with some caution, particularly since the results are very recent and there is a risk that the patients’ symptoms could reappear in future.
Indeed, cancers are notorious for returning months and even years after patients have been given the all-clear. This is not least because tumour cells can hide, dormant, deep in patients’ tissues to evade attack, and reactivate themselves later.
Professor Peter Openshaw, British Society for Immunology president, says that Dr Riddell’s research is “exciting” but believes we must be patient as its findings are explored further.
Intriguingly, he believes that, although this latest research used immunotherapy as a last-ditch treatment, it may best be used early on, just after patients have been diagnosed with their cancer.
The professor has also warned that immunotherapy may not work on many types of cancer, because the tumour cells they produce do not carry consistent identifying markers that the genetically modified T-cells can recognise and then attack.
Instead, the cells are able to change and adapt to threats.
“Such cancers can evade and escape immunotherapy by evolving their cells very quickly,” says Professor Openshaw.
Certainly, the tests causing so much excitement so far have targeted only certain blood cancers, and the researchers acknowledge they need to see how long their patients remain in remission.
It will also take at least five years to get this treatment into standard use.
Dr Riddell agrees immunotherapy requires much further development and that, even then, it will not be a panacea for every cancer. Nevertheless, his excitement is undimmed.
“Much like chemotherapy and radiotherapy, it’s not going to be a save-all,” he says. “However, I think immunotherapy has finally made it to becoming a pillar of cancer therapy.”
And for that, we may be both hopeful and grateful.