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More than half of patients can now survive a deadly skin cancer that was considered intractable just a decade ago, doctors in the UK say.
Ten years ago, only one in 20 patients would live for five years after the diagnosis of advanced melanoma. Most would die in months.
But drugs to control the body's immune system mean 52 percent now live for at least five years, a clinical trial shows.
Doctors said it was an extraordinary and rapid change in care.
How difficult is melanoma treatment?
Melanoma is the fifth most common cancer. in the United Kingdom and kills almost 2,300 people a year.
If detected in the early stages, chances of survival are good, but as cancer becomes more aggressive and spreads throughout the body (known as metastatic cancer), survival drops.
"In the past, metastatic melanoma was considered intractable," said Professor James Larkin, consultant for the Royal Marsden NHS Foundation Trust.
He said: "Oncologists considered melanoma different from other cancers. It cannot be treated after it has spread."
People tended to live between six and nine months after diagnosis.
What did the judgment show?
The study investigated two immunotherapy drugs designed to boost the immune system and allow it to attack cancer.
There were 945 patients in the study, one third received nivolumab, one third received ipilimumab and one third both.
Doctors looked at the five-year survival rate – the proportion of patients still alive after five years.
The results showed:
- 26% were still alive with ipilimumab alone
- 44% were still alive with nivolumab alone
- and 52% were still alive when they received both.
"It was an amazing surprise to see so much progress in such a short time," Larkin told BBC News.
He said: "It was the most extraordinary transformation of a disease that was considered, among all cancers, as the most difficult to treat, the most serious prognosis.
He said that now "there is a possibility that 50% of people with stage four melanoma will be alive five years after treatment with immunotherapy."
The findings were presented at a meeting of the European Society of Medical Oncology and published in the New England Journal of Medicine.
What do patients say?
Pam Smith: "Maybe I Didn't See My Grandchildren"
Pam Smith, 67, from Royal Tunbridge Wells, commenced trial in January 2014.
She was "devastated" when told that her cancer was intractable and said she "would have no chance" without immunotherapy.
She was treated once every two weeks for four months, but the medications caused diarrhea as severe as a side effect that she could no longer continue.
His tumor has halved after treatment and has not grown since. Pam now feels "brilliant".
She told the BBC: "Maybe I didn't see my grandchildren.
"It's been just over five years since it happened and my youngest grandson was six over the weekend.
"I wouldn't look like he grew up and the other grandchildren either."
Are these patients healed?
Saying healed is always difficult in cancer, but five-year survival is an extremely significant milestone.
Some patients taking the drugs are in complete remission, with no sign of any abnormalities in the scan.
Others like Pam still have a tumor inside their bodies, but they are no longer growing.
Of the surviving patients, three quarters no longer need any form of cancer treatment.
How does immunotherapy work?
Immunotherapy is the Nobel Prize-winning science that is making treatment intractable.
The field is one of the most exciting in cancer treatment.
The immune system constantly patrols our body, fighting hostile invaders like viruses.
It should also attack cancers – but cancers are a corrupted version of healthy tissue and can develop ways to bypass the immune system.
A corrupted cancer cell will grow out of control unlike its healthy neighbors
Ipilimumab and nivolumab prevent the hiding of some cancers and allow the immune system to attack.
They interrupt the chemical signals that cancer uses to trigger the immune system.
Nivolumab blocks the shutdown of white blood cells called PD-1. Ipilimumab blocks a similar switch called CTLA-4.
It is described as taking the brakes off the immune system.
"By administering these drugs, you effectively take two brakes out of the immune system, rather than one, so that the immune system is able to recognize previously unrecognized tumors, react to them and destroy them," Larkin said.
Are there any side effects?
Yes, medications are changing the way the immune system works within the body and this can have consequences such as fatigue, rash and diarrhea.
Some are severe enough that patients like Pam cannot complete a full course of treatment.
However, even a brief period of immunotherapy had a lasting benefit on the immune system and patients.
This is in stark contrast to other cancer treatments, such as chemotherapy, which stop working the moment treatment stops.
While these lasting changes mean side effects, they may continue to emerge as patients age.
Are these medications available?
Yes, previous results from this test have led to the availability of these drugs worldwide – including the UK National Health Service.
The decision to approve melanoma drugs was one of the fastest in NHS history.
And they are also being used in other cancers such as lung and kidney.
What do the experts think?
Charles Swanton, chief clinician at Cancer Research UK, said progress in melanoma was "incredibly fast."
He said: "I am inspired to see the advances being made in the development of immunotherapies and their potential to transform the perspective of some patients by giving them time with friends and family that they never thought they would have."
"And now work continues to ensure that more people with different types of cancer can also benefit from these innovative treatments."
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