After decades of false dawns, scientists have become wary of claims of breakthroughs in the war on cancer. Yet the programme for this year's UAE Cancer Congress, which opens this week in Dubai, reflects a flickering new source of hope. On Friday, a special session is being devoted to immuno-oncology, an approach to treating cancer using the body's own disease-fighting immune system.
Drugs that boost its abilities or train it to attack cancer cells are proving astonishingly successful in treating some forms of the disease.
Patients once condemned to just a few months of life after diagnosis are now living for years, while some appear effectively free of the disease.
The idea that we have our own anti-cancer treatments within us isn’t entirely new. Since the time of the Ancient Egyptians, physicians have suspected that deliberately infecting tumours might provoke the body’s own defences to join in the fight and destroy the cancer.
The problem is that cancer cells aren’t foreign invaders but damaged normal cells proliferating out of control. As such, they are easily overlooked by the immune system.
This had led to research into ways of making the immune system more sensitive to the presence of cancer cells.
By the early 2000s, researchers had identified so-called monoclonal antibodies (mAbs) that home in on disease-fighting cells in the immune system, making them better able to detect molecules on the surface of cancer cells.
Known as immune checkpoint inhibitors, these drugs have been shown to help combat a wide range of cancers, including the most common form of lung cancer.
It was one such drug – Yervoy, for treating metastatic melanoma - that in 2011 became the first immunotherapy for cancer.
Other mAbs have been created that seek out cancer cells and mark them for the immune system to attack, like the laser beam on a sniper’s rifle. Some interfere with the parts of cancer cells that allow them to grow or spread. This is the mode of action of perhaps the most famous immunotherapeutic drug, Herceptin, used to treat breast cancer – the most common form of the disease among women in the UAE.
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Other strategies involve combining mAbs that work in different ways, or using them to boost the effectiveness of conventional treatment like chemotherapy.
The current excitement comes from the fact that when immunotherapy works, the outcome can be astonishing.
In the mid-2000s, metastatic skin cancer killed 85 per cent of patients within five years. Now, more than one in five who get a single treatment of Yervoy can expect to be alive in 10 years’ time. About three-quarters of breast cancer patients receiving Herceptin live for another decade or more.
But while research scientists race to find more ways of helping our bodies defeat the big C, cancer specialists in hospitals are having to wrestle with some stark realities.
First, immunotherapy just doesn’t work for the vast majority of patients.
Only about one in eight patients respond to Yervoy, while just 15 to 25 per cent of women with the disease have cancer cells vulnerable to Herceptin.
A recent analysis suggests that, in total, just one in 12 patients with the most common cancers can expect to get any benefit from current immunotherapeutic drugs.
Then there are the side-effects. Because they work by making the immune system more trigger-happy, immune checkpoint inhibitors like Yervoy come with a long list of side-effects, some of them life-threatening.
This has led to doctors holding back on prescribing the “wonder drugs”, for fear that they will work their magic but at too high a price.
Research is under way to tackle these problems. For example, Swiss drugmaker Roche has developed a blood test that determines the number of genetic mutations in a tumour. The more of these there are, the higher the chances of the cancer being susceptible to immunotherapy.
But the biggest barrier to the wider use of these drugs is far more basic: their cost.
A course of treatment with immunotherapy typically costs well in excess of US$100,000 (Dh367,290). One therapy recently approved by the US Food and Drug Administration for advanced or inoperable melanoma costs more than $250,000 a year.
And while a small minority of patients may be completely cured, most can expect to get perhaps a few extra months.
All this is putting the promise of immunotherapy beyond the reach of most who could benefit from it. Having health insurance is unlikely to make much difference, as it is likely to run out before treatment is completed.
For Emiratis, for whom cancer treatment is free, the cost issue is academic – for now. Government budgets are under pressure, and difficult questions may soon have to be asked about the cost-effectiveness of these drugs.
Unless pressure is put on Big Pharma to cut the costs, cancer immunotherapy will become a miracle cure only for those with the right genes and bank balance.
Robert Matthews is Visiting Professor of Science at Aston University, Birmingham, UK