Immunotherapy, a medical procedure that uses antibodies cloned in laboratories to fight cancer, is emerging as a possible solution to treating and curing the disease that kills more than 8 million people worldwide every year.
A number of local and international studies that have been researching this procedure are showing positive results in terms of treatment and survival of cancer patients. However, oncologists are warning that it is too early to rejoice.
Speaking in Cape Town on Friday, Dr Daniel Vorobiof, director of the Sandton Oncology Centre in Johannesburg, said that, while immunotherapy was showing promising results, it would take some time before oncologists could safely say that this was the solution to cancer treatment and possible cure.
“We are seeing exciting clinical evidence from a number of studies. But we still have a lot of work to do in this regard,” he emphasised.
“What we know right now is that immunotherapy boosts the body’s own immune response to destroy cancer cells. This treatment also has fewer side-effects than conventional chemotherapy, which works by poisoning the cancerous cells,” he said.
Immunotherapy is an active area of cancer research. Scientists and doctors around the world have been studying ways to use immunotherapy to treat cancer for years.
It works by activating and boosting the body’s own immune response system, which will then destroy cancer cells. The immune system has the ability to identify and destroy cells infected with viruses or cells that are damaged or abnormal, such as cancer cells.
In the case of cancer, T-cells (part of the white blood cells) are the main fighters. For T-cells to get into action, a checkpoint protein, known as PD-1, on their surface must be activated. This protein is like a “regulator button” and helps keep the T-cells from attacking normal cells that have a PD-L1 protein on their surface. The reason for a T-cell to attack a normal cell with a PD-L1 is that some cancer cells have large amounts of PD-L1 protein.
To prevent normal cells from being attacked by T-cells, the checkpoint protein (PD-1) binds to PD-L1. Cancer cells that have PD-L1 seem to know and take advantage of this cover, thereby evading attacks from T-cells.
With this in mind, scientists developed new drugs called pembrolizumab, nivolumab and ipilimumab, which block this binding and boost the immune response against cancer cells. These drugs have been shown to be helpful in treating several cancer types, including that of the skin, lungs, kidneys, bladder, and head and neck.
Ipilimumab was approved by the Medicines Control Council for stage-four melanoma cancer two years ago. A woman in Johannesburg who had a stage-four melanoma was successfully treated with ipilimumab by Vorobiof as part of the phase-three clinical trial in 2005.
Vorobiof said: “Ten years later, the patient remains free of cancer.”
Since then, Vorobiof said, more drugs had entered the international market, though, in South Africa, only one (ipilimumab) is registered.
“The one [drug] that seems to be more active and durable is pembrolizumab. Clinical evidence from the 2015 Keynote 006 study shows that the long-term safety profile for pembrolizumab remains favourable, suggesting and confirming pembrolizumab as a standard of care for advanced melanoma,” he said.
Asked if immunotherapy is the future of skin cancer treatment, Vorobiof said: “Immunotherapy continues to grow in importance in the care of patients with melanoma.
“Combination strategies, including immunotherapy, are being evaluated. However, it’s too early to say that immunotherapy will be the ultimate cancer treatment because more research still needs to be done.”