The remarkable recovery of a woman with advanced colon cancer, after treatment with cells from her own immune system, may lead to new options for thousands of other patients with colon or pancreatic cancer, researchers are reporting. Her treatment was the first to successfully target a common cancer mutation that scientists have tried to attack for decades. Until now, that mutation has been bulletproof, so resistant to every attempt at treatment that scientists have described it as “undruggable.”
An article about the case, from a team led by Dr Steven A Rosenberg, chief of surgery at the National Cancer Institute, was published in the December 2016 issue of The New England Journal of Medicine. The patient, Celine Ryan, 50, an engineer, database programmer and the mother of five, has an unusual genetic makeup that allowed the treatment to work. She is now cancer-free, though not considered cured. The treatment was a form of immunotherapy, which enlists a patient’s immune system to fight disease. The field is revolutionising cancer treatment.
Producing long remissions
An experiment on one patient cannot determine whether a treatment will be effective in others, but doctors said the results had the potential to help more people. “It has huge implications,” Dr Carl H June, from the University of Pennsylvania, USA, said in an interview. He was not part of the study, but wrote an editorial accompanying it in the journal. Carl said the research was the first successful targeting of a defect in a gene called KRAS, and is important because mutations in the gene are so common. “Every single pancreatic cancer patient has KRAS,” Carl said, adding that the pharmaceutical industry has spent billions trying unsuccessfully to target KRAS. Still, he said, the big question is whether this case is “one in a million, or something that can be replicated and built upon?”
About 53,000 cases of pancreatic cancer are expected in the United States this year, and nearly 42,000 deaths. It is one of the deadliest cancers; fewer than 10% of patients survive five years. Worldwide, it killed about 330,000 people in 2012, the most recent year with global statistics available. From 30 to 50% of colorectal cancers have KRAS mutations, too, and about 13% have the same mutation that Celine has. In the United States, about 95,000 cases of colon cancer and 39,000 cases of rectal cancer are expected in 2016, and 49,000 deaths from the two forms combined. Globally, there were 1.4 million cases and 694,000 deaths in 2012.
The new discovery might not have been made — at least, not now — without Celine’s persistence. Researchers twice denied her request to enter the clinical trial, saying her tumours were not large enough, she said. But she refused to give up and was finally let in. The research involves cancer-fighting immune cells called tumour-infiltrating lymphocytes, or TILs. These are white blood cells that swarm around tumours, a sign that the immune system is trying to attack the cancer.
Steven has been studying TILs for decades, with the goal of enhancing their ability to fight the disease and using them as a treatment. An attempt to treat another patient with tumours much like Celine’s did not work, almost certainly because the researchers could not produce enough highly targeted TILs, Steven said. So far, the cells have worked best against advanced melanoma, a deadly form of skin cancer. By extracting TILs from tumours, multiplying them in the lab and then returning them to the patient, Steven’s team has produced long remissions in 20 to 25% of patients with that disease.
More recently, the team has focused on an even tougher problem: tumours in the digestive system, including the colon and pancreas, and in ovaries, breasts and other organs. The researchers analyse tumours for mutations — genetic flaws that set the cancer cells apart from normal ones. They also study TILs, looking for immune cells that can recognise mutations and therefore attack cancerous cells but leave healthy ones alone.
Celine, from Rochester Hills, Michigan, had colon cancer that spread to her lungs despite surgery, chemotherapy and radiation. With few options, she began looking into research programmes and came across the TILs research at the National Cancer Institute, USA. In December 2014, she called the institute, hoping to join the study. But she was told, based on her scans and records, that she did not have a tumour big enough to yield TILs. A research nurse suggested she send her next set of scans; maybe, in the interim, the tumours would grow. Celine took that advice — and was devastated to be turned down again. “I felt sure I’d get in,” Celine said. “My heart sank.”
The rejection left her sobbing. But then she and her husband pulled up images of her scans on their home computer, took screen shots and measurements of a lung tumour that seemed to match the study criteria, and sent them to the cancer institute. She included a polite note asking that, if her tumour was not eligible, she be told why. “I was trying not to sound like a desperate maniac, but I was a desperate maniac,” she said. In March 2015, she got in. Whether the screen shots were a deciding factor is not clear. Steven said the team had been watching her progress and brought her in as soon as they identified operable tumours.
Medical gold mine
A month later, the researchers performed surgery, removing several lung tumours to search for TILs. Celine’s tissue turned out to be a medical gold mine. She had a KRAS mutation and her TILs included killer T-cells that locked onto the mutation like guided missiles. Her T-cells were able to recognise the mutation because she has an uncommon tissue type, which is a genetically determined trait. As a result, she carries a certain protein on the surface of her cells that plays an essential role in displaying the KRAS mutation so that cancer-killing cells can find it and attack.
Best of all, from a scientific standpoint, was that Celine’s KRAS mutation is shared by many other patients with colon and pancreatic cancers. Those who share her tissue type may also be good candidates for treatment with TILs. Researchers say they now have a blueprint that may enable them to develop cell treatments for other patients as well. The killer T-cells have surface molecules called receptors that lock onto mutated cells, and it may be possible to genetically engineer patients’ T-cells to give them those receptors and their cancer-targeting ability.