Your body's first-line defense against foreign invaders is your own immune system.
When it sees an invader, it unleashes T cells to destroy it.
Some forms of cancer can trick the immune system into seeing cancer cells as healthy cells. Hiding in plain sight, they are free to grow and reproduce.
That's where immunotherapy comes in.
Immunotherapy is a way to stimulate the immune system to attack cancer cells. It's already being used to treat some forms of cancer, and more in the future.
"Immunotherapy for cancer treatment is exploding," said Dr. David Chan, program director for oncology at Torrance Memorial Medical Center in California. "It's the current big thing in cancer research."
He also noted it's one of the reasons for rising healthcare costs, particularly in cancer treatment.
While immunotherapy is nothing short of a miracle for some cancer patients, it doesn't work for everyone.
And whether it works or not, it's also impacting healthcare costs.
The potential of immunotherapy
We're only beginning to scratch the surface of the potential of immunotherapy to treat cancer.
In an interview with Healthline, Chan said most of the recent interest in immunotherapy has to do with a class of drugs known as immune checkpoint inhibitors.
He explained that cancer sometimes fools T cells with a protein that works like a mask. The protein, called PD-L1, blocks T cells from recognizing cancer cells. Rather than attack, the T cells allow cancerous cells to grow.
Chan said cancer researchers have been trying to harness the immune system for 30 years.
"About a decade ago, they started developing antibodies to treat HER2-positive breast cancer," he said. "It's a very aggressive form of breast cancer. It had higher recurrence and fatality rates than other breast cancers. It was very difficult to treat prior to immunotherapy."
Until a drug called Herceptin came along.
Herceptin binds to HER2 receptors and blocks them from growth signals. At the same time, it stimulates the immune system to destroy cancer cells.
Chan said Herceptin has dramatically improved the cure rate for HER2-positive breast cancer.
Some of his patients have been in remission for 10 years or more.
"When that pathway is interrupted, it unmasks the cancer so T cells recognize it and activate. The result is a significant reduction in cancer and prolonged survival," he said.
He noted there are currently four FDA-approved drugs that work through this kind of pathway.
Malignant melanoma, non-small cell lung cancer (NSCLC), kidney, bladder, and head and neck cancers can all be treated with immune checkpoint inhibitors.
According to Chan, one quarter to one third of patients treated with immune checkpoint inhibitors show signs of regression or remission.
He added that, for the most part, immunotherapy is fairly well-tolerated and can continue indefinitely. Unlike chemotherapy and radiation, immunotherapy leaves healthy cells unscathed.
However, sometimes the immune system overreacts to the therapy. That means treatment must be stopped while side effects are addressed. Chan said during that time, the cancer often remains in check.
A severe immune system overreaction is potentially fatal.
Not all patients respond to immunotherapy.
"It's not a cure-all. When it works, it works really well. But the majority of patients won't respond to checkpoint inhibitors," said Chan. "If we use immunotherapy for a typical approved cancer, one of three patients will benefit."
Currently, there's no way to know in advance which category patients will fall into.
"Not every antibody is the same, not every cancer is the same. The difficult part is trying to identify, molecularly, which patients will benefit. Through research, we'll have to figure it out cancer by cancer and drug by drug," said Chan.
Combining immunotherapies with other cancer treatments may offer promise, but Chan explained that it's a complicated issue.
"It's not going to be a simple thing where there's a single way to treat cancer. But without question, it will improve cure rates and quality of life," he said.
Dr. Mark Faries, director of the Donald L. Morton, M.D., Melanoma Research Program, and director of therapeutic immunology at the John Wayne Cancer Institute at Providence Saint John's Health Center in California, agrees.
He told Healthline it's still too soon to say how safe and effective combination therapy will be.
"We know that some combinations of immunotherapies are better than one immunotherapy by itself," he said. "There are clinical trials to evaluate combining these medications with other types of treatments including chemotherapy, targeted therapies, and radiation. We have also had good experiences with patients who have had immunotherapy and surgery. But the complete answer to this question will come through multiple clinical trials over the next several years."
The problem of cost
Immunotherapy is expensive.
"We're talking about treatments that cost over $100,000 per year," said Chan. "Combine drugs and it's over $200,000 per year."
Chan believes when we identify who will benefit and who won't, it will make a big difference in cost for patients and in overall healthcare costs.
Immunotherapy is often covered by health insurance, but patients still have to deal with rising out-of-pocket costs. Surgery and other cancer treatments add still more to the financial burden.
According to Chan, cost is a big problem.
"We've got to try to make these treatments available at a lower cost. The United States pays far higher costs for drugs than other countries. We're the only ones who don't take cost into account before approving a drug. We don't negotiate costs with drug companies. Americans are bearing the price of drug research for the entire world," he said.
Faries also looks at the potential long-term benefits.
"If the therapy is curative, the total cost of therapy might be less than would be the case for repeated courses of less expensive, but less effective treatments such as chemotherapy," he explained.
"One of the main potential advantages of immune therapy relative to other cancer medical treatments is the durability of the responses. Some patients who have good responses seem to maintain them for many years, possibly forever. While there can be side effects to the treatments, even severe or life-threatening side effects, quality of life is frequently quite good and side effects are generally able to be controlled," said Faries.
"A long-term, durable remission might allow patients to return to work and productivity. But given the price of these drugs, cost effectiveness analysis will be an important component of future research," said Faries.
By Ann Pietrangelo