Laura Dixon has a long history with cancer.

She was diagnosed with colon cancer in 1996, pancreatic cancer in 2013, and ovarian and endometrial cancer in 2014. Her treatment included several surgeries and a variety of chemotherapy drugs.

In 2015, a tumor in her liver turned out to be a pancreatic cancer recurrence.

But things were different this time.

The 49-year-old resident of Columbus, Ohio, had access to a clinical trial and a previously approved cancer drug called Keytruda. The clinical trial took place at The Ohio State University Comprehensive Cancer Center.

“I spoke with several doctors at several facilities,” Dixon told Healthline. “Everyone said it was my best shot. I think because they knew it was a genetic problem called Lynch syndrome, a genetic mutation that runs in the family. I didn’t hesitate. The side effects didn’t sound too terrible and I haven’t had many bad reactions, nothing to majorly change my life.”

But her life did change.

She received a 30-minute infusion of Keytruda every two or three weeks, for a total of 17 treatments.

A CT scan after 12 weeks showed the tumor had shrunk to half its original size. By the 20-week mark, it was down to a tiny “fleck.” Even that fleck was gone by the 45-week mark. She had her last infusion in April 2016.

“Now I go every three months for scans. I just had one and everything is still perfect,” Dixon said.

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What makes Keytruda a game changer

Keytruda, a type of immune therapy, was previously approved for treatment of specific cancers. These included metastatic melanoma, metastatic non-small cell lung cancer, recurrent or metastatic head and neck cancer, refractory classical Hodgkin’s lymphoma, and urothelial carcinoma.

When former president Jimmy Carter developed brain tumors due to metastatic melanoma, Keytruda got the credit for shrinking them.

Now there’s a new use for the drug.

In May 2017, the U.S. Food and Drug Administration (FDA) approved Keytruda to treat any solid tumor with a specific genetic feature rather than the location of the original tumor. It was a first.

The new approval is for treatment of unresectable or metastatic solid tumors that have a specific biomarker called microsatellite instability-high (MSI-H) or mismatch repair deficient (dMMR).

Dixon’s tumor had the biomarker.

This type of tumor is most likely to be found in colorectal, endometrial, and gastrointestinal cancer. About 5 percent of people with metastatic colorectal cancer have one of these biomarkers.

It can also be found in other cancers, including breast, prostate, bladder, and thyroid.

It’s intended for people who are experiencing disease progression even after receiving first-line therapies.

The drug was studied in five uncontrolled, single-arm clinical trials. Of the 149 patients who received Keytruda in the trials, 39.6 percent had a complete or partial response. For 78 percent of those patients, the response lasted for six months or more. Further studies are underway.

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How Keytruda may impact future treatment

Dr. John Hays is a cancer specialist at The Ohio State University Comprehensive Cancer Center where Dixon received treatment.

He told Healthline the new approval for Keytruda is an important precedent going forward — that this kind of therapy can be used for certain types of cancer independent of origin.

He cautioned that this is not a first-line treatment, at least not yet.

“If you take colon cancer and patients that have MSI-H tumors, the upfront therapy is chemotherapy. The standard of care isn’t to give immune therapy.”

For now, the new use of Keytruda is intended for people who have progressed despite other types of treatment.

How many people might benefit? Hays said it’s hard to give exact numbers.

“While it may help only a few patients with one type of cancer, it may help thousands with other types of cancer. We’ve spent many years treating cancer based on origin. We’ve come a long way and we don’t want to throw all that info out, but this is a big step in a different direction,” Hays said.

“People think this is the way going forward, but we shouldn’t stop what we’ve learned about specific cancers in the past. Immune therapy was in its infancy 10 to 15 years ago and has really come full force in the last five years. In some cases, it’s spectacular, as in MSI-H tumors and Lynch tumors. But in some cases, it doesn’t work that well. It’s not the Holy Grail.”

Hays explained that Keytruda may cause side effects.

“I wish I had a drug with great efficacy and zero side effects. What we tend to see with Keytruda is that most people have mild side effects and it’s generally better tolerated than chemo. But some patients have very severe, even life-threatening side effects.”

It’s also expensive, costing about $12,500 per month.

Hays said that most insurers are covering it for approved cancers. He suspects the new approval will likely be covered as well.

The regulatory path forward

This new use for Keytruda was possible because of the FDA’s Accelerated Approval regulations. The FDA can speed up the approval process when there’s an unmet need for a serious condition.

Instead of waiting to determine if a drug extends survival time, it can be approved based on evidence that it shrinks tumors. Further trials are required to confirm. In the meantime, Accelerated Approval can get new treatment to patients whose options are limited.

Dr. Gwen Nichols, chief medical officer of the Leukemia & Lymphoma Society (LLS), told Healthline she’s encouraged by this approval.

“This approval, based primarily on patients with colon cancer, was exciting,” she said. “Not because of large patient numbers, but the idea that regulators have opened their minds and are supportive of this. Prior to this, we often didn’t see a path forward to get certain drugs approved. This is really a radical change. The fact that the FDA is looking at how to do this is a whole new world for agents drug companies would have thrown out otherwise.”

So, is this type of approval the future of cancer treatment? Nichols believes it is.

“If we can find out how tumor biology directs tumor cells to become cancerous, we can focus on that biology instead of having general treatments for breast cancer or colon cancer.”

Nichols said there are obstacles to bringing a new drug to market.

“What’s tricky from a drug development point of view is that companies developing drugs are always looking for a percentage of all colon cancer patients, for example, to respond to a drug. So we’ve lost some interesting potential drugs because they only worked in a small percentage of patients.”

Drug companies can’t show a survival benefit if they treat many patients, but only a small percentage respond.

“If we can use biomarkers to help us say this is the group of patients where this will work and improve survival rates, and these are the patients who don’t need treatment with this agent, we can be much more focused about the population we test and treat,” explained Nichols.

Other similar treatments are currently in the works.

The LLS has a precision medicine research program called Beat AML.

“We’re testing the genetics of AML patients during the initial presentation of disease,” explained Nichols.

“Then we’re giving them a drug, or combination of drugs, that address the mutation we find in leukemia cells. We want to see if we can be more precise in treatment based on what we find in a biomarker test, rather than treating all patients with AML the same way. This type of precision medicine is the wave of the future.”

Dixon is grateful for the clinical trial and for Keytruda.

She advises others who have a tough diagnosis to explore clinical trials and ask a lot of questions.

“The research being done is revolutionary. They’re finding new things every day for genetic problems rather than the kind of cancer you have. Don’t give up because of a bad diagnosis,” said Dixon.