A promising new cancer "vaccine" that cured up to 97 percent of tumors in mice will soon be tested in humans for the first time — but experts say that we're still a long way off from this type of drug being prescribed to cancer patients.

Researchers from Stanford University will test the therapy in about 35 people with lymphoma by the end of the year, according to SFGate, a local news outlet in San Francisco. The treatment stimulates the body's immune system to attack cancer cells. In studies in mice with various cancers — including lymphoma, breast cancer and colon cancer — the treatment eliminated cancer tumors in 87 out of 90 mice, even when the tumors had spread to other parts of the body, the researchers said.

Dr. Alice Police, the regional director of breast surgery at Northwell Health Cancer Institute in Westchester, New York, who was not involved in the study, said that the news of a human trial to test this treatment is "exciting." However, she cautioned that results in animal studies don't always translate to people.

"We've been able to cure a lot of cancers in mice for a long time," Police told Live Science. What's more, the current human trials are for patients with lymphoma, and so it could be many years before doctors know if this treatment works for other cancers, such as breast and colon cancer, Police said. [10 Do's and Don'ts to Reduce Your Risk of Cancer]

A cancer vaccine?

The new treatment is not technically a vaccine, a term used for substances that provide long-lasting immunity against disease. But the treatment does involve a vaccine-like injection, SFGate reported. (According to the American Society of Clinical Oncology, a "cancer vaccine" can refer to a treatment that's used to prevent cancer from coming back and destroys cancer cells that are still in the body.)

Instead, the treatment is a type of immunotherapy. It contains a combination of two agents that stimulate T cells, a type of immune cell, to attack cancer. Normally, the body's T cells recognize cancer cells as abnormal and will infiltrate and attack them. But as a tumor grows, it suppresses the activity of the T cells so that these cells can no longer keep the cancer at bay.

The new treatment works by reactivating these T cells. Researchers inject the "vaccine" directly into the tumor. The two agents in the treatment work synergistically in activating the T cells. Because these T cells were already inside the tumors, they have essentially been "prescreened" by the body to recognize cancer-specific proteins, the researchers said.

In the animal studies, injecting the treatment into just one tumor worked to eliminate tumors in other parts of the body (so-called metastatic cancers). This occurs because active T cells migrate to other parts of the body and destroy tumors that have spread.

In a study that was published Jan. 31 in the journal Science Translational Medicine, scientists gave the treatment to mice that were genetically engineered to develop breast cancer in all 10 of their mammary pads. The drug was injected into the first tumor that appeared in the animal, and the researchers found that the treatment also prevented the occurrence of future tumors in many cases, the researchers said.

Promising immunotherapies

Immunotherapy is not new; indeed, several other immunotherapies have been approved for treating cancer. For example, a treatment called CAR T-cell therapy, which was recently approved for some types of leukemia and lymphoma, involves removing certain immune cells from patients' bodies and genetically engineering those cells to fight cancer.

Compared with CAR T-cell therapy, one advantage of the new treatment is that it doesn't require doctors to remove and customize the patient's immune cells for fighting cancer, the researchers said. "We're attacking specific targets without having to identify exactly what proteins the T cells are recognizing," Dr. Ronald Levy, a professor of oncology at Stanford University School of Medicine and the senior author of the Science Translational Medicine study, said in a statement.

It's also interesting that the work may have implications for colon and breast cancer, two cancers for which there are currently no immunotherapies, Police said.

"We've [gone] one step further down the road" to an immunotherapy for these cancers, Police said. "But it's [still] a long way to go."

The new trial is a phase I study, which means it will test only the safety of the treatment and is not designed determine how effective it is.

Original article on Live Science.