by Lisa Jarvis
Imagine a future where far fewer women are diagnosed with breast cancer, and women with a family history of breast cancer don’t have to make the difficult, even devastating choice to get a preventive mastectomy. Instead, women would get a series of shots that teach their immune systems how to quash breast cancer before it becomes a problem.
A decade or two ago, that future would have sounded fantastical. But in the last six months, multiple clinical trials have brought that much closer to reality. These studies are very early — so far only a handful of people have even gotten the shots.
Yet the arrival of not just one but several breast cancer vaccine studies is an encouraging sign of the amazing progress researchers are making in harnessing the immune system to not just battle cancer, but prevent it in the first place. The potential for treating breast cancer — the most common form of cancer among U.S. women — is huge.
“We are literally vaccinating healthy people now,” says Susan Domchek, an oncologist at the University of Pennsylvania who is leading a trial of a preventive breast cancer vaccine. “It’s not just pie in the sky, we’re actually doing it.”
She is one of several researchers making serious headway toward that ambitious goal. Decades of work to understand how to train the immune system to spot tumors has culminated in a cluster of clinical studies of breast cancer vaccines that aim to be truly preventive.
Eventually, “there will be vaccines available for every different type of breast cancer,” says Nora Disis, director of the University of Washington’s Cancer Vaccine Institute. Disis, an expert in breast cancer immunology, believes chances are high that vaccines to treat or prevent recurrence of the disease will arrive within the next five years. And eventually, vaccines could be available to keep women with a genetic risk of developing cancer from ever having to deal with it.
One early sign of the vaccines’ promise came last November, when Disis’s team published results from a years-long study of a vaccine that teaches the immune system to spot a mutated form of the protein HER2, a common driver of breast cancer. Researchers vaccinated 66 women who were either in remission following treatment for their breast cancer or had slow-growing tumors.
The study was designed to prove the shots were safe, but it also yielded a hopeful signal the approach is working: Women in the study had a 50% chance of dying from the disease within five years of treatment, but after a decade, 80% are still alive. The researchers are now starting a larger study.
That’s one of several breast cancer vaccines that Disis is developing, with the idea that showing they work to keep cancer from coming back is just the first step in moving them into earlier stages of disease — and eventually prevention.
Others are already moving into studies of vaccines that could prevent disease in people with a high risk of developing breast cancer. In general, those trials are vaccinating women about to undergo preventive mastectomies so that they can look for an immune response in tissue removed during surgery. Then, of course, they will need to follow those women for years to understand if that immune response is enough to keep cancer at bay.
In March, Domcheck vaccinated the first three healthy women who harbor BRCA mutations that put them at high risk of developing cancer. Before their mastectomy, the volunteers were given a shot that teaches the immune system to see an enzyme called telomerase, which is turned up too high in cancer cells.
And in February, researchers at the Cleveland Clinic similarly began vaccinating women who do not have breast cancer but carry mutations like BRCA or PALB2. The shot they get before surgery teaches their immune system to recognize a protein that normally is only made when women are lactating, but seems to reappear in triple-negative breast cancers — one of the most aggressive forms of the disease. If it works, their vaccine could be safe for women who are past their child-bearing years.
Proving these vaccines can prevent cancers eventually will require large, late-stage studies — the kind academic centers can’t typically afford. “It’s going to take advocates, patients, and funding to get this type of work done,” Domchek says.
As these studies wind through the clinic, any promising data should motivate investment in an area that could bring us close to the vision of a world with a lot less cancer in it.
Patients are doing their part. Lee Wilke, an oncologist at University of Wisconsin’s UW Health who is leading a phase 2 study one of Disis’ vaccines, says she has a long list of people who’d like to roll up their sleeve for the trial.
Wilke routinely performs mastectomies and is more than ready for the day when vaccines allow women to make different choices about their health. Maybe a vaccine can allow women with a high risk of developing breast cancer to delay surgery until after they’ve had children. Maybe it’ll eventually mean forgoing surgery altogether and living cancer-free. “I keep telling my colleagues in research and pharmacology: Please, put me out of business,” she says.
And while I normally wouldn’t wish for anyone’s unemployment, to me that sounds like a pretty good goal.
