Story at a glance
- Breast cancer is the second leading cause of cancer death in U.S. women, while Black women are more likely to die from the disease than white women.
- New findings from researchers at the University of Washington suggest a DNA vaccine could help treat an aggressive form of the disease.
- Researchers are currently recruiting participants for a phase II trial.
An experimental breast cancer vaccine has been shown to safely generate anti-tumor immunity in patients with advanced stages of the disease.
Data from the phase I trial indicate the vaccine could one day be used to treat different kinds of breast cancer.
The trial was conducted by researchers at the University of Washington School of Medicine and findings were published in JAMA Oncology.
“Because this was not a randomized clinical trial, the results should be considered preliminary, but the findings are promising enough that the vaccine will now be evaluated in a larger, randomized clinical trial,” said lead investigator Mary L. Disis, a professor of medicine at the University of Washington and director of the Cancer Vaccine Institute, in a statement.
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Around 42,000 women die of breast cancer each year in the United States, according to the CDC, while around 264,000 cases are diagnosed in women annually.
The vaccine was developed to specifically target the human epidermal growth factor receptor 2 (HER2) protein.
High levels of the HER2 protein — which helps cancer cells grow more quickly — are present in around 15 to 20 percent of breast tumors, while HER2 positive cases tend to be more aggressive and are more likely to recur after patients undergo treatment.
However, the overproduction of HER2 can also trigger cytotoxic — or cell-killing — immunity. Patients who have this type of immune reaction are less likely to have their cancer recur and tend to have longer overall survival than those without the reaction.
The DNA vaccine created by researchers stimulates this response in patients.
A total of 65 patients completed the trial which took place over the course of a decade; patients were followed up with for a median of 10 years. All patients received three injections of the DNA vaccine at varying doses (10 mcg, 100 mcg, or 500 mcg).
The strongest immune response was seen in patients who received the 100 mcg dose. Immunity persisted after the end of vaccinations and the vaccine was able to stimulate the response without triggering severe side effects, researchers said.
“The results showed that the vaccine was very safe,” Disis said. “In fact, the most common side effects that we saw in about half the patients were very similar to what you see with COVID vaccines: redness and swelling at the injection site and maybe some fever, chills and flu-like symptoms,” she added.
The trial was not designed to assess the vaccines’ efficacy in preventing or slowing breast cancer. However, the patients have done much better in the years following participation than what would be expected for those with similar disease stages, researchers said.
Under normal circumstances, around half would have died within five years of treatment. Eighty percent of participants are still alive after 10 years.
Some patients were receiving trastuzumab, a cancer drug, at the time of injection which may have influenced results.
The vaccine is currently being investigated in a randomized phase II trial and if results are positive “it will be a strong signal for us to rapidly move forward to a definitive phase III trial,” said Disis. Treatments that are successful in phase III trials are eligible for FDA approval.
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