Women with a history of HER2-positive breast cancer show lower rates of relapse after inoculation.
A novel hybrid vaccine reduced recurrence rates in patients with HER2-positive breast cancer by 43% after 22 months in early results of a phase IIb randomized clinical trial. Of 201 patients rendered disease free by standard treatment, those who received the vaccination had a recurrence rate of about 10.3% compared to 18% in the control group.
“We need to continue to follow these patients, but there is enough of a trend that a phase III trial is warranted,” says Elizabeth Mittendorf, MD, a surgical oncologist at MD Anderson Cancer Center in Houston and the trial's national principal investigator. The results will be presented June 4 at the 2012 Annual Meeting of the American Society of Clinical Oncology.
Antigen Express of Worcester, MA, the company producing the vaccine and a partial funder of the trial, plans to follow up with a phase III study.
The vaccine teaches CD4+ T-helper cells, immune cells that are critical in mounting a response against foreign invaders, to recognize the HER2 protein, which is expressed at some level in 75% to 80% of breast cancer tumors. The vaccine's hybrid design combines a fragment of HER2 with a novel peptide based on the immune-regulatory li protein that, in laboratory tests, was found to enhance the potency of the vaccine 250-fold.
Because the vaccine is effective in tumors with any level of HER2 expression, it may aid patients who are not eligible for targeted therapy with Herceptin (trastuzumab; Genentech) because their tumor HER2 levels are too low.
If it is eventually approved, the vaccine could be delivered in any physician's office. The ongoing trial included monthly injections for 6 months followed by boosters every 6 months for 3 years. To heighten immune response, the vaccine was paired with an immune stimulant known as granulocyte macrophage colony-stimulating factor, which was also given to patients in the control arm of the trial.
The trial targets women who are disease free after standard-of-care treatment rather than those with metastatic disease, because the vaccine was not likely to overcome aggressive and invasive tumors. “It's a paradigm shift in trial design for cancer vaccines,” says Mittendorf, who is now developing a trial giving the vaccine with chemotherapy prior to surgery to test whether inoculation during immune system reconstitution improves outcomes.
©2012 American Association for Cancer Research.
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