Breast Cancer Vaccine Showing Promise in Women With HER2 Overexpression

Recent findings from a phase II randomized clinical trial demonstrates that a breast cancer vaccine known as GP2, may help at preventing disease recurrence in women with HER2 protein overexpression. These results were presented by The University of Texas MD Anderson Cancer Center at the 2014 American Society of Clinical Oncology's Breast Cancer Symposium.

Women diagnosed with HER2-positive breast cancer with an overexpression score of +3 had no recurring disease when administered with the GP2 vaccine after completing trastuzumab (Herceptin) therapy. This safe and evidently effective vaccine is designed to stimulate CD8-positive T cells, along with an immune stimulant drug known as granulocyte macrophage colony stimulating factor (GM-CSF).

The clinical trial included 190 patients with various HER2 levels. Eighty-nine women received the GP2 vaccine plus GM-CSF, while the control group (91 patients) received GM-CSF alone. The disease-free survival (DFS) rate for those participating in the trial that received the vaccine was 88% compared to 81% in the control group-a 37% reduction. Furthermore, when excluding those eight patients that did not complete the vaccine series (early recurrence or experienced a secondary malignancy), the DFS was even higher-94% (vaccine) versus 85% (no vaccine)-reducing recurrence rates by 57%.

The subcutaneous injection is administered monthly for 6 months, followed by 4 cycles of booster shots every 6 months for those women with HER2 +3 disease having completed trastuzumab therapy.

For those women with HER2 +3 disease experiencing no disease recurrence, the administration of trastuzumab prior to GP2 therapy may be the reason why. The thought behind the success rate is that trastuzumab stimulates CD4-positve T cells to release substances that fight cancer cells by initiating an antibody response. Prepping the immune system prior to vaccine administration may be the one-two punch needed for minimizing disease recurrence.

“This is an important and different avenue in immunotherapy research, in that we are investigating ways to prevent cancer recurrence by stimulating the immune system to treat cancer,” says principal investigator Elizabeth Mittendorf, MD, PhD, associate professor of Surgical Oncology at the University of Texas MD Anderson Cancer Center. “The ultimate goal is to develop a preventative tool that will minimize the risk of recurrence in women who have already had breast cancer and for whom standard therapies have failed.”

MD Anderson is currently testing this combination of immunotherapy drugs in other clinical trials, leading to a more personalized approach in fighting various cancers.