A new experimental vaccine is safe and effective in stimulating the immune system to regress early-stage breast cancer, according to the results of a latest human trial. Deregulation and inhibition of the immune system contributes to cancer development. Many therapeutic strategies aim to re-stimulate the immune system to recognise cancer cells and target them for destruction.
Researchers from Moffitt Cancer Centre in the US report that a dendritic cell vaccine that targets the HER2 protein on breast cancer cells is safe and effectively stimulates the immune system leading to regression of early-stage breast cancer.
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The HER2 protein is over-expressed in 20-25 per cent of all breast cancer tumours and is associated with aggressive disease and poor prognosis.
The strategies that can re-stimulate the immune system to recognise and target HER2 early during cancer development may be effective treatment options, researchers said.
The approach involves creating the vaccine from immune cells called dendritic cells that are harvested from each individual patient to create a personalised vaccine.
To determine if the HER2-dendritic cell vaccine is safe and effective, the researchers performed a clinical trial in 54 women who have HER2-expressing early-stage breast cancer.
The dendritic cell vaccines were prepared by isolating dendritic cells from each patients’ blood and exposing them to fragments of the HER2 protein.
Patients were injected with a dose of their personal dendritic cell vaccine once a week for six weeks into either a lymph node, the breast tumour, or into both sites.
The researchers report that the dendritic cell vaccines were well-tolerated and patients only experienced low-grade toxicities.
The most common adverse events were fatigue, injection site reactions, and chills. They also show that the vaccine was able to stimulate an immune response in the majority of the patients.
About 80 per cent of evaluable patients had a detectable immune response in their peripheral blood and/or in their sentinel lymph node wherein their cancer is most likely to spread to first.
Importantly, the immune responses among the patients were similar, regardless of the route of vaccine administration.
The researchers assessed the effectiveness of the vaccine by determining the percentage of patients who had detectable disease within surgical specimens after resection.
The absence of disease is termed a pathological complete response (pCR).
They report that 13 patients achieved a pCR and patients who had early non-invasive disease called ductal carcinoma in situ (DCIS) achieved a higher rate of pCR than patients who had early-stage invasive disease.
Interestingly, patients who achieved a pCR had a higher immune response within their local sentinel lymph nodes.