New drug added to chemo kills off residual breast cancer stem cells

New research says chemotherapy often fails to totally eliminate breast cancer because it does not knock out breast cancer stem cells.

The researchers working at Baylor College of Medicine (BCM) in Houston, Texas, say chemotherapy often leaves behind residual stem cells that help re-ignite cancer tumours and they compare the task to that of eradicating stubborn weeds from a garden.

Dr. Michael Lewis, assistant professor of molecular and cellular biology at the BCM Breast Cancer Center says it is not enough to kill the dandelion blossom and stalk that appear above ground, the root beneath the soil must be killed as well.

Dr. Lewis says their research has found that one reason chemotherapy frequently does not work is that while the bulk of the tumour is killed, many of the stem cells are left behind and their very nature makes them resistant to the effects of anti-cancer drugs.

Dr. Lewis says a cocktail of anti-cancer medicines together with the drug lapatinib appears to kill both the tumour and the stem cells and though the drug is still being evaluated, it could be used to treat breast cancer that has metastasized and contains the protein marker called HER2.

The researchers examined biopsies from tumours of patients with and without the HER2 marker before and after different treatments.

They found that the 31 patients whose tumors did not carry the HER2 marker, who received conventional chemotherapy, while the number of tumours significantly decreased, the proportion of cancer stem cells was greater than before the treatment.

In the other group, 21 patients with HER2 who were given lapatinib and two common breast cancer drugs, a dramatic drop was seen in tumour cells, and the percentage of cancer stem cells remained unchanged or even dropped slightly.

The researchers say in contrast to treatment with conventional chemotherapy, the relative proportion of stem cells did not go up, which means the stem cells were killed off with the same frequency as the bulk of the tumour; this is the first time this has been demonstrated.

The new drug shows promising results in reducing the stem cells conventional chemotherapy misses which gives added insurance that the breast cancer will not return.

The study which is published online in the Journal of the National Cancer Institute, was partly funded by GlaxoSmithKline, which makes lapatinib.