A study found that breast cancer cells that had high levels of the PARP (polyadenosine diphosphate ADP-ribose polymerase) enzyme were more likely to respond to chemotherapy. These results were presented at the 2010 European Breast Cancer Symposium.
DNA carries genetic information in both healthy and cancer cells. Chemotherapy medicines work against cancer by damaging the DNA or blocking DNA reproduction. But all cells can fix DNA damage caused by chemotherapy medicines; the PARP enzyme helps fix this DNA damage. So while it seems likely that chemotherapy wouldn't be effective on breast cancers with the highest PARP levels, this study found that wasn't true. Breast cancers with the highest PARP levels responded the best to chemotherapy.
The researchers measured PARP levels in cells from breast cancer tissue samples. The samples were put into three groups based on PARP levels: low, medium, and high. About 66% of the tissue samples had medium or high PARP levels.
The researchers looked at how well each cancer responded to chemotherapy. The response was measured as pathologic complete response, which means a biopsy showed no signs of cancer after chemotherapy.
Pathologic complete response was found in:
- 8% of cancers with low PARP levels
- 19.1% of cancers with medium PARP levels
- 26.5% of cancers with high PARP levels
So it seems that PARP levels might help predict if a breast cancer is likely to respond well to chemotherapy.
More research is needed to better understand if and how to use PARP levels to predict how breast cancer will respond to chemotherapy.
Stay tuned to Breastcancer.org for the latest news on emerging breast cancer treatments.