Researchers Find Way to Identify When Tamoxifen Likely to Fail

Researchers at Cancer Research UK have discovered a key chemical switch that explain why some breast tumors are resistant to tamoxifen.

Although tamoxifen has been shown to be effective as a treatment for breast cancer, the drug does not work on all tumors.

These findings, published in the journal Oncogene, are being used to develop a new testing procedure to find which cancers have the switch activated. The identification of the switch is an important step to finding ways of predicting which tumors will respond to the drug.

"It's important that we learn to identify women who are not going to respond to the drug, so we can spare them from unsuccessful treatment and explore other ways of looking after them," said Dr. Simak Ali, lead author of the study.

Researchers looked at estrogen receptors in breast tumors to see if they differed from the normal form of the molecule. They discovered that part of the molecule becomes altered chemically and the altered form of the estrogen receptor seems to become more active in response to tamoxifen rather than being inactivated.

"Chemical alteration seems to switch the estrogen receptor molecule into a completely different state, in which it becomes immune to the inhibitory effects of tamoxifen," said Ali.

Ali and his team have developed antibodies that can detect the altered form of the estrogen receptor molecule. They are in the process of developing a method of testing for the altered molecule in tumor biopsy samples so that women can be given the correct form of treatment.

"At the moment, we have only a relatively primitive system for monitoring tamoxifen treatment," said Ali. "We're aiming to develop a much more sophisticated testing procedure, potentially saving valuable time that might otherwise be wasted on unsuitable treatments."

Other sources: Oncogene