Why do doctors not use chemo sensitivity testing before administering chemo?

Disappointing: There have been several attempts to demonstrate that these types of test can be helpful. Unfortunately, they have not been of great value. The hope is that the gene profile data might help us learn more about how to treat cancers. Also some of the studies might help us learn who will get side effects. Lung cancer mutation studies now show us who can benefit from targeted meds rather that chemo.

Controversial: Only been studied in non-small cell lung cancer. Mainly with a marker called ercc1. Ercc1 negative tumors showed a benefit with treatment. Those with high levels less benefit, however, it doesn't suggest that it won't work, it may just be less effective. So if we withhold therapy, then the patient may do worse. So at this time, the guidelines suggest not testing so use clinical judgement.