Rare Genetic Mutations May Increase Severe Taxotere Side Effects

Some people treated with the chemotherapy drug Taxotere (chemical name: docetaxel) experience severe, life-threatening side effects. New research suggests rare gene mutations may be to blame.  

People with certain gene mutations may have problems breaking down some breast cancer drugs, like fluorouracil or tamoxifen. As a result, these drugs can build up in the body, leading to severe side effects. Taxotere side effects like low white blood cell count, fever, and infections may be linked to this buildup of medicine.   

Taxotere is broken down by an enzyme called CYP34A. This enzyme is made by the gene CYP3A. But mutations in the gene can stop the enzyme from properly working. The researchers wanted to know if CYP3A4 mutations could be leading to Taxotere’s severe side effects.

The researchers studied 3,208 people who had previously been treated with Taxotere, eight of whom had CYP3A4 gene mutations. Six of the eight people with the mutations (75%) experienced severe side effects,  including low white blood cell count (neutropenia) and fever associated with neutropenia — both of which can be life-threatening. In comparison, only 56% of the other participants experienced these side effects. 

If Taxotere is part of your treatment and you’re worried about severe side effects, you may want to talk to your doctor about testing for CYP3A4 mutations. If a mutation is present, your doctor may prescribe you Taxol (chemical name: paclitaxel) instead.