A new genetic test has been successfully trialled at a hospital in Oxford to help doctors identify patients most at risk of chemotherapy side-effects. 

Capecitabine and fluorouracil (5FU) are common chemotherapy drugs for cancers including breast, bowl and stomach. Both drugs act as anti-metabolites and resemble biological molecules found inside cells. When the drug molecules are taken inside the cancer cell they disrupt normal metabolic processes causing cell death. Despite being effective chemotherapy drugs, both capecitabine and fluorouracil can cause harmful side-effects in patients.

A new genetic test aims to reduce the incidence of these potentially life-threatening side-effects, which can include heart problems and low blood cell counts. The DYPD gene has been linked to susceptibility to 5FU and capecitabine toxicity. Patients with variants in the DYPD gene were revealed to have increased susceptibility to both drugs and were therefore much more likely to develop side-effects after treatment.

Therefore, the chemotherapy dose can be adjusted depending on the patient’s genetic profile. Highly susceptible patients are given low doses to avoid side-effects, whilst patients with a high tolerance for the toxicity can be given a higher dose to try and increase the effectiveness of the chemotherapy.

Trials are now being undertaken to identify the cost effectiveness of the genetic test to see if it could be incorporated into NHS care in the future. The NHS is already prioritising personalised medicine, particularly in cancer treatment, with the new Genomic Medicine Service. The NHS hopes that this approach will increase the number of people surviving cancer each year through more effective use of existing therapies.