Understanding individual genetic variation can help predict chemotherapy side effects

The largest study ever on the effect of genetic variability on the toxicity of chemotherapy in breast cancer shows that it is possible to predict which patients are most likely to suffer serious side effects, a researcher will tell the 8th European Breast Cancer Conference (EBCC-8) today (Friday). Dr. Christof Vulsteke, from the Catholic University of Leuven, Belgium, will explain how his team's research is an important step towards achieving a personalised chemotherapy regime for each patient.

The researchers examined germline DNA[1] from blood samples from 1089 breast cancer patients who were treated between 2000 and 2010 with three commonly used chemotherapy drugs (fluorouracil, epirubicin and cyclophosphamide). For each patient, the variability in the genes that are important for metabolising these three chemotherapeutic drugs was compared with the side effects experienced.

"We found that genetic variation in one gene was highly correlated with chemotherapy side effects," says Dr. Vulsteke. "Investigating this gene before starting chemotherapy would allow us to support the patient with either growth factors to increase the patient's immunity, or dose modifications, or a different chemotherapy regimen better adapted to the patient, or a combination of these."

Currently, most patients receive the standard treatment; however, the side effects they suffer can be very different, ranging from severe to very minimal reactions. Making adjustments to treatment would have a major impact on both the physical and psychological well-being of patients, and on the financial burden to society posed by chemotherapy side effects, for example, hospitalisation.

The most important side effects of chemotherapy are mainly caused by immune system depression, which can result in potentially life threatening infections. Even though patients may take every precaution to avoid contamination, the vast majority of these infections are caused by naturally occurring microorganisms in the patient's own gastrointestinal tract. Other serious side effects noted in patients receiving chemotherapy are bleeding, severe infection of the mouth mucosa, severe bowel inflammation, nausea, and vomiting with dehydration.

Scientists have made a great deal of progress in developing therapies to help manage the side effects of chemotherapy. Newer cancer treatments and supportive care treatments have led to vast improvements in the management of symptoms associated with cancer treatment. Although chemotherapy is designed to treat cancer cells, unfortunately, it often affects parts of your body not directly affected by the cancer itself. This undesired result is referred to as a complication of treatment, or a side effect. Some people don't experience side effects at all, and you are unlikely to experience all the side effects you read about below. There is no way to tell who will experience side effects or which side effects they may experience.

Side effects may be acute (short-term), chronic (long-term), or permanent. Side effects may cause inconvenience, discomfort, serious illness and even death. Additionally, certain side effects may prevent doctors from delivering the prescribed dose of chemotherapy at the specific time and schedule of the treatment plan.