The US Evaluation of Genomic Applications in Practice and Prevention (EGAPP) Working Group (EWG) has released evidence-based recommendations on the validity and utility of three genetic tests currently being used in clinical practice. The new recommendations were made regarding three tumour genetic profiling tests used in breast cancer patients; the use of UGTIA1 gene testing in people affected with metastatic colorectal cancer treated with irinotecan; and on genetic testing strategies to identify Lynch Syndrome in newly diagnosed colorectal cancer cases.
EGAPP published their recommendations in the January 2009 issue of Genetics in Medicine, with details on the methods used for collecting and analysing their data, in the hope that it may be helpful to 'other groups conducting evidence-based reviews of genomic applications'.
Lynch Syndrome is an inherited genetic condition that causes colorectal cancer (CRC), otherwise known as cancer of the bowel. Discovering whether newly diagnosed bowel cancer patients have the inherited form of the disease might aid in early identification and treatment of the cancer in their relatives.
Metastatic colorectal cancer is a cancer that has spread from the bowel to other areas of the body, and one treatment is irinotecan, a chemotherapy agent whose side-effects include extreme suppression of the immune system. People with a specific variant in the UGT1A1 gene do not produce as many of the enzymes the body uses to break down irinotecan, and so during chemotherapy they effectively receive a larger dose as the body cannot clear the agent quick enough.
Measuring the activity of different genes in breast tumour tissue is proposed as a way to estimate the risk of disease recurrence in breast cancer patients and to provide additional information to inform treatment decisions.
EWG concluded that there was sufficient evidence on the clinical utility and analytical and clinical validity of genetic testing for Lynch Syndrome and recommended that those diagnosed with CRC be offered the test. However, they concluded that there was inadequate evidence for or against the clinical utility of the remaining two tests, meaning no firm recommendations on these tests could be made. In particular EWG found no direct evidence linking tumour gene activity profiling of breast cancer patients to improved outcomes, and in the case of UGT1A1 gene testing they found 'contextual issues' that demonstrated both the benefits and harms of testing.