Guardant Health announces initial results from Pegasus trial

Guardant Health announced that initial results from the Pegasus trial suggest liquid biopsy may be used in post-surgical clinical management to reduce unnecessary toxicity from chemotherapy and improve the response to standard chemotherapy regimens in patients with stage III or high-risk stage II colon cancer. Results from the trial, which is an ISS study sponsored by IFOM ETS – the AIRC Institute of Molecular Oncology in Milan, Italy, and supported by Guardant Health, were presented today by study investigators at the ESMO Congress in Madrid, Spain. One of the first prospective studies using liquid biopsy, the Pegasus trial includes 135 patients recruited from 11 cancer centers in Italy and Spain. The study is assessing the feasibility of escalating or de-escalating adjuvant chemotherapy based on the presence or absence of minimal residual disease, or MRD, as indicated by circulating tumor DNA, or ctDNA, detected by the Guardant Reveal blood test at multiple timepoints. Patients with positive results receive standard chemotherapy, while patients with negative results receive a milder therapy that is associated with significantly less acute and chronic neurological toxicity compared to standard treatment. Liquid biopsy is repeated several times along the course of treatment to reveal opportunities to treat patients safely with lower toxicity regimens, identify therapeutic resistance, and tailor chemotherapy to be stronger when needed. Initial results show that 34% of patients with a liquid biopsy result after surgery had the cancer return, while only 10% of patients with a negative result experienced a relapse. Approximately 40% of patients converted from ctDNA-positive to ctDNA-negative after treatment, suggesting treatment efficacy of chemotherapy for some patients.