In Largest Molecular Residual Disease (MRD) Study in Colon Cancer, Guardant Reveal Testing Prior to Chemotherapy Provides Robust Stratification for Risk of Disease Recurrence and Survival to Enable Timely Treatment Decisions

• Data support routine use of circulating tumor DNA testing in management of stage III colon cancer patients
• Tumor fraction analysis provides further insights for patient management in patients with ctDNA detected

Guardant Health, Inc. (Nasdaq: GH), a leading precision oncology company, and its research collaborators today presented results of the largest study to date evaluating circulating tumor DNA (ctDNA) in colon cancer prior to chemotherapy, demonstrating the ability of the Guardant Reveal™ test to stratify the risk of disease recurrence and overall survival, and thus inform treatment decisions after surgery. Data from the phase III trial of FOLFOX-based adjuvant chemotherapy (NCCTG N0147) involving over 2,000 patients with stage III colon cancer with median follow-up of 6.1 years were presented at the 2025 American Society for Clinical Oncology (ASCO) Annual Meeting.

Results demonstrated that circulating tumor DNA detected in the bloodstream after cancer surgery and prior to the start of adjuvant therapy, using the Guardant Reveal test, is a strong predictor of the risk of disease recurrence and poorer survival, and suggest the potential for ctDNA testing to improve decision-making at a critical time point for post-operative chemotherapy. Specifically:

• Among patients with post-surgical ctDNA detected, 62.6% had the cancer return within 3 years, despite having had adjuvant chemotherapy, while only 15.4% of patients with undetectable ctDNA recurred in the same period.
• The level of ctDNA, or tumor fraction, showed promise in identifying individuals who are less likely to clear residual disease with adjuvant treatment.

“Thirty percent of patients with stage III colon cancer will relapse after surgery, despite having standard adjuvant chemotherapy,” said Frank Sinicrope, MD, professor of oncology and medicine at Mayo Clinic and principal investigator for the study. “In this study, we demonstrate that analysis of postsurgical ctDNA can improve the prediction of disease recurrence over standard staging criteria, which may help guide patient management and follow-up. These data further support the routine use of ctDNA in management of stage III colon cancer patients.”

“With the Guardant Reveal test, a simple blood draw can be used to identify colorectal cancer patients who have molecular residual disease and are most likely to benefit from adjuvant therapy,” said Helmy Eltoukhy, Guardant Health chairman and co-CEO. “This large study confirms the test’s ability to identify high risk of cancer returning and support oncologists in making more informed therapeutic decisions to help improve patient outcomes.”

The full abstract for the presentation can be found on the ASCO website.

About Guardant Reveal

Guardant Reveal, which runs on the Guardant Infinity™ smart liquid biopsy platform, is a blood test that uses epigenomic (methylation) analysis to detect circulating tumor DNA, a marker of minimal residual disease, to predict cancer recurrence, helping to guide clinical decisions after surgery or chemotherapy. The test is covered by Medicare for patients with colorectal cancer in the early post-surgical setting and for surveillance testing to monitor for disease recurrence after curative intent treatment.

About Molecular Residual Disease

Molecular residual disease refers to a subclinical measure of cancer burden that remains during and following treatment. A patient’s MRD status is a reliable indicator of clinical outcome and response to therapy and can be used for risk stratification and to guide treatment options when used in conjunction with other clinical data.

About Guardant Health

Guardant Health is a leading precision oncology company focused on guarding wellness and giving every person more time free from cancer. Founded in 2012, Guardant is transforming patient care and accelerating new cancer therapies by providing critical insights into what drives disease through its advanced blood and tissue tests, real-world data and AI analytics. Guardant tests help improve outcomes across all stages of care, including screening to find cancer early, monitoring for recurrence in early-stage cancer, and treatment selection for patients with advanced cancer. For more information, visit guardanthealth.com and follow the company on LinkedIn, X (Twitter) and Facebook.

Forward-Looking Statements

This press release contains forward-looking statements within the meaning of federal securities laws, including statements regarding the potential utilities, values, benefits and advantages of Guardant Health’s liquid biopsy tests or assays, which involve risks and uncertainties that could cause the actual results to differ materially from the anticipated results and expectations expressed in these forward-looking statements. These statements are based on current expectations, forecasts and assumptions, and actual outcomes and results could differ materially from these statements due to a number of factors. These and additional risks and uncertainties that could affect Guardant Health’s financial and operating results and cause actual results to differ materially from those indicated by the forward-looking statements made in this press release include those discussed under the captions “Risk Factors” and “Management’s Discussion and Analysis of Financial Condition and Results of Operation” and elsewhere in its Annual Report on Form 10-K for the year ended December 31, 2024, and in its other reports filed with or furnished to the Securities and Exchange Commission thereafter. The forward-looking statements in this press release are based on information available to Guardant Health as of the date hereof, and Guardant Health disclaims any obligation to update any forward-looking statements provided to reflect any change in its expectations or any change in events, conditions, or circumstances on which any such statement is based, except as required by law. These forward-looking statements should not be relied upon as representing Guardant Health’s views as of any date subsequent to the date of this press release.

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