Ultrasensitive Assay Tracks Resistance Mutations MRD Monitoring

Ultrasensitive circulating tumor DNA assessment is being applied to predict and track response to immunotherapy and to detect relapse across multiple solid tumors. Monitoring resistance mutations such as ESR1 during minimal residual disease testing is also a focus as recurrence emerges. At the American Association for Cancer Research (AACR) Annual Meeting 2026 in San Diego, new data will highlight detection depth and real-world performance across diverse patient cohorts. 

Personalis’ NeXT Personal ultrasensitive circulating tumor DNA (ctDNA) assay will be featured alongside the debut of Real‑Time Variant Tracker, a first-of-its-kind feature within tumor-informed clinical minimal residual disease (MRD) testing designed to longitudinally track therapy resistance mutations. The company and collaborators will present one oral session and three posters at AACR 2026, running April 17–22 in San Diego. The agenda includes colorectal cancer and non‑small cell lung cancer applications, with emphasis on prediction of response, relapse, and outcomes using serial ctDNA measurements.

An oral podium presentation, “Neoadjuvant pembrolizumab stratified by tumor mutation burden in high‑risk stage II–III dMMR/MSI colorectal cancer (NEOPRISM‑CRC): Perioperative ultrasensitive ctDNA monitoring and tumor‑infiltrating TCR repertoire for treatment response prediction,” will highlight the assay’s use for predicting and tracking response to neoadjuvant immunotherapy in colorectal cancer. A poster presentation on “Monitoring ESR1 and other mutations linked to resistance with a tumor‑informed MRD test” will present analytical validation and real‑world case studies of Real‑Time Variant Tracker for detecting resistance and other clinical mutations during MRD testing.

A second poster presentation will provide a deep analysis of real-world clinical performance across a large patient cohort, noting that NeXT Personal consistently achieved ultrasensitive ctDNA detection levels below 100 parts per million (ppm) and down to10 ppm across diverse solid tumor types, stages, and challenging testing conditions. A third poster describes ultrasensitive ctDNA monitoring to predict early immunotherapy response in recurrent metastatic non-small cell lung cancer.

“We are thrilled to present the first NeXT Personal data on the Real‑Time Variant Tracker. The AACR data highlights how tracking therapy resistance mutations like ESR1 during MRD testing has the potential to inform patient management once cancer recurrence is detected,” said Dr. Richard Chen, President and Chief Medical Officer at Personalis.

“In addition, the data presented at AACR further reinforces that ultrasensitive ctDNA detection with NeXT Personal can impact how colorectal cancer is monitored and managed. Both of these studies are examples of our unwavering commitment to innovation to drive better outcomes for patients," added Dr. Chen.

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