2026 ASCO Guidelines on ctDNA Testing: A Patient’s Guide to Liquid Biopsies

Quick Summary (TL;DR)

The American Society of Clinical Oncology (ASCO) has released an updated guideline on circulating tumor DNA (ctDNA) testing (often called a liquid biopsy) for patients with solid tumors and lymphoma. This simple blood test can detect cancer DNA to help guide treatment. The guidelines recommend ctDNA testing when standard tissue biopsies are too risky, when quick decisions are required, or when a targeted drug demands it. However, because liquid biopsies can miss some mutations, a negative blood test should always be confirmed with a traditional tissue biopsy.

Cancer care is rapidly shifting away from one-size-fits-all treatments toward highly personalized medicine. At the forefront of this revolution is a revolutionary blood test known as a liquid biopsy.

To clear up confusion and set a gold standard for care, a multidisciplinary expert panel—which intentionally included dedicated patient representatives—conducted a massive review of medical literature spanning from 2017 to 2025. The result is the definitive 2026 ASCO Guideline on Circulating Tumor DNA Testing in Solid Tumors and Lymphoma.

If you or a loved one is navigating a cancer diagnosis, here is a patient-friendly breakdown of what these new guidelines mean for your treatment journey.

What is ctDNA and a Liquid Biopsy?

When cancer cells grow and die, they shed tiny fragments of their genetic material into your bloodstream. These floating fragments are called circulating tumor DNA (ctDNA).

A liquid biopsy is a routine blood draw that captures and analyzes these fragments. By decoding this DNA, doctors can pinpoint the exact genetic mutations driving your cancer and match you with specialized, targeted therapies—potentially avoiding the need for invasive surgeries.

When Does ASCO Recommend a ctDNA Test?

The 2026 guidelines state that outside of formal clinical trials, a ctDNA test should only be ordered if the results will directly change your medical care. Specifically, the panel recommends liquid biopsies as a first assessment or a tissue replacement in three major scenarios:

• When a Tissue Biopsy is Too Risky: If a tumor is located deep inside an organ (like the brain or lung) where surgery or a needle biopsy poses a high physical risk, a blood test is a safe and effective alternative.
• When Time is of the Essence: Traditional surgical biopsies can take weeks to schedule, process, and analyze. If your cancer is aggressive and your medical team needs to choose a targeted therapy immediately, a ctDNA blood test can deliver answers much faster.
• When Required by Regulatory Indications: Many advanced, modern cancer medications are FDA-approved only for patients with specific genetic mutations. If a drug’s official approval allows or requires a liquid biopsy to prove you qualify, a ctDNA test is the standard path forward.

⚠️ The "False Negative" Catch: Why Tissue Biopsies Still Matter

It is critical for patients to understand that some tumors are "low shedders," meaning they do not drop much DNA into the blood. If your ctDNA test comes back negative, inconclusive, or contradicts what your doctor sees on a scan, the ASCO guidelines state that you must seek a traditional, tissue-based biopsy to double-check the results. A positive liquid biopsy is highly reliable, but a negative one cannot rule out a mutation entirely.

What ctDNA Testing is NOT Recommended For (Yet)

Because this technology is so exciting, many patients ask if a blood test can be used to track the exact percentage or concentration of cancer in their body over time.

The ASCO panel evaluated the data and concluded that fractional, percentage, or concentration-based measures of ctDNA are not currently recommended as a surrogate tool to track disease burden. Standard imaging scans and clinical exams remain the gold standards for monitoring whether a tumor is growing or shrinking.

However, the panel recognized that this is a rapidly evolving field. New data regarding Molecular Residual Disease (MRD)—testing for trace amounts of cancer left behind after surgery—is accumulating quickly, and tumor-specific updates are expected soon.

Questions to Ask Your Oncologist

If you have been diagnosed with a solid tumor or lymphoma, use these questions to advocate for your care at your next appointment:

1. Based on my cancer type, am I a good candidate for a ctDNA liquid biopsy?
2. Are we waiting on tissue biopsy results, and would a blood test give us actionable answers faster?
3. If my liquid biopsy comes back negative, what is our backup plan for a tissue biopsy?

Frequently Asked Questions (FAQ)

What are the 2026 ASCO guidelines for ctDNA testing?

The 2026 ASCO guidelines recommend circulating tumor DNA (ctDNA) tests for solid tumors and lymphoma if a traditional tissue biopsy is too risky, if rapid results are needed to guide immediate treatment, or if an FDA-approved drug requires a companion liquid biopsy diagnostic.

Can a liquid biopsy replace a tissue biopsy entirely?

Not entirely. While a positive liquid biopsy is incredibly useful for finding targeted treatments, it can yield false negatives if a tumor sheds low amounts of DNA. ASCO guidelines dictate that negative or inconclusive ctDNA results must be confirmed with standard tissue testing.

Can a blood test measure how much cancer is in your body?

No. The updated ASCO guidelines do not support using percentage or concentration-based measures of total cell-free DNA to track overall tumor size or disease burden outside of highly specific clinical trial protocols.

Disclaimer: This article is a public-friendly summary of the 2026 ASCO Guideline ("Circulating Tumor DNA Testing in Solid Tumors and Lymphoma"). It is intended for educational purposes only and does not replace professional medical advice. Always consult your oncologist regarding diagnostic testing and treatment choices.