ASCO 2026 was not defined by a single next-generation sequencing (NGS) story.

Across the ASCO Annual Meeting and ASCO Breakthrough sessions, three themes stood out: molecular testing is moving earlier in the treatment pathway, liquid biopsy research is expanding beyond circulating tumor DNA (ctDNA), and alternative biofluids are being evaluated for cancers where plasma may not be the most informative sample.

For years, molecular testing has often been framed around baseline tumor profiling: identify a targetable alteration, match an available therapy, and start treatment. Now research presented at ASCO 2026 suggests a broader clinical role for molecular testing, not as a one-time result, but as a decision tool used at defined clinical timepoints.

The question is no longer only whether a tumor can be sequenced. It is when to test, which analyte and sample to use, and how the result should inform the next clinical step. 

Molecular Testing Is Moving Earlier

LIBRETTO-432 asked whether RET-directed therapy could be evaluated earlier, after resection, in patients with stage IB-IIIA RET fusion-positive non-small cell lung cancer (NSCLC). [1]

• In the phase 3 trial, the reported 2-year event-free survival rate was 91.5% with adjuvant selpercatinib versus 61.1% with placebo in patients with stage II-IIIA disease. [1]

These findings place molecular testing upstream of adjuvant treatment selection. In resected disease, identifying RET fusion status may become relevant not only at recurrence, but before post-surgical systemic treatment is considered. [1] 

CIRCULATE addressed a different early-stage question: whether postoperative ctDNA could identify a subgroup of patients with proficient mismatch repair (pMMR), microsatellite-stable (MSS) stage II colon cancer who may benefit from adjuvant chemotherapy.

• In the ctDNA-positive per-protocol population, the reported 3-year recurrence rate was 19% with adjuvant chemotherapy versus 62% with observation. [2] 

The interpretation requires caution. Although the treatment effect was large, the randomized ctDNA-positive subset was small, and recruitment closed early. These results should be interpreted in the context of the assay, study design, and prospective validation pathway. [2]

Earlier testing also overlaps with longitudinal monitoring.

In hormone receptor-positive, HER2-negative advanced breast cancer, SERENA-6 used serial ctDNA testing to detect emergent ESR1 mutations before radiographic progression. Patients were then randomized to switch endocrine therapy or continue their current aromatase inhibitor-based regimen. 

• The reported median progression-free survival 2 (PFS2) was 25.7 months with switched endocrine therapy compared to 19.1 months with continued aromatase inhibitor-based regimen. [3] 

Similarly, a longitudinal ctDNA biomarker study in patients with advanced solid tumors receiving immune checkpoint inhibitors reported that molecular progression preceded radiographic progression by a median of 63.5 days and was associated with worse progression-free and overall survival. [4]

These studies do not replace imaging. They suggest that, in selected settings, molecular change may provide an earlier layer of information than structural change alone.[3,4]

Expanding the Reach of Liquid Biopsy With ctRNA

ctDNA remains a central liquid biopsy analyte, but ASCO Breakthrough 2026 also highlighted the role of RNA-based signals. 

Published NSCLC data support the incorporation of circulating tumor RNA (ctRNA) alongside ctDNA for guideline-recommended rearrangement detection in metastatic NSCLC. [5] Beyond fusion detection, ctRNA may also help characterize gene-expression programs and tumor microenvironment signals that are not directly captured by DNA alterations alone. [6]

An exploratory ASCO Breakthrough 2026 study evaluated plasma ctRNA expression across 102 NSCLC samples, spanning treatment-naive and EGFR-mutant progressive cohorts. Plasma ctRNA captured immune and tumor microenvironment features, including immune phenotypes ranging from inflamed to immune-excluded patterns. In the EGFR-mutant progression cohort, transcriptional shifts were observed in pathways related to TGF-β signaling, extracellular matrix organization, DNA damage response, and immune regulation. [6]

The same analysis reported that tumor-derived epithelial ctRNA correlated with ctDNA tumor fraction, and that transcriptomic signal remained quantifiable in a subset of samples that were negative for ctDNA mutations. [6]

DNA can identify genomic alterations. RNA can show what is being expressed. In selected clinical contexts, both layers may be informative. [5,6]

Alternative Biofluids May Offer a Clearer Window to Specific Cancers

Liquid biopsy is not confined to plasma. ASCO Breakthrough 2026 also featured urine testing for genitourinary cancers. [7]

A phase 1/2 study evaluated a urine-based multi-cancer early detection assay in localized prostate, bladder, and kidney cancers using paired urine and blood samples from patients, as well as healthy and benign controls. The interim analysis reported adequate DNA yield from all urine samples and no cancer-associated alterations in controls. [7]

Urine ctDNA identified cancer-associated alterations in 92.3% of bladder cancer cases compared with 15.4% in plasma. In prostate cancer, detection increased from 6.7% with urine ctDNA alone to 40.0% with combined urine ctDNA and ctRNA analysis. For kidney cancer, urine showed improved detection over blood, but overall sensitivity remained modest at 14.3%. [7]

These findings support a sample-matching principle. Alternative biofluids may be most useful when the sample is biologically closer to the tumor, but performance can vary by cancer type, analyte, and clinical setting. [7] 

Interpretation and the Path Toward Better-Matched Testing

The ASCO 2026 data point to a practical shift in how liquid biopsy is being studied. NGS is no longer simply about whether more sequencing can be done. It is whether the right molecular signal can be measured at the point when it can inform care. 

In early disease, molecular profiling and postoperative ctDNA are being evaluated to guide adjuvant treatment decisions. During active treatment, serial ctDNA may detect emerging resistance or molecular progression before radiographic change. At progression, RNA and multi-analyte approaches may add transcriptomic and microenvironmental context. For selected tumors, urine may provide a more informative sample than plasma. [1-7]

These approaches remain at different stages of evidence. Their future role will depend on validation, clinical context, and whether the result leads to a clear next step. 

References

1. Wu YL, Hochmair M, Yang Y, et al. Selpercatinib in early-stage RET fusion-positive non-small-cell lung cancer. N Engl J Med. Published online May 31, 2026. doi:10.1056/NEJMoa2602628.

2. Folprecht G, et al. J Clin Oncol. 2026;44(17_suppl):LBA3500.

3. Bidard FC, et al. J Clin Oncol. 2026;44(17_suppl):LBA1007.

4. Anees M, et al. J Clin Oncol. 2026;44(16_suppl):2572.

5. Samol J, et al. JCO Precis Oncol. 2025;9:e2500181.

6. Pek M, Poh J, Tan M-H. Characterizing plasma circulating tumor RNA landscape in advanced NSCLC: Preliminary insights into treatment resistance and tumor microenvironment. Paper presented at: ASCO Breakthrough; June 25-27, 2026; Singapore. Abstract 167.

7. Chen K, Tan M, Lim S, et al. Early results from a phase 1/2 clinical study of a urine-based multi-cancer early detection assay for prostate, bladder, and kidney cancers. Paper presented at: ASCO Breakthrough; June 25-27, 2026; Singapore. Abstract 181.