At the 2026 annual meeting of the American Association for Cancer Research (AACR), researchers from Memorial Sloan Kettering Cancer Center (MSKCC) presented new evidence that a blood-based biomarker, combined with advanced imaging, could enable real-time adjustment of cancer treatment in patients with HPV-related throat cancer. Findings from this clinical study (NCT03323463) highlight a potentially important shift in care, particularly for HPV-associated oropharyngeal cancer, a disease with generally high cure rates but ongoing efforts to reduce treatment-related toxicity. Rather than waiting until therapy is complete, clinicians may be able to tailor treatment intensity based on early indicators of response.
Circulating tumor DNA (ctDNA) has already shown promise for detecting minimal residual disease (MRD), but its role in guiding treatment decisions during therapy remains largely unexplored. To address this gap, a research team led by Bill H. Diplas, MD, PhD, a radiation oncology fellow at MSKCC, investigated whether serial ctDNA measurements, paired with weekly MRI scans, could provide a more precise and dynamic view of tumor response. In collaboration with Labcorp and Biocartis, the MSKCC researchers developed a personalized ctDNA assay that combined two strategies: detection of patient-specific tumor mutations and quantification of DNA from high-risk HPV strains, particularly HPV-16 and HPV-18, using anchored multiplex PCR and high-throughput sequencing.
The study enrolled 158 patients with HPV-associated oropharyngeal cancer who had undergone primary tumor resection followed by risk-adapted chemoradiotherapy guided by hypoxia assessment. MRIs were performed pretreatment and weekly following treatment to determine tumor volume, and blood samples were collected before treatment and weekly during therapy, yielding nearly 1,000 samples from 119 patients (mean 8.2 samples/patient) up to 126 weeks.
At baseline, ctDNA was identified in 93.9% of patients—outperforming either mutation-based (89.4%) or HPV-based (80.3%) methods alone. ctDNA levels also correlated with tumor size and biological features such as cell death and viral load. Notably, ctDNA emerged as a faster and more sensitive indicator of treatment response than imaging. Changes in ctDNA levels appeared earlier and across a broader dynamic range than tumor size reductions observed on MRI. By the second week of therapy, ctDNA measurements could already distinguish patients likely to require more intensive treatment.
The identification of patients with high-risk disease was significantly improved by combining on-treatment ctDNA assessment with imaging in a multimodal model, outperforming any modality alone. These results underscore the complementary nature of molecular signals in blood and structural changes seen on imaging.
Similar multimodal strategies that integrate ctDNA with imaging have been explored in other cancers, including breast and lung, primarily in research settings. Studies suggest that combining these approaches can improve prediction of treatment response and enable earlier detection of resistance. Broader analyses across colorectal, lung, and breast cancers further support the value of integrating molecular and imaging data to refine models of response and survival. However, most of these approaches remain investigational, and the use of ctDNA to guide real-time treatment decisions is only beginning to be tested in prospective trials.
Although further validation is needed, this study establishes a framework for real-time, personalized treatment in oropharyngeal cancer. If translated into clinical practice, such an approach could accelerate the shift toward adaptive therapy—where decisions are guided not only by how tumors appear on imaging, but by how they respond at the molecular level throughout treatment.
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