Venous thromboembolism (VTE) represents a significant clinical challenge in the management of oncological patients, often leading to increased morbidity and poorer survival outcomes. Among various malignancies, colorectal cancer (CRC) stands out due to its high incidence of thrombotic complications. In the specific context of locally advanced rectal cancer (LARC), identifying patients at high risk for thrombosis remains a priority for clinicians. Emerging research now suggests that ctDNA and VTE risk are closely linked, offering a potentially powerful biomarker for risk stratification. By analyzing circulating tumor DNA (ctDNA) at baseline, medical professionals might better predict which patients are likely to develop deep vein thrombosis or pulmonary embolism during their treatment journey. This advancement is particularly relevant in the Indian clinical setting, where the burden of colorectal cancer is rising and personalized medicine is becoming the standard of care.

Understanding the Role of ctDNA in Cancer Prognosis

Circulating tumor DNA has rapidly transformed from a research curiosity into a vital tool for managing solid tumors. These small fragments of DNA, shed into the bloodstream by apoptotic or necrotic tumor cells, provide a real-time snapshot of the genomic landscape of a malignancy. In locally advanced rectal cancer, clinicians primarily use ctDNA to detect minimal residual disease (MRD) and monitor the response to neoadjuvant chemoradiation. However, its utility extends beyond simple detection. The quantity of ctDNA, often measured as the variant allele frequency (VAF), serves as a surrogate for total tumor burden and biological aggressiveness. When the tumor burden is high, the systemic inflammatory response and the release of procoagulant factors often increase. Consequently, higher ctDNA levels may reflect a more hypercoagulable state. This study aimed to investigate whether these genetic markers could serve as early warning signs for thromboembolic events, which are traditionally difficult to predict using standard clinical parameters alone. Understanding this relationship allows oncologists to move beyond the one-size-fits-all approach to thromboprophylaxis.

The Significance of ctDNA and VTE Risk in Rectal Cancer

The prospective study conducted at the European Institute of Oncology (IEO) provided compelling evidence regarding the association between ctDNA and VTE risk. By analyzing sixty-one patients with LARC, the researchers categorized individuals into VAF-high and VAF-low groups based on median baseline values. Over a follow-up period of 58 months, the results showed that 15% of the cohort experienced a VTE event. Notably, patients in the VAF-high group demonstrated a much higher cumulative incidence of VTE compared to those in the VAF-low group. The hazard ratio of 2.42, although exploratory, indicates a strong trend toward increased risk in patients with higher baseline tumor DNA levels. Furthermore, when comparing ctDNA-positive patients to those who were ctDNA-negative at baseline, the hazard ratio climbed to 5.70. These findings suggest that the presence of detectable tumor mutations in the plasma is not merely a marker of cancer presence but also a harbinger of vascular complications. For clinicians in India, where access to advanced genomic testing is expanding, these insights provide a compelling argument for integrating liquid biopsies into routine preoperative assessments.

Exploring the KRAS Mutation and Thrombotic Tendencies

Perhaps the most striking finding of the research involves the role of specific genetic mutations, particularly KRAS. In the subgroup of patients with KRAS-mutant rectal cancer, the study found a highly significant correlation between baseline ctDNA levels and VTE. Interestingly, all observed VTE events in this subgroup occurred exclusively in patients with high baseline VAF. This suggests a synergistic effect where the KRAS mutation, known for its role in upregulating tissue factor and other procoagulant pathways, combines with a high tumor burden to create a perfect storm for thrombosis. Tissue factor is a primary initiator of the coagulation cascade, and its expression is often higher in tumors with KRAS mutations. Consequently, the combination of a high-risk mutation and a high volume of circulating DNA fragments may serve as a definitive marker for mandatory thromboprophylaxis. This level of genetic insight allows for a more nuanced understanding of why certain patients fail traditional preventive measures. Therefore, identifying KRAS status alongside ctDNA levels could become a cornerstone of personalized supportive care in oncology.

Clinical Utility of VAF-Based Risk Stratification

Incorporating VAF-based stratification into clinical practice could significantly refine our approach to managing LARC. Currently, many clinicians rely on the Khorana score to assess VTE risk, yet this tool often lacks sensitivity in specific gastrointestinal cancers. By using baseline ctDNA as a dynamic biomarker, doctors can more accurately identify patients who fall into a high-risk category despite having a low Khorana score. In the Indian context, where healthcare resources must be utilized efficiently, targeting expensive or intensive anticoagulation therapy toward those with high VAF and KRAS mutations could optimize patient outcomes while minimizing bleeding risks. Moreover, the study utilized droplet digital PCR, a technology that is increasingly available in specialized diagnostic centers across India. This accessibility ensures that the transition from research findings to clinical application is feasible. If validated in larger cohorts, ctDNA assessment could become as routine as staging imaging. Transitioning to this molecularly-guided approach will likely reduce the incidence of unexpected VTE, which remains a leading cause of death and treatment interruption in cancer patients globally.

Moving Toward Validated Biomarkers for Thrombosis

While the findings from this prospective study are promising, they represent an exploratory step that requires further validation. The relatively small sample size of 61 patients highlights the need for larger, multi-center trials to confirm the statistical significance of these hazard ratios. Nevertheless, the biological plausibility of the link between ctDNA, KRAS mutations, and thrombosis is strong. Future research should also investigate whether changes in ctDNA levels during treatment, such as after neoadjuvant chemoradiation, can further refine the risk of VTE. As we move toward a more integrated model of oncology care, the fusion of liquid biopsy data with clinical risk factors will likely provide the most accurate predictive models. For now, the association between high baseline ctDNA and increased VTE occurrence serves as a crucial reminder of the systemic impact of localized rectal cancer. Clinicians should maintain a high index of suspicion for VTE in patients presenting with high tumor-specific VAF. Ultimately, this research paves the way for a new era where genomic surveillance protects patients not just from cancer progression, but also from the life-threatening complications of the disease.

Frequently Asked Questions

What is the relationship between ctDNA and VTE risk in rectal cancer patients?

Current research suggests that higher baseline circulating tumor DNA (ctDNA) levels, measured as variant allele frequency (VAF), are associated with an increased risk of venous thromboembolism (VTE). Patients with high VAF or detectable ctDNA have a higher cumulative incidence of thrombotic events compared to those with low or negative levels. This relationship is thought to reflect the systemic procoagulant state associated with a higher tumor burden and specific oncogenic mutations.

How does the KRAS mutation specifically impact the risk of developing a blood clot?

The KRAS mutation is a significant driver of hypercoagulability because it often upregulates the expression of tissue factor, a key protein in the blood-clotting process. In the context of locally advanced rectal cancer, patients with both a KRAS mutation and high baseline ctDNA levels appear to be at the highest risk. In recent studies, all VTE events in the KRAS-mutant group occurred in patients with high baseline variant allele frequencies.

Can ctDNA testing be used to decide which patients need anticoagulation?

While ctDNA testing shows great potential as a predictive biomarker for VTE, it is currently considered exploratory. Clinicians may use high ctDNA levels as an additional risk factor when evaluating a patient's overall thrombotic profile. However, it should not yet replace established clinical guidelines or validated risk scores like the Khorana score. Larger prospective trials are necessary to confirm if ctDNA-guided anticoagulation can safely and effectively reduce VTE rates in cancer patients.

Disclaimer: This content is for informational and educational purposes only and does not constitute medical advice, diagnosis, or treatment. Always seek the advice of a physician or other qualified health provider with any questions regarding a medical condition. Refer to the latest local and national guidelines for clinical practice.

References

Gervaso L et al. Circulating tumor DNA to predict the risk of venous thromboembolism in locally advanced rectal cancer. Cancer Treat Res Commun. 2026 Jul 17. doi: undefined. PMID: 42468056.