Interventional Management of Renal Cell Carcinoma with Inferior Vena Cava Tumor Thrombus and Secondary Deep Venous Thrombosis: A Case Report

Introduction

Epidemiology and Clinical Challenges

Renal cell carcinoma (RCC) accounts for approximately 2%–3% of malignancies in adults. In about 4%–10% of cases, the tumor extends into the venous system and forms an inferior vena cava tumor thrombus (IVCTT).¹ IVCTT is associated with poorer outcomes and increased mortality, driven largely by thromboembolic events, including pulmonary embolism (PE) and lower-extremity deep vein thrombosis (DVT). Symptomatic DVT has been reported in up to 40% of patients with IVCTT, reflecting the combined effects of venous outflow obstruction and tumor-related hypercoagulability.²

Therapeutic Challenges

For patients with resectable disease, radical nephrectomy with tumor thrombectomy remains the standard of care. However, recurrence after surgery is still reported in approximately 30%–40% of cases, and perioperative morbidity is substantial, including major hemorrhage and cardiopulmonary complications.³ For patients who are not surgical candidates, systemic therapy with tyrosine kinase inhibitors and immune checkpoint inhibitors may provide disease control, but responses of bulky venous tumor thrombi are often limited and clinically slow.⁴ Management of IVCTT-associated DVT is similarly complex. The 2023 CHEST guideline advises against routine inferior vena cava filter (IVCF) placement because tumor thrombus progression can lead to filter thrombosis or occlusion, and available evidence does not demonstrate durable clinical benefit.⁵ Catheter-directed thrombolysis (CDT) combined with anticoagulation is increasingly used to restore venous patency and relieve symptoms, but recurrent thrombosis remains common when the underlying tumor thrombus persists, with reported recurrence rates of approximately 25%–35%.⁶

Innovation and Theoretical Basis

Interventional oncology has expanded the range of localized treatments aimed at controlling IVCTT while minimizing systemic toxicity. Endoluminal brachytherapy with iodine-125 (^125I) seeds can deliver sustained low-dose irradiation (typically 20–60 Gy) to inhibit intravascular tumor growth and may reduce tumor thrombus burden.⁷ Building on this rationale, we describe a combined interventional approach that integrates ^125I seed-strand implantation with CDT and renal artery embolization (RAE) to concurrently address venous thrombosis and tumor-related obstruction.

Case Presentation

Ethics Statement

This retrospective case report was conducted in accordance with the Declaration of Helsinki. The need for formal ethics approval was waived by the Institutional Review Board of Tangdu Hospital because it involved the retrospective analysis of anonymized data from routine clinical care. Written informed consent was obtained from the patient for publication of this case report.

Patient Information

A 52-year-old man presented with progressive swelling and pain of the right lower limb for one month. He had no history of hypertension, diabetes mellitus, cardiovascular disease, or prior malignancy. There was no known family history of renal cell carcinoma or hereditary cancer syndromes.

Clinical Findings

On examination, the right lower limb showed pitting edema, with a calf circumference of 42 cm compared with 37 cm on the contralateral side. Homan’s sign was positive. No palpable abdominal mass was detected. Vital signs were within normal limits. The symptoms had developed insidiously approximately one month before presentation and had worsened steadily.

Diagnostic Assessment

At baseline (December 29, 2021), Contrast-enhanced computed tomography (CT) demonstrated a 5.0×4.1 cm heterogeneously enhancing mass in the mid-pole of the right kidney (Figure 1A). The lesion invaded the right renal vein and extended into the inferior vena cava (IVC), forming an approximately 8 cm tumor thrombus consistent with Mayo level II disease (Figure 1B). In addition, the right iliofemoral vein was completely occluded by thrombus (Figure 1C, as demonstrated on DSA).

Figure 1 Baseline imaging findings at presentation. (A) Axial contrast-enhanced computed tomography (CT) image demonstrates a heterogeneously enhancing mass in the mid-pole of the right kidney. (B) Coronal reformatted CT image shows the tumor thrombus (arrowheads) extending from the right renal vein into the inferior vena cava (IVC),consistent with a Mayo level II thrombus. (C) DSA image reveals complete occlusion of the right iliofemoral vein by thrombus (arrowheads), with the formation of collateral veins, consistent with secondary deep vein thrombosis (DVT).

The filling defect within the IVC (and involvement of the renal venous outflow) showed heterogeneous contrast enhancement on both arterial and venous phase imaging (Figure 1B), supporting the diagnosis of tumor thrombus rather than bland thrombus. In contrast, the occlusive thrombus in the iliofemoral venous system showed no appreciable enhancement (Figure 1C), consistent with secondary bland DVT. The iliofemoral thrombosis was considered multifactorial, related to impaired venous return from IVC obstruction and a tumor-associated hypercoagulable state. Laboratory evaluation showed a markedly elevated D-dimer level (5.2 mg/L; reference <0.5 mg/L). Renal function parameters, including serum creatinine and blood urea nitrogen, were within normal limits. Tumor and thrombus measurements were obtained from contrast-enhanced CT images. The primary renal mass was recorded using the longest axial diameter, and the craniocaudal extent of the IVC tumor thrombus was measured on coronal reformatted images. Response of the iliofemoral DVT was assessed using clinical symptom improvement, degree of venous recanalization on venography, and changes in limb circumference.Two independent radiologists performed all measurements, and the mean of their values was reported.

Therapeutic Intervention

A staged, multimodal interventional strategy was implemented in three sequential steps: catheter-directed thrombolysis (CDT) to restore venous outflow, endoluminal brachytherapy with ^125I seed strands to treat the inferior vena cava tumor thrombus (IVCTT), and renal artery embolization (RAE) to reduce tumor vascularity and burden.

Step 1: Catheter-Directed Thrombolysis (CDT)

Under local anesthesia, a 6-Fr thrombolysis catheter (UniFuse^®, AngioDynamics) was introduced through the right femoral venous access and positioned within the right iliac vein. Urokinase was infused continuously at 100,000 IU/day, with concurrent therapeutic anticoagulation using enoxaparin (1 mg/kg, twice daily) for 5 days. Daily venography demonstrated progressive thrombus dissolution.

Step 2: Implantation of Iodine-125 (^125I) Seed Strands

Device preparation. Twenty ^125I seeds (activity per seed: 0.8 mCi; half-life: 60 days) were loaded into an H1 catheter (Merit; 510035) at 1-cm intervals. The distal end of the catheter was sealed (Figure 2A). To maintain catheter integrity and provide longitudinal support, the excess catheter segment was reinforced using a 0.035-inch × 135-cm guidewire (GWS-35-260, Cook). The proximal end was then sealed with an infusion connector (Figure 2A).

Figure 2 Preparation and deployment of the ^125^I seed strands. (A) Photograph of the self-designed long ^125^I seed strand prior to implantation, showing the seeds loaded at 1-cm intervals within a sealed catheter. (B) Intraoperative digital subtraction angiography (DSA) image confirms the deployment of two ^125^I seed strands (arrows) within the inferior vena cava, positioned along the tumor thrombus. (C) External view illustrates the stable final position of both implanted seed strands, with their proximal ends secured at the jugular access site(red arrows).

Deployment. Following completion of thrombolysis, two customized long ^125I seed strands were assembled. Under digital subtraction angiography (DSA) guidance, the first strand was positioned along the residual IVCTT within the inferior vena cava. A second strand was deployed in parallel to the first to achieve full longitudinal coverage of the thrombus, with positioning confirmed on intraoperative DSA (Figure 2B). Both strands were secured externally at the jugular access region and fixed to the skin of the neck using non-absorbable sutures to minimize the risk of migration; the surface projection is shown in Figure 2C.

Step 3: Renal Artery Embolization (RAE)

Superselective catheterization of the right renal artery trunk was performed (Figure 3A). Embolization was carried out sequentially using 300–500 μm polyvinyl alcohol (PVA) particles followed by gelatin sponge to occlude tumor-feeding arterial branches. Completion angiography confirmed effective devascularization of the tumor (Figure 3B).

Figure 3 Renal artery embolization (RAE) procedure. (A) Pre-embolization angiogram via superselective catheterization of the right renal artery shows the tumor vasculature. (B) Post-embolization completion angiogram after administration of polyvinyl alcohol (PVA) particles and gelatin sponge confirms successful devascularization of the renal tumor.

Figure 2B: Fluoroscopic image demonstrating deployment of two ^125I seed strands (arrows) within the inferior vena cava.

Figure 2C: Post-procedure plain radiograph confirming stable positioning of both seed strands.

Follow-Up and Outcomes

Objective Treatment Response

Treatment response to the combined interventional strategy was assessed using serial clinical examinations and cross-sectional imaging, with key findings summarized in Table 1.

Table 1 Timeline of Follow-Up Assessments

Figure 4 Follow-up imaging demonstrating treatment response of the inferior vena cava tumor thrombus (IVCTT). (A) One-month follow-up coronal computed tomography (CT) scan showing marked regression of the IVCTT (arrow). (B) Three-month follow-up axial CT scan showing further reduction in the size of the IVCTT (arrow).

Primary Renal Tumor Response

At baseline (December 29, 2021), contrast-enhanced CT showed a heterogeneously enhancing right renal mass measuring 5.0×4.1 cm (Figure 1A). At the first follow-up CT performed 1 month after the procedure (January 29, 2022), the longest axial diameter decreased to 3.5 cm, corresponding to an approximately 30% reduction. At 3 months (March 29, 2022), the lesion remained stable, measuring 3.5×3.0 cm.

Inferior Vena Cava Tumor Thrombus (IVCTT) Response

At baseline, the IVCTT measured approximately 8.0 cm in craniocaudal extent (Mayo level II; Figure 1B). At month 1 (January 29, 2022), follow-up CT demonstrated regression to 3.0 cm (approximately 62.5% decrease; Figure 4A). At month 3 (March 29, 2022), the IVCTT further decreased to 1.5 cm (Figure 4B), with subsequent imaging showing continued stability without re-expansion.

Iliofemoral Deep Vein Thrombosis (DVT) Response

At presentation, the patient had marked right lower-limb edema, with a calf circumference of 42 cm on the right versus 37 cm on the left. After CDT, on January 4, 2022, the calf circumference had decreased to 38.5 cm. At month 1 (January 29, 2022), swelling and pain had resolved and the limb circumferences were nearly symmetric (approximately 37.5 cm bilaterally). We also clarified the involved vascular territory as the right iliofemoral venous system and revised the text to present the follow-up findings in direct alignment with the corrected timepoints.

Safety and Adverse Events

No major procedure-related complications were observed during hospitalization or follow-up, including clinically significant bleeding, infection, seed-strand migration, or symptomatic pulmonary embolism. Hemoglobin remained stable, with a nadir of 120 g/L and no requirement for transfusion. Renal function was preserved (creatinine 78 μmol/L at baseline and 82 μmol/L at 1 month).

Adjuvant Systemic Therapy

Adjuvant therapy with sunitinib was initiated 1 month after the procedure at 50 mg orally once daily on a 4-weeks-on/2-weeks-off schedule. Treatment was well tolerated; the only reported adverse event was grade 1 hand–foot skin reaction, managed conservatively without dose reduction or interruption. Sunitinib was continued at full dose throughout the more than 39-month follow-up period to maintain disease control in the setting of sustained radiographic response and minimal toxicity.

Patient Perspective

The patient reported substantial improvement in quality of life after treatment, particularly due to the marked reduction in lower-limb swelling and associated discomfort. He noted that these improvements enabled him to resume routine daily activities. Written informed consent was obtained for publication of this case report, including permission to use anonymized clinical data and imaging materials for educational and scientific purposes.

Discussion

Summary of Key Findings

This case describes a multimodal interventional strategy for renal cell carcinoma (RCC) with inferior vena cava tumor thrombus (IVCTT) complicated by secondary iliofemoral deep vein thrombosis (DVT). A staged protocol combining catheter-directed thrombolysis (CDT), endoluminal brachytherapy using customized long iodine-125 (^125I) seed strands, and renal artery embolization (RAE) was associated with rapid symptomatic improvement, substantial radiographic regression of the IVCTT, restoration of venous outflow, and durable local control during 40 months of follow-up.

Comparison with Existing Literature

Radical nephrectomy with thrombectomy remains the standard option for resectable IVCTT, but perioperative morbidity and recurrence rates remain clinically meaningful, particularly in complex thrombus anatomy or medically frail patients^8. In parallel, inferior vena cava filter (IVCF) placement is generally discouraged in IVCTT because progressive tumor thrombus may precipitate filter thrombosis, occlusion, or device-related complications.⁸ Prior studies support the feasibility of intravascular brachytherapy using ^125I seeds for tumor thrombus control;^9,10 however, achieving adequate longitudinal dose coverage can be technically challenging when the thrombus is extensive. In this context, the use of long, customizable seed strands offers a practical method to span the full thrombus length and mitigate underdosing at the cranial and caudal margins. Consistent with reports suggesting that embolization may enhance local tumor control and reduce tumor vascularity,^11,12 RAE in this case appeared to complement brachytherapy by decreasing arterial inflow to the primary renal mass and potentially limiting continued tumor extension into the venous system.

Pathophysiological Rationale for a Combined Approach

IVCTT contributes to morbidity through interrelated mechanisms: mechanical obstruction of venous return, activation of a tumor-associated hypercoagulable state, and progressive intravascular tumor growth. Addressing only the bland thrombus component may provide transient symptomatic benefit but leaves the underlying venous tumor burden untreated, which can perpetuate obstruction and increase the risk of recurrent thrombosis. Accordingly, the therapeutic design in this case targeted both components: CDT and anticoagulation were used to rapidly relieve venous occlusion, whereas endoluminal brachytherapy and RAE were intended to reduce the intravascular tumor burden and its driving hemodynamic and prothrombotic effects.

Avoiding Filter-Related Complications

In patients with IVCTT, IVCF placement may be complicated by device thrombosis, occlusion, and filter penetration, particularly when the tumor thrombus progresses.¹³ In this protocol, endoluminal ^125I seed strands were used to treat the IVCTT directly rather than introducing a permanent mechanical barrier within a tumor-involved segment of the IVC. If a biodegradable carrier or sheath (for example, a PGA-based structure) is used in this setting, it may further reduce concerns related to long-term intravascular foreign-body retention that have been raised for permanent devices.¹⁴ Collectively, this approach seeks to reduce embolic and occlusive risk by modifying the tumor thrombus itself rather than relying on a filter-based strategy.

Key Advantages of Long ^125I Seed Strands

First, ^125I provides sustained low-dose-rate irradiation because of its approximately 60-day half-life, enabling prolonged local treatment of intravascular tumor over several months. Prior work has reported meaningful tumor thrombus shrinkage after endovascular seed-strand brachytherapy without a high incidence of radiation-related vascular injury.¹⁵ Second, when delivered via a biodegradable or otherwise atraumatic carrier, seed-strand implantation can potentially lower the risk of chronic endothelial irritation compared with permanent metallic intravascular implants.¹⁶ Third, long strands can be tailored to thrombus length and vessel anatomy, which may improve longitudinal coverage and dose uniformity, including within curved venous segments.¹⁷

Clinical Implications

Taken together, the present case supports a conceptual framework in which CDT rapidly restores patency and symptom relief, while brachytherapy and RAE provide longer-term control of the intravascular tumor component that drives venous obstruction and recurrent thrombosis. Although a single case cannot establish efficacy, the sustained radiographic stability and absence of major procedure-related complications suggest that this integrated strategy may be considered in carefully selected patients who are poor surgical candidates or require urgent symptom relief from severe venous obstruction.

Limitations

The principal limitation of this report is that it describes a single patient. Although the clinical and radiographic responses were favorable, a case report cannot establish efficacy, define safety profiles, or determine how this strategy compares with standard management. The 40-month progression-free survival reflects the observed course of this individual patient and should not be interpreted as a predictable or generalizable outcome. Accordingly, the findings should be regarded as hypothesis-generating and warrant confirmation in larger cohorts and prospective studies.

Several Additional Considerations Merit Emphasis

Radiation dose planning and optimization: In this case, the estimated cumulative brachytherapy dose was approximately 80 Gy. However, optimal dosing is likely to depend on thrombus volume, geometry, and proximity to adjacent radiosensitive structures. Individualized dose planning, potentially incorporating functional or metabolic imaging to better characterize active tumor burden, may improve treatment precision and effectiveness.¹⁸

Long-term vascular safety: Preclinical data suggest that endovascular brachytherapy can be associated with localized venous wall changes, including fibrosis. Longitudinal surveillance is therefore essential to evaluate IVC patency, endothelial integrity, and the risk of delayed stenosis or occlusion, particularly in patients with prolonged survival.

Cost and resource implications: While interventional strategies may reduce operative morbidity and hospital resource utilization compared with major surgery, customized seed-strand fabrication and specialized procedural requirements may increase direct costs. Formal cost-effectiveness analyses will be needed to evaluate the overall value of this approach across different healthcare settings.

Conclusion

This case indicates that a multimodal interventional strategy integrating catheter-directed thrombolysis, endoluminal ^125I seed-strand brachytherapy, and renal artery embolization may be feasible in selected patients with RCC complicated by IVCTT and secondary DVT, particularly when surgery is not suitable or when rapid relief of venous obstruction is required. Although the observed outcome was favorable, broader evaluation is needed. Future prospective studies and well-characterized case series should focus on patient selection criteria, procedural standardization, dosimetric optimization, and long-term vascular and oncologic outcomes.