Stereotactic ablative radiation therapy for renal cell carcinoma with inferior vena cava tumor thrombus

Abstract

Background: Inferior vena cava tumor thrombus (IVC-TT) is a rare yet deadly sequel of renal cell carcinoma (RCC) with limited treatment options. The standard treatment is extirpative surgery, which has high rates of morbidity and mortality. As a result, many patients are unfit or unwilling to undergo surgery and face poor prognosis. This stresses the need for alternative options for local disease control. Our study aims to assess the feasibility and oncological outcomes of stereotactic ablative radiation (SAbR) for IVC-TT.

Methods: A retrospective study reviewing six leading international institutions' experience in treating RCC with IVC-TT with SAbR. Primary end point was overall survival using Kaplan-Meier.

Results: Fifteen patients were included in the cohort. Over 50% of patients had high level IVC-TT (level III or IV), 66.7% had metastatic disease. Most eschewed surgery due to high surgical risk (7/15) or recurrent thrombus (3/15). All patients received SAbR to the IVC-TT with a median biologically equivalent dose (BED₁₀) of 72 Gy (range: 37.5-100.8) delivered in a median of 5 fractions (range 1-5). Median overall survival was 34 months. Radiographic response was observed in 58% of patients. Symptom palliation was recorded in all patients receiving SAbR for this indication. Only grade 1 to 2 adverse events were noted.

Conclusions: SAbR for IVC-TT appears feasible and safe. In patients who are not candidates for surgery, SAbR may palliate symptoms and improve outcomes. SAbR may be considered as part of a multimodal treatment approach for patients with RCC IVC-TT.

Keywords: Inferior vena cava thrombus; Radiation; Renal cell carcinoma; Sbrt; T3b.

Figure 1:

SAbR treatment plan and assessment of treatment response with multi-parametric MRI in a 38 year-old female with renal cell carcinoma, tumor thrombus in the inferior vena cava (IVC-TT) and Budd-Chiari syndrome. (A) Staging MRI at diagnosis. Coronal T2-weighted image demonstrates IVC-TT (arrowheads) with distal tip extending beyond the diaphragm (arrow). Axial T2-weighted image with fat suppression (Ax T2 FS) demonstrates expansion and complete filling of the IVC lumen and ascites (arrowheads). Contrast-enhanced T1-weighted gradient echo images during the arterial (art) and venous (venous) phases after administration of a bolus of gadobutrol (0.1. mmol/kg body weight) demonstrates heterogeneous enhancement of the IVC-TT (red arrow). Note decreased heterogeneous enhancement of the posterior right lobe of the liver (arrowheads) due to congestion caused by bland (i.e., non-enhancing) thrombus in the right hepatic vein (white arrow). The left and middle hepatic veins (white arrowhead) are patent. Axial image acquired at a lower level shows heterogeneous infiltrating primary tumor in the left kidney (yellow arrow). LFT’s at presentation were ALT 241U/L, AST 165 U/L ALK Phos 186 U/L. SAbR of 40 Gy (B) aimed at the IVC-TT was delivered in 5 fractions. Follow-up imaging at 6 weeks (C) and 7 months (D) shows a clear reduction in both the diameter and the length of the IVC-TT. Absence of enhancement in the IVC-TT at 7 months suggests a predominantly non-viable tumor thrombus. Note also progressive decrease in ascites and recanalization of a posterior branch of the right hepatic vein (black arrowhead) with persistent bland thrombus in an anterior branch of the hepatic vein (white arrow). LFT’s improved and normalized within 6 weeks of SAbR. RCC- Renal cell carcinoma, IVC-TT – Inferior Vena Cava tumor thrombus, Ax- axial, Cor- coronal, T2 – T2-weighted single shot fast spin echo imaging, T2 FS – T2-weighted single shot fast spin echo imaging with fat suppression, ART – T1-weighted gradient echo imaging during the arterial phase, VEN – T1-weighted gradient echo imaging during the venous phase, LFT – Liver Function Tests, ALT - Alanine Transaminase, AST - Aspartate Aminotransferase, ALK Phos – Alkaline Phosphatase, SAbR – Stereotactic Ablative Radiation, DVH – Dose Volume Histogram, PTV – Planning Target Volume.