Sporadic versus Tuberous Sclerosis Complex–Associated Angiomyolipomas: Predictors for Long-Term Outcomes following Transcatheter Embolization

The radiomics-clinical nomogram for predicting the response to initial superselective arterial embolization in renal angiomyolipoma, a preliminary study

Purpose

The aim of this study was to explore a radiomics-clinical model for predicting the response to initial superselective arterial embolization (SAE) in renal angiomyolipoma (RAML).

Materials and methods

A total of 78 patients with RAML were retrospectively enrolled. Clinical data were recorded and evaluated. Radiomic features were extracted from preoperative contrast-enhanced CT (CECT). Least absolute shrinkage and selection operator (LASSO) and intra- and inter-class correlation coefficients (ICCs) were used in feature selection. Logistic regression analysis was performed to develop the radiomics, clinical, and combined models where the fivefold cross-validation method was used. The predictive performance and calibration were evaluated by the receiver operating characteristic (ROC) curve and calibration curve. Decision curve analysis (DCA) was used to measure clinical usefulness.

Results

The tumor shrinkage rate was 29.7% in total, and both fat and angiomyogenic components were significantly reduced. In the radiomics model, 12 significant features were selected. In the clinical model, maximum diameter (p = 0.001), angiomyogenic tissue ratio (p = 0.032), aneurysms (p = 0.048), and post-SAE time (p = 0.002) were significantly associated with greater volume reduction after SAE. Because of the severe linear dependence between radiomics signature and some clinical parameters, the combined model eventually included Rad-score, aneurysm, and post-SAE time. The radiomics-clinical model showed better discrimination (mean AUC = 0.83) than the radiomics model (mean AUC = 0.60) and the clinical model (mean AUC = 0.82). Calibration curve and DCA showed the goodness of fit and clinical usefulness of the radiomics-clinical model.

Conclusions

The radiomics-clinical model incorporating radiomics features and clinical parameters can potentially predict the positive response to initial SAE in RAML and provide support for clinical treatment decisions.

Long-term efficacy of selective arterial embolisation of renal angiomyolipoma

OBJECTIVE

To evaluate the long-term efficacy of selective arterial embolisation in renal angiomyolipoma (AML), with emphasis on tumour shrinkage, potential regrowth and the necessity of supplementary procedures.  Material and methods: A retrospective review of all 58 consecutive embolisations at two institutions, between 1999 and 2018, was performed. Clinical notes, laboratory data and imaging were reviewed.

RESULTS

The overall complication rate was 6.8%, with no Clavien-Dindo grades III-V complications. Kidney function was unaffected by embolisation as measured by creatinine. Median radiological follow-up was 4.8 years (interquartile range [IQR]: 2.8-7.8), and median clinical follow-up was 7.5 years (IQR: 4.7-14.0). Decreasing AML size was observed in 96% of procedures. Maximal shrinkage (30% median diameter decrease; IQR: 15-44) was reached after median 2.2 years (IQR: 0.6-4.8). During follow-up, regrowth occurred in 38% of patients, and four bleeding episodes occurred in three patients with tuberous sclerosis. Growing size and/or rebleeding prompted a redo embolisation in 9% of spontaneous AML and 50% of tuberous sclerosis-associated AML.

CONCLUSIONS

Being a well-tolerated treatment with few complications, selective arterial embolisation renders a pronounced size-reduction in most patients with AML, and kidney function is preserved. Regrowth is common, and a radiological follow-up is necessary. Tuberous sclerosis is a risk factor for the need of reintervention.

Long-term volume reduction in renal angiomyolipomas embolized by gelatin sponge particles with or without supplementary microcoil embolization

OBJECTIVE

To examine the effect of supplementary microcoil embolization on the long-term progression of angiomyolipomas embolized using gelatin sponge particles (GSPs).

METHODS

This retrospective study included 29 unruptured angiomyolipomas in 25 patients, treated by complete embolization and radiological follow-up for ≥3 years. Embolization was performed using GSPs and supplementary microcoils. Supplementary microcoil embolization affecting >90% of the tumor vasculature was defined as microcoil embolization. Tumor volumes pre- and post-embolization were measured by computed tomography or magnetic resonance imaging.

RESULTS

Eleven tumors received supplementary microcoil embolization and 18 tumors did not. Relative tumor reduction at >3 years post-embolization was significantly greater in tumors with supplementary microcoil embolization compared with tumors without microcoil embolization (81% ± 8% vs. 55% ± 29%). Fourteen tumors tended to show volume regrowth and the volumes of the remaining 15 tumors continued to decline. Tumors without supplementary microcoil embolization were more likely to show volume regrowth during follow-up than tumors with supplementary microcoil embolization (78% vs. 0%, respectively).

CONCLUSIONS

When using a combination of GSPs and microcoils, supplementary microcoil embolization should be carried out to ensure maximum long-term reduction in tumor volume in patients with angiomyolipomas.

Prophylactic Steroids for Preventing Postembolization Syndrome after Transcatheter Arterial Embolization of Renal Angiomyolipoma: A Comparative Study

Purpose

Postembolization syndrome (PES) after renal arterial embolization (RAE) can reduce the patient's tolerance of the procedure and extend the length of hospital stay. We aimed to assess the efficacy of steroid administration in preventing PES in patients undergoing RAE for angiomyolipoma (AML).

Material and Methods

Between May 2004 and March 2020, 29 RAE procedures in 26 patients with AML were performed. Patient information, including age, sex, tumor size, tuberous sclerosis complex-associated/sporadic AML, hemorrhagic/nonhemorrhagic AML, embolic material, steroid use, medication type, some blood laboratory parameters, hospital stay, and PES occurrence were retrospectively obtained. The prophylactic steroid protocol used in the study was as follows: 250 mg of intravenous methylprednisolone (Solu-Medrol) 2 h before the RAE procedure, followed by 2 days of intravenous prednisolone (Predonine; 2 mg/kg/day), which was tapered by halving the dose every 2 days within the course of 2 weeks. After the discharge, intravenous prednisolone was changed to oral prednisolone (Predonine). PES was defined as the presence of fever, pain, nausea, or vomiting. Data were compared between the steroid and non-steroid groups and between PES and non-PES groups.

Results

The PES incidence rate was 76%, and a comparison between the steroid and non-steroid groups revealed that steroid use significantly decreased the incidence of PES (P < 0.001), including fever (P < 0.001), pain (P = 0.005), and nausea (P = 0.028). The use of anti-inflammatory drugs during the hospital stay was significantly lower in the steroid group (P = 0.019). Moreover, in the steroid group, C-reactive protein level was significantly lower (P = 0.006), whereas white blood cell count was significantly higher (P = 0.004). Conversely, the median length of hospital stay was not significantly shorter in the steroid group (P = 0.292).

Conclusions

The prophylactic use of steroids before and after embolization of renal AML may be effective in preventing PES in this small retrospective study.

Safety, Efficacy, and Predictors for Late Reintervention After Embolization of Renal Angiomyolipomas – Embolization renal angiomyolipoma

Purpose To retrospectively analyze the procedural and long-term clinical outcome of the selective embolization of renal angiomyolipoma. In addition, potential predictive factors for higher risk of late re-intervention were analyzed.

Methods Retrospective monocentric study, including 34 consecutive patients, analyzing the safety, efficiency, and long-term clinical outcome of catheter-directed embolization of renal AML. Additionally, the difference in postembolization renal function between patients embolized in the acute and in the elective setting was analyzed. Secondly, we also evaluated whether volume/diameter of the AML and presence of intralesional aneurysms are risk factors for late re-intervention.

Results Embolization of renal AML was performed to control volume (n = 21; 62 %) or to stop spontaneous hemorrhage (n = 13; 38 %) with angiographic success in all cases but was associated with renal abscess (n = 1) and pulmonary embolism (n = 1) without a significant difference in renal function before and after embolization (P = 0.513). Volume/diameter (P = 0.276/P = 0.21) and presence of aneurysms before embolization (P = 0.37) are not predictive for a higher risk of late re-intervention.

Conclusion Catheter-directed embolization is a safe and effective treatment modality for asymptomatic and bleeding renal AML, without a negative impact on renal function. Initial mass volume/diameter or presence/absence of intralesional aneurysms does not seem to be predictive for late re-intervention.

Key Points:

Citation Format

Selective Arterial Embolization of Renal Angiomyolipomas with a N-Butyl Cyanoacrylate-Lipiodol Mixture: Efficacy, Safety, Short- and Mid-Term Outcomes

Selective arterial embolization (SAE) for renal angiomyolipoma (rAML) is effective to treat or prevent bleeding. We report our experience using a cyanoacrylate–Lipiodol mixture. We performed a single-center retrospective review of all rAMLs embolized with cyanoacrylate glue between July 2014 and June 2020. Demographics, tuberous sclerosis complex (TSC) status, clinical presentation, angiography features, and follow-up data were recorded. Pre- and post-procedure rAML sizes and volumes were estimated from computed tomography (CT) or magnetic resonance imaging (MRI) studies. Kidney function was assessed before and after the procedure. We identified 24 patients (22 females and 2 males, mean age 51 years) treated for 27 AMLs, either prophylactically (n = 20) or as an emergency (n = 4). Technical success was achieved for 25/27 AMLs; two patients, each with a single AML, required nephrectomy and repeated embolization, respectively. Major complications occurred in three patients and minor complications such as postembolization syndrome in 15 patients. AML volume reduction after embolization was 55.1% after a mean follow-up of 15 months (range, 1–72 months). Factors associated with greater volume reduction were a smaller percentage of fat (p = 0.001), larger initial rAML volume (p = 0.014), and longer follow-up (p = 0.0001). The mean creatinine level did not change after SAE. Embolization of rAMLs with a mixture of cyanoacrylate and Lipiodol is feasible, safe, and effective in significantly decreasing tumor volume.

Efficacy and safety of prophylactic superselective embolization for angiomyolipoma at the renal hilum

Objective

This study investigated the efficacy and safety of superselective transcatheter arterial embolization for angiomyolipoma at the renal hilum.

Methods

Between August 2012 and January 2015, 13 patients with 16 angiomyolipomas at the renal hilum underwent initial, prophylactic, superselective transcatheter arterial embolization. The patients were followed by computed tomography or magnetic resonance imaging, and volume-reduction ratios after embolization were measured.

Results

The mean or median post-embolization volume reduction ratios were 23% (follow-up duration, 1–2 months), 55% (3–6 months), 55% (7–12 months), 66% (1–2 years), 67% (2–3 years), and 54% (>3 years). After initial embolization, none of the 16 tumors bled or required surgery; two (13%) tumors recurred; and three (19%) tumors received repeat embolization. Estimated glomerular filtration rates were not decreased at medians of 7 days (near the time of discharge) and 39 days (first clinical follow-up) post-procedure, compared with baseline. Except for post-embolization syndrome, no procedure-related complications occurred.

Conclusions

Superselective embolization for renal hilar angiomyolipoma is safe and kidney-preserving, with good tumor volume reduction and bleeding prevention.

Evidence-based protocol-led management of renal angiomyolipoma: A review of literature

Renal angiomyolipomas (R-AMLs) are rare benign tumors, which occur sporadically and in association with genetic conditions such as tuberous sclerosis complex (TSC) and lymphangioleiomyomatosis (LAM). The key clinical concern is life-threatening hemorrhage. There is uncertainty about the optimal management strategy for patients with R-AMLs. We aim to review the evidence and provide a protocolled approach for the management of R-AMLs. A literature search of R-AML was conducted using MEDLINE and EMBASE for articles published between January 1990 and March 2020. Patient with TSC and sporadic cases were included. Treatment strategies, including active surveillance, surgery, selective arterial embolization (SAE), ablation, and systemic therapies, were reviewed. Outcomes from contemporary case series of active surveillance, surgery, and SAE were collated. There were no randomized controlled trials on this topic. The retrospective case series reviewed showed that many R-AMLs can be managed safely with active surveillance. Tumor size is the most important predictor of bleeding, and other factors such as rate of growth, women of child-bearing age, aneurysm size, and symptoms should be considered when deciding on prophylactic treatment. There is limited evidence for the traditional 4-cm cutoff for treatment, which may lead to overtreatment. The primary intervention options are SAE and surgery; whereas SAE is a less invasive option, nephron sparing surgery offers a lower risk of recurrence. Both appear to have similar morbidity, and the current evidence does not recommend one over the other in most cases. Thermal ablation has promising results but has only been trialed in small case series. Patients with TSC can be offered mammalian target of rapamycin inhibitors of which everolimus appears to cause the greatest shrinkage of tumors with an acceptable side-effect profile. R-AMLs should be assessed for their risk of bleeding. Low-risk tumors should be treated with active surveillance. High-risk tumors should be treated with SAE or surgery. Systemic treatments are the first-line of treatment for patients with TSC to preserve renal parenchyma.

Germline mutation of TSC1 or TSC2 gene in Chinese patients with bilateral renal angiomyolipomas and mutation spectrum of Chinese TSC patients

The germline mutation of the TSC1/2 gene in bilateral renal angiomyolipomas is unclear. Meanwhile, the mutation spectrum of Chinese TSC patients has not been revealed. We recruited 78 patients diagnosed with bilateral renal AMLs. High-throughput sequencing was used to detect any variants in TSC1/2 genes. The results showed that 28.6% of patients diagnosed before 45 were with positive results of TSC1/2 test. The rate decreased to 14.3% for those with onset age over 45. For the 315 previously reported Chinese patients, TSC1 patients were more likely to be affected by nonsense mutations (51.1% vs. 20.7%, p<0.001) and had a significantly higher rate of family history than TSC2 patients (37.8% vs. 19.6%, p=0.0067). Moreover, exon8, 15, and 18 were the hotspot mutation regions for TSC1, and exon 29, 33 and 40 were the most common mutation regions for TSC2. Besides, Chinese TSC patients carried more TSC2 alterations (85.7% vs.76.2%, p<0.001), and were more likely to have a family history than those from TOSCA (22.2% vs. 13.9%, p<0.001). In conclusion, patients affected by bilateral renal AMLs should receive genetic testing of TSC ½ genes and Chinese TSC patients have relatively hotspot mutation regions, which are helpful to genetic counseling and clinical decision making.

Bioengineered in vitro Vascular Models for Applications in Interventional Radiology

The role of endovascular interventions has progressed rapidly over the past several decades. While animal models have long-served as the mainstay for the advancement of this field, the use of in vitro models has become increasingly widely adopted with recent advances in engineering technologies. Here, we review the strategies, mainly including bioprinting and microfabrication, which allow for fabrication of biomimetic vascular models that will potentially serve to supplement the conventional animal models for convenient investigations of endovascular interventions. Besides normal blood vessels, those in diseased states, such as thrombosis, may also be modeled by integrating cues that simulate the microenvironment of vascular disorders. These novel engineering strategies for the development of biomimetic in vitro vascular structures will possibly enable unconventional means of studying complex endovascular intervention problems that are otherwise hard to address using existing models.

Can we predict the existence of extrarenal feeders to renal angiomyolipomas?

OBJECTIVES

To identify factors predicting the presence of extrarenal feeders to renal angiomyolipomas (AMLs) METHODS: This is a retrospective study of 44 patients with 58 renal AMLs embolized in our department. Arteriography obtained during embolization and CT angiography obtained before and after embolization were reviewed to characterize AMLs with and without extrarenal feeders. Tumor characteristics were compared between the two groups. Simple logistic regression and ROC curve analysis were performed. P < 0.05 was considered to be statistically significant.

RESULTS

Of the 58 AMLs reviewed, 29% had extrarenal arteries and 71% did not. AMLs with extrarenal feeders were significantly larger than those without, in terms of volume (median, 368 mL versus 109 mL, p < 0.0002) and the largest diameter (mean, 12.0 cm versus 7.7 cm, p < 0.0001). Patient age, presence of tuberous sclerosis complex or sporadic lymphangioleiomyomatosis, and tumor location did not differ between the groups. The largest diameter and volume had similar predictive values for the presence of extrarenal feeders (AUC, 0.83 versus 0.82, p = 0.673). Extrarenal feeders were present in 0%, 21%, and 79% of the AMLs ≤ 6.5 cm, AMLs 6.6-10.5 cm, and AMLs > 10.5 cm, respectively.

CONCLUSIONS

AML size correlates with the presence of extrarenal feeders, with the largest diameter and volume being significant predictors. AMLs > 10.5 cm had a high chance of extrarenal feeders, making it mandatory to search for feeders to them in order to avoid incomplete embolization; AMLs ≤ 6.5 cm did not have extrarenal feeders, making a search for them unnecessary in these cases.

KEY POINTS

• The presence of extrarenal feeders to renal angiomyolipoma is associated with tumor size, but not with patient age, concomitant disease, or tumor location. • The largest diameter and volume predict the presence of extrarenal feeders to AML, with similar predictive values. • AMLs > 10.5 cm have a high chance (79%) of extrarenal feeders, making it mandatory to search for feeders to them in order to avoid incomplete embolization; AMLs ≤ 6.5 cm do not have extrarenal feeders, making a search for them unnecessary in these cases.