Percutaneous MR Imaging-Guided Laser Ablation and Cryoablation for the Treatment of Pediatric and Adult Symptomatic Peripheral Soft Tissue Vascular Anomalies

Clinical question
Is magnetic resonance (MR) imaging-guided laser ablation, cryoablation safe and effective in treating symptomatic soft tissue vascular anomalies (VAs) in the trunk and extremities?

Take-away point
MR imaging-guided laser ablation and cryoablation are both safe and effective in treating symptomatic soft tissue VAs in the trunk and extremities.

Reference
Augustine MR, Thompson SM, Powell GM, et al. Percutaneous MR imaging-guided laser ablation and cryoablation for the treatment of pediatric and adult symptomatic peripheral soft tissue vascular anomalies. Journal of Vascular and Interventional Radiology. 2021;32(10):1417-1424.

Click here for abstract

Study design
Retrospective cohort study

Funding source
Self-funded or unfunded

Setting
Single institution, Mayo Clinic Rochester, MN

Figure

Figure 1. Magnetic resonance (MR) imaging-guided laser ablation in an 8-year-old female patient with persistent pain from a right lateral thigh intramuscular slow flow venous malformation after multiple prior percutaneous sclerotherapy treatments. (a) The T2-weighted preablation MR image showed a hyperintense intramuscular slow flow venous malformation in the right lateral thigh (yellow arrow). (b) Intraprocedural T2-weighted MR imaging showed the laser fiber (yellow arrow) traversing the venous malformation. The venous malformation was ablated with multiple pullback activations of the laser fiber. After ablation, (c) the T2-weighted and (d) T1-weighted gadolinium-enhanced images showed a decreased T2 signal and enhancement throughout the venous malformation (yellow arrows).

Summary

Soft tissue vascular anomalies (VAs), also referred to as vascular tumors, can result in significant symptomatology whether benign or malignant, simple or combined. These symptoms can be localized, such as pain and cosmetic issues, as well as systemic and life-threatening such as high-output heart failure or consumptive coagulopathy. These masses have classically been treated with surgical resection, percutaneous sclerotherapy, or transarterial embolization depending on characteristics such as size, location, proximity to critical structures, and flow. These modalities often have variable success, requiring multiple treatments to attain remission. Percutaneous ablation procedures, including radiofrequency (RF), cryoablation, and laser ablation, have been demonstrated to be safe and effective in treating the more refractory VAs. However, the most-commonly employed imaging modalities, ultrasound and computed tomography (CT), are limited in their abilities to visualize vascular lesions. Magnetic resonance (MR) imaging is a promising alternative given its unmatched ability in delineating soft-tissue boundaries and its demonstrated ability to effectively monitor treatment response in VAs.

In this retrospective case series, patients with symptomatic VAs treated with MR-guided laser ablation or cryoablation over an approximately 6-year period were analyzed. Patients were included if they had persistently and locally symptomatic VAs after previous first-line therapies, were not offered further first-line therapies, and had lesions in locations that were deemed safe for ablation procedures. All patients underwent pre-procedural MRI and had their pain assessed on the visual analog scale (VAS). Post-procedurally, patients followed up 6-12 months later to have their pain reassessed. This was done via VAS, and patients were classified as either having complete, partial, or no resolution of symptoms. Post-ablation MRI was only obtained if patients had residual symptoms, which occurred in 17 patients. Pre- and post-ablation MR images were compared in terms of maximum VA diameter of the T2 hyperintense portion, semiquantitative percentage enhancement of the total VA at baseline, and the percentage decrease in the T2 signal and enhancement at follow-up. Major and minor complications were also analyzed.

30 patients with 34 VAs treated over 60 sessions were included in this study. The VAs were located in the thorax (n = 3), abdomen/pelvis (n = 2), upper arm (n = 5), forearm (n = 1), hand (n = 1), thigh/hip (n = 12), and lower leg (n = 10). 31 VAs in 27 of the patients caused moderate to severe pain and 3 VAs in 3 patients caused swelling/mass effect, prompting treatment. Mean baseline pain score in painful VAs was 6.4 ± 1.6. 9 patients were taking analgesics to manage this pain, including 2 taking narcotics, 2 taking both narcotic and non-narcotic medications, and 4 patients taking neuromodulatory medications. All 34 VAs were classified as low-flow malformations. Of the 60 ablation procedures, 49 were done with laser, 10 with cryoablation, and 1 with both. The median number of ablations per VA was 1.5 (1-7). 27 ablations utilized both US and MR guidance while 33 used MR alone. Laser ablation was the default modality choice while cryoablation was used in cases in cases with nearby critical structures. 18 sessions resulted in same-day discharge, 36 resulted in overnight observation, and 6 were admitted for greater than 24 hours. All 6 admissions were for post-ablation pain control. Only 23 patients with 27 VAs had adequate follow-up data. At a mean of 12.2 months ± 10.1 (0.4-29.3), 19 (95%) of patients treated for pain and 2 (67%) of patients treated for swelling/mass effect reported partial or complete resolution of symptoms. Mean pain score was 1.6 ± 1.8 (0-5) with a mean reduction of 5.7 ± 1.0 (p < 0.001). 17 patients underwent post-ablation MRI. 15 of these were with contrast. Reduction in maximum size from baseline was 2.3 cm ± 2.7 (p = 0.004). 13 patients experienced >50% decrease VA T2 signal while 11 patients experienced >50% decrease in VA contrast enhancement. No major complications were noted. 10 minor complications occurred in 9 (30%) of the patients. These included post-ablation hematoma (n = 3), transient paresthesia (n = 4), transient weakness (n = 2), and nontarget thermal injury (n = 1).

Commentary

This study builds off of smaller studies of its kind and reports promising outcomes in a larger patient population. MR imaging-guided laser and cryoablation are shown to be safe and effective modalities for treating symptomatic peripheral VAs, both as initial and subsequent therapy for persistent lesions. MR guidance specifically helps to visualize and treat VAs that were not conspicuous on US or CT imaging. Patients suffering from painful lesions in particular experienced significant decreases or resolution in pain post-procedurally. All complications were minor and were treated with minimal observation or short-term hospitalization. 

This study has several limitations, including its retrospective nature, difficulty in accurately measuring VA dimensions post-ablation, and lack of consistent pre-procedure workup and post-procedure follow-up. Also, the use of subjective pain scores is subjective and highly variable. Lastly, the included number of patients/ablations was inadequate to allow detailed assessment of the differences between cryo-ablation versus laser ablation, nor location-specific VA response. Future studies would benefit from symptom reporting standardization, prospective randomized design, and larger patient population.

Post Author
Jared Edwards, MD
General Medical Officer
Medical Readiness Division
Naval Surface Forces Pacific, San Diego, CA
@JaredRayEdwards

Edited and formatted by @NingchengLi

Interventional Radiology Resident

Dotter Institute, Oregon Health and Science University