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Friday, October 16, 2020

Evaluation of the Effect of Routine Antibiotic Administration after Uterine Artery Embolization on Infection Rates


Clinical question
What is the effectiveness of routine administration of post-procedure antibiotics after uterine artery embolization (UAE) to prevent procedure-related infections?

Take-away point
No increased rate of infections were seen after UAE for fibroids when post-procedure antibiotics were discontinued.

Reference
Evaluation of the Effect of Routine Antibiotic Administration after Uterine Artery Embolization on Infection Rates. Graif, A. et al. Journal of Vascular and Interventional Radiology, Volume 31, Issue 8, 1263-1269.

Click here for abstract

Study design
Single-center retrospective cohort study

Funding source
No funding

Setting
Private hospital: Christiana Care Health System, Newark, DE




Visual synopsis


Summary


Given the increasing need for antibiotic stewardship and further development of UAE treatment, a single-center retrospective cohort study was performed to address the infection rate following UAE for fibroids when no post-procedure antibiotics were given. In 2018 the SIR last recommended the use of pre-procedure antibiotics for UAE. However, post-procedure antibiotics are not recommended unless there is evidence of possible infection. Despite these recommendations, many patients still receive a post-procedure course of antibiotics. Previous UAE studies acknowledge post-procedure antibiotic use, however no subgroup analyses regarding specific antibiotic usage were performed. In the HOPEFUL study (Hysterectomy Or Percutaneous Embolisation For Uterine Leiomyoma), it showed benefit from expected general side effects after the procedure, but no overall effect in the rate of infections. Therefore, this study aims to address the effectiveness of routine administration of post-procedure antibiotics after UAE in the prevention of procedure-related infection.

At this private institution prior to 2016, patients who received routine pre and post procedure antibiotics (n=217) were compared to those after 2016, where no post-procedure antibiotics (n=158) were given. Pre-procedure antibiotics for the no-antibiotics group consisted of weight based dose of IV cefazolin, whereas the post-procedure antibiotics group received IV 500mg ciprofloxacin. Post-procedure antibiotics were oral ciprofloxacin 500mg twice daily for five days. These two groups were compared for infectious complications with primary endpoints being an infectious complication requiring therapy with antibiotics, re-admission or surgical intervention within three months. Infections were subsequently classified as minor or major. The secondary endpoint was 90-day mortality. Demographics were similar between the two groups, though the no-antibiotics group had a significantly higher rate of diabetes and a lower rate of adenomyosis. The procedure was similar in each group with regards to arteries embolized, number of vials used and procedural steps. However, in the antibiotics group patients received only embospheres, whereas in the no post-procedure antibiotics group patients received embospheres, embozene or both.

No statistically significant difference was seen between the number of infections (P=.66) when comparing the post-procedure antibiotics group (4/217, 1.8%) to the no-antibiotics group (2/158, 1.3%). Overall infection rate was (6/375, 1.6%), occurring at a median of 15.5 days. Overall minor complications (3/375, 0.8%) did not differ between the groups. The primary symptom was malodorous vaginal discharge, requiring empiric oral antibiotic therapy. Overall major complication rates also did not differ between the groups (3/375, 0.8%). Major infectious complications resulted in two patients who underwent hysterectomy and one patient receiving a myomectomy. No 90-day mortalities were seen. Regardless of antibiotic usage, infectious rates and complications found in this study mirror previous large retrospective studies and meta-analyses. The authors conclude that post-procedure antibiotic prophylaxis after UAE did not result in increased rates of minor or major infectious complications.

Commentary


This study helps underscore the current SIR antibiotic recommendations and encourages practitioners to use post-procedure antibiotic prophylaxis cautiously. Previous studies lacked the clarity behind specific antibiotic usage and regimens that this study addresses. However, there are a few aspects to this paper regarding power, type of study, and the differences between the two groups that should be considered.

This study lacks power given its smaller sample size and generalizability due to its single-center retrospective nature. Due to the lack of power, they were not able to perform regression analyses based on types of particles used and characterization of fibroid disease, both of which may play a role in procedure related infections. Reassuringly, this study has similar infectious rates when compared to previous large prospective studies. Differences between the two groups that should be considered are differing pre-procedure antibiotic regimen, variation of embolization particles and their loss to follow up rate. Though complications were low and similar to previous studies, overall 50% of complications were minor and 50% were major. The main minor complication noted was malodorous discharge. This may also be underreported or not fully captured given the 13.4% of those lost to follow up. Overall, this is an important study that guides the decision on whether or not to prescribe post-procedure antibiotic prophylaxis in UAE.

Post Author
Marissa Stumbras, MD
Interventional Radiology Resident, PGY2
Oregon Health & Science University

@MarissaStumbras

Monday, October 12, 2020

Cost Effectiveness of External Beam Radiation Therapy Versus Percutaneous Image-guided Cryoablation for Palliation of Uncomplicated Bone Metastases


Clinical question
Is percutaneous image-guided cryoablation a cost effective method for pain palliation in uncomplicated bone metastatic lesions? How does it compare to external beam radiation and in what combination?

Take-away point
Cryoablation is not cost effective for palliation of uncomplicated bone metastases in the initial setting. However, cryoablation is a potentially cost effective alternative for recurrent pain palliation following external beam radiation therapy.

Reference
Cost effectiveness of external beam radiation therapy versus percutaneous image-guided cryoablation for palliation of uncomplicated bone metastases. Chang, E.M., Shaverdian, N., Capiro, N., Steinberg, M.L., Raldow, A.C. Journal of Vascular and Interventional Radiology (JVIR), Volume 31, Issue 8, 1221-1232.

Study design
Cost effectiveness analysis using a Markov model with 1-month cycles over a lifetime horizon, 2017 Medicare outpatient setting reimbursement as cost estimate, and $100,000 per quality-adjusted life-year as willingness-to-pay threshold. Strategies evaluated included external beam radiation therapy (RT) in single fraction (SF) followed by SFRT, SFRT-ablation, ablation-SFRT, multiple-fraction radiation therapy (MFRT) followed by MFRT, MRFT-ablation, and ablation-MFRT.

Funding source
No funding source was disclosed.

Setting
Academic hospital. University of California Los Angeles, Los Angeles, California.







Figure. Visual synopsis.

Summary


Metastatic lesions to the bone, which is the third most common site of metastatic disease after lung and liver, carry significant morbidities, as 50% of patients would develop poorly controlled pain. Radiation therapy (RT) is a well-established treatment however onset of pain relief may take up to 6 weeks. Percutaneous image-guided cryoablation may be a good alternative given its rapid onset of pain relief but it carries an associated procedural cost. Therefore, a cost-effectiveness analysis is needed to assess the optimal utilization of cryoablation in combination with radiation therapy, whether it be single fraction (SFRT) or multiple fraction radiation therapy (MFRT).

The authors performed a cost effectiveness analysis using a Markov model with 1-month cycles over a lifetime horizon, 9 months as median overall survival, outcome probabilities extracted from medical literature, 2017 Medicare outpatient setting reimbursement and 2016 Agency for Healthcare Research and Quality data as cost estimate, $100,000 per quality-adjusted life-year as willingness-to-pay threshold, and 1 million simulated patients. Strategies evaluated included external beam radiation therapy (RT) in single fraction (SF) followed by SFRT, SFRT-ablation, ablation-SFRT, multiple-fraction radiation therapy (MFRT) followed by MFRT, MRFT-ablation, and ablation-MFRT. SFRT was defined as 8 Gy in 1 fraction. MFRT was defined as 30 Gy in 10 fractions. Ablation-ablation was not included as a treatment strategy given very limited evidence of outcomes following repeated cryoablations.

Using RT-RT as a baseline (SFRT and MFRT for their respective comparisons), RT-ablation was found to be cost effective but not ablation-RT. Tornado analysis, specifically for comparison between SFRT-SFRT and SFRT-ablation demonstrated that the results were most sensitive to probability of return of pain and probability of pain relief after cryoablation. Other important variable dependency included median overall survival. RT-RT remain the most cost-effective for median survival <= 8.7 months for SFRT and <= 7.9 months for MFRT. Ablation-RT became more cost-effective for median survival >= 196.4 months for SFRT and >= 19.8 months for MFRT. RT-ablation was the most cost-effective for median survival in between the above mentioned intervals.

Commentary


The authors in this paper have evaluated in details the cost-effectiveness of percutaneous image-guided cryoablation in the setting of uncomplicated bone metastatic lesions for pain palliation in combination with radiation therapy. With a current median overall survival of 9 months, radiation therapy followed by ablation is the most cost-effective. This information is important for referring clinicians and patient advocates. As the authors have also noted, the analyses were highly sensitive to effectiveness of cryoablation as well as median overall survival. A stratified clinical pathway may be proposed with patients with poor prognosis undergoing radiation therapy followed by radiation therapy while patients with longer expected survival may benefit from ablation followed by radiation therapy with regards to cost-effectiveness. More data from prospective trials, particularly on the pain relief/recurrence rate after cryoablation, as well as ongoing economic and clinical assessment will be needed to further delineate the optimal treatment pathway and modality choice. Clinical decisions in other treatment pathways may benefit from rigorous cost-effectiveness analyses such as this paper presented by the authors.

Post Author
Ningcheng (Peter) Li, MD, MS
Integrated Interventional Radiology Resident, PGY-4
Department of Interventional Radiology
Oregon Health and Science University, Dotter Interventional Institute 

@NingchengLi

Friday, October 9, 2020

Evaluation of Fibrinogen Levels during Catheter-Directed Thrombolysis for Acute Pulmonary Embolism


Clinical question
How are plasma fibrinogen level (PFL) affected by catheter-directed thrombolysis (CDT) in the setting of acute pulmonary embolism (PE) and is PFL associated with hemorrhagic complications in this setting?

Take-away point
CDT significantly decreases PFL, but is not associated with hemorrhagic complications.

Reference
Graif A, Grilli CJ, Kimbiris G, Paik HH, Leung DA. Evaluation of Fibrinogen Levels during Catheter-Directed Thrombolysis for Acute Pulmonary Embolism. J Vasc Interv Radiol. 2020;31(8):1281-1289. doi:10.1016/j.jvir.2020.04.032

Click here for abstract

Study design
Retrospective, single-institution cohort study of 147 patients undergoing CDT for acute massive and submassive PE.

Funding source
No reported funding 

Setting
Private hospital network, Christiana Care Health System, USA.






Figure. Visual synopsis summarizing of study design and main results.


Summary


Catheter-directed thrombolysis (CDT) with tissue plasminogen activator (tPA) for acuate pulmonary embolism (PE) is thought to mitigate, although not eliminate, hemorrhagic risk compared to systemic thrombolysis. Some clinicians monitor plasma fibrinogen level (PFL) to anticipate hemorrhage, but supportive evidence is lacking. The authors performed a retrospective study of 147 cases of CDT for acute PE and evaluated PFL and its relationship with hemorrhagic complications.

Patients included in the study were adults presenting with acute massive or submassive PE who received either conventional catheter-directed thrombolysis (CCDT) or ultrasound-accelerated thrombolysis (USAT). Patients were excluded if presenting symptoms were >14 days, chronic PE was evident on CTA, or systemic tPA had been given prior to CDT. All patients received systemic anticoagulation with either unfractionated heparin (UFH) or low molecular weight heparin (LMWH).

Primary endpoints included change in initial and final PFL (with subgroup analyses of CCDT vs USAT and UFH vs LMWH groups) and PFL nadir. Secondary endpoints included correlation between PE severity metrics with PFL as well as tPA infusion rate, duration, and total dose.

A total of 147 cases met criteria with 98 undergoing CCDT, 34 undergoing USAT, and 15 undergoing a combination of both (excluded from CCDT vs USAT subgroup analysis). Anticoagulation was achieved with UFH in 102 cases and LMWH in 45 cases. Primary results showed a significant mean decrease from initial PFL to final PFL (-15.1 ± 69.4 mg/dl, p=0.007) and a PFL nadir of 327.6 ± 107.1 mg/dl.

Subgroup analyses did not reveal a significant difference in initial or final PFL between patients receiving UFH or LMWH; although, PFL nadir was significantly lower in the UFH group (313.7 ± 97.4 mg/dl, p= 0.03). No significant difference in initial, final or nadir PFL levels was detected between CCDT and USAT groups. In the CCDT group, there was a significant decrease in initial and final PFL (-14.9 ± 60.9 mg/dl, p=0.01) compared to the USAT group, which showed a nonsignificant increase in initial and final PFL. Secondary endpoint results showed no significant correlation between PE severity indices and any PFL or infusion metrics.

Six hemorrhagic complications were observed with no significant difference in change in PFL or between final PFL, PFL nadir, or change in PFL compared to cases without hemorrhagic complication.

The authors discuss that although there was a significant decrease in PFL during CDT for acute PE, this did not translate to clinical significance as PFL did not reach commonly used thresholds for modification or discontinuation of CDT. Two other, smaller studies evaluating PFL during CDT found similar decreases in PFL, although did not evaluate hemorrhagic complications. One study found a moderate positive correlation between PFL nadir and PE severity, which conflicts with the nonsignificant results from the current study.

Commentary


The authors evaluate PFL in a relatively large cohort of patients undergoing CDT. The larger sample size compared to previously published studies offers increased confidence in the main conclusion that PFL is significantly decreased in this population. However, they discuss that their study was insufficiently powered to evaluate the relationship between PFL and hemorrhagic complications given the very small number of total hemorrhagic complications (n=6). Additionally, the retrospective nature of this study inherently introduces inconsistencies and confounds, which can be amplified in the smaller subgroup analyses. Despite a significant primary endpoint, more data are needed to fully explore the relationship between PFL and hemorrhagic complications in this subgroup of patients receiving CDT for acute PE before any changes to clinical management can be made confidently.

Post Author
Catherine (Rin) Panick, MD
Resident Physician, Integrated Interventional Radiology
Dotter Interventional Institute
Oregon Health & Science University

@MdPanick

Monday, October 5, 2020

Predictors of Progression-Free Survival and Local Tumor Control after Percutaneous Thermal Ablation of Oligometastatic Breast Cancer: A Retrospective Study


Clinical question
What predicts local progression and progression-free survival following ablation of oligometastatic disease in breast cancer?

Take-away point
Thermal ablation can locally eliminate tumor progression for pulmonary, hepatic, bone and soft tissue oligometastatic disease in breast cancer if margins are greater than 5 mm.

Reference
Ridouani F et al. Predictors of Progression-Free Survival and Local Tumor Control after Percutaneous Thermal Ablation of Oligometastatic Breast Cancer: A Retrospective Study. Journal of Vascular and Interventional Radiology. July, 2020.

Study design
Retrospective Review

Funding source
Self-funded or unfunded

Setting
Single Institution






Figure 2. (Left column) Kalpan-Meier analysis demonstrates PFS from the time of initial ablation for all patients (top), for eradication of disease vs control of disease groups (P = .05) (second row), ER-positive compared to ER-negative patients (P= .037) (third row), and by minimal ablation margin of 5 mm (P= .33). (Right column) Kaplan-Meier analysis shows TTP from initial ablation for all patients (top row), for eradication of disease vs control of disease groups (P =.29), ER-positive compared to ER-negative patients (P= .08) (third row), and by minimal ablation margin of 5 mm (P= .036) (bottom row). The x-axes are months, and the y-axes are proportion at risk. ER-receptor status and age ≤ 60 years old demonstrated significant improved PFS. Additionally, ablation margin ≥ 5 mm showed longer median TTP (13 versus 5 months). Adverse events were noted to be moderate in 8% of liver ablations and 28% in lung ablations. 

Summary


Utilizing a single-center, retrospective database search, the authors identified 33 patients (46 ablations) with 5 or fewer enlarging or increasingly metabolically active breast cancer metastatic lesions who underwent thermal ablation to the lung, liver, bone, or soft tissues. Radiofrequency ablation, microwave ablation, or cryoablation was performed with computed tomography, positron-emission tomography, or magnetic resonance image guidance. 35 liver (76%), 7 lung (15%), and 4 soft tissue or bone (8%) metastases were treated. 78% of patients were estrogen receptor positive, 51% progesterone receptor positive, 27% human epidermal growth factor receptor (HER2) positive, and 9% were triple negative. The median time from metastatic diagnosis wot ablation was 39 months. All patients received systemic chemotherapy, hormone therapy, or targeted therapy. Additionally, some patients also had surgical, radiation, or trans-arterial treatment.

91% of the procedures had technical success defined as no residual disease on initial post-procedure imaging. Local tumor progression was noted in 5 patients (15%) at 4-9 months following ablation. Ablation margins were measured in 83% of ablations with median margin being 6 mm. Median overall survival from first ablation treatment was 70 months with 1, 3, and 5 year survivals of 96%, 72%, and 55%. Median progression free survival was 10 months with median time to progression of 11 months.

Commentary


With breast cancer being so common and greater than a quarter of these patients developing metastatic disease, this creates a large population of patients necessitating treatment. Studies have suggested that local treatment of breast cancer metastases may improve survival. This study added to this growing body of literature. Unsurprisingly, results were best in younger patients and larger margins. However, greater performance free survival was also seen in ER-positive patients.

Percutaneous ablation is clearly feasible and in appropriately selected patients have comparable results to surgery. Additionally, eradication of all disease can allow patients to take holidays from their systemic therapies.

Limitations include a small sample size, especially when considering four sites of disease and three ablation modalities. Additionally, image guidance used in this study, including PET/CT and MR guidance, is not widely available. However, clearly ablation should be included in the treatment paradigm who would benefit from treatment of their oligometastatic disease and tumor boards should consider this therapy in addition to surgery, radiation, and trans-arterial treatments.

Post Author:
David M Mauro, MD
Assistant Professor
Department of Radiology
Vascular and Interventional Radiology
University of North Carolina

@DavidMauroMD

Friday, October 2, 2020

Intermediate to Long-Term Clinical Outcomes of Percutaneous Cryoablation for Renal Masses


Clinical question
What is the intermediate- and long-term efficacy and safety of percutaneous cryoablation (CA) in the treatment of renal masses?

Take-away point
CA is effective in treating renal masses with low rates of complications during the procedure and over intermediate- and long-term follow-up periods.

Reference
Knox J, Kohlbrenner R, Kolli K, et al. Intermediate to Long-Term Clinical Outcomes of Percutaneous Cryoablation for Renal Masses. J Vasc Interv Radiol. 2020;31(8):1242-1248.

Click here for abstract

Study design
Retrospective cohort study

Funding source
Self-funded or unfunded

Setting
Single institution, University of California San Francisco








Figure. Graph of overall survival (OS) Kaplan-Meier curve in patients with RCC

Summary


Procedural treatment of renal masses has classically been accomplished using partial or total nephrectomy. While newer percutaneous cryoablation (CA) and thermal ablation techniques have been shown to be safe and effective compared to surgery for T1 disease, there is a paucity of data on their intermediate- and long-term safety and efficacy.

In this study, the investigators sought to assess the intermediate- and long-term safety and efficacy of percutaneous CA for renal masses at a single institution. Patients who had undergone ablation with percutaneous CA for T1a or b renal masses were selected. Patients with multiple masses, history of prior nephrectomy, and inherited tumor syndromes were included. Outcomes included renal function pre- and post-procedure, intra- and post-procedure complications, local recurrence, new metastatic disease, or complete response. R.E.N.A.L. nephrectomy score, a metric evaluating renal mass complexity that was previously validated as a measure of 30-day nephrectomy morbidity, was also calculated for each renal cell carcinoma (RCC) mass.

277 patients, 297 renal masses, and 299 CA procedures were analyzed. 207 masses were <3 cm, 74 were between 3 and 4 cm, and 16 were greater than 4 cm. 22 patients underwent multiple ablations; 12 due to separate mass, 7 due to incomplete initial ablation, and 3 due to recurrence. 46 patients had a history of prior renal surgery before CA. 4 patients had a known underlying genetic disease associated with their renal masses. 234 masses were confirmed RCC, 40 had nondiagnostic biopsies, and 8 had no biopsy results. 15 were biopsied at time of CA but were later found to be benign. Of the 234 RCC tumors, there were 93 (39.7%), 114 (50.8%), and 27 (11.5%) low-, intermediate-, and high-nephrectomy scoring masses respectively. There was no significant difference between pre-and 1-day post-procedural eGFR, but eGFR declined an average of 2.4 mL/min/1.73 m2 from preprocedural values to 3-month follow-up. There was no difference in decline between patients with and without prior renal surgeries or between patients with or without history of contralateral nephrectomy.

12 major complications occurred in 9 procedures (3%) with none resulting in death or permanent disability. AKI requiring hospitalization occurred 5 times, with none of the patients requiring hemodialysis. One patient suffered a retroperitoneal hematoma requiring transfusion and one patient had a renal artery pseudoaneurysm treated with embolization. Additionally, single occurrences of hemothorax, NSTEMI, post-procedural pulmonary embolism, high fever, and traumatic bladder catheter placement were all noted. Major complications occurred at a higher mean age (73.1) compared to uncomplicated procedures (65.6) (p=0.03). Tumor characteristics and high nephrectomy score did not affect complication rate (p=0.97) but significantly more complications occurred in patients with history of prior renal surgery (p<0.05).

For the 199 patients with RCC masses and follow-up information, mean clinical and imaging follow-up length was 29.7 months and 27.4 months respectively. Complete response was achieved in 195 masses (95.6%) after one procedure and 200 (98%) after 2 procedures. Mean time to complete response was 4.2 months. Local recurrence was noted in 3 cases (1.5%). Mean time to recurrence was 42.9 months (19.9-76.9 mo.). There was no association between recurrence and specific RCC mass characteristics. Recurrence did occur more often in patients with history of prior renal surgery (p=0.03). 10 patients developed metastatic disease (5.2%) at a mean follow-up time of 38.3 months. Independent factors associated with metastatic progression or local recurrence included history of prior kidney surgery, increased mass size, and clear cell subtype.

Commentary


In this cohort, CA was demonstrated to be a safe and effective treatment modality for patients with renal masses. It offered high response rates with low recurrence and metastatic progression, and had lower complication rates than previous partial nephrectomy studies. Noted decreases in eGFR at 3-month follow-up were unlikely clinically significant and were less than those reported for partial nephrectomy. Patients with prior kidney surgery were at higher risk of complications, local recurrence, or metastatic disease, consistent with prior studies. Additionally, patients who experienced metastatic progression had aggressive disease features, bilateral disease, or did not have complete response after their first ablation. This study is limited by its retrospective nature and single arm design. Future studies will prospectively compare partial nephrectomy and CA procedures over extended follow-up periods.


Post Author
Jared Edwards, MD
General Surgery Intern (PGY-1)
Department of General Surgery
Naval Medical Center San Diego, San Diego, CA

@JaredRayEdwards



Friday, September 11, 2020

Venous Biomechanics of Angioplasty and Stent Placement: Implications of the Poisson Effect


Clinical question
Characterize the poisson effect following venous angioplasty and stents placement in veins.

Take-away point
There is a proportional longitudinal foreshortening and narrowing of adjacent venous segments with radial expansion of venous angioplasty and stents, which is more dramatic in veins than arteries.

Reference
Li N., Mendoza F., Rugonyi S., Farsad K., Kaufman J.A., Jahangiri Y., et al. Venous Biomechanics of Angioplasty and Stent Placement: Implications of the Poisson Effect. J Vasc Interv Radiol. 2020 Aug; 31 (8): 1348-1356.

Click here for abstract

Study design
Prospective in Vivo swine model Testing with Real-Time Venous Wall Motion Monitoring and finite-element computational vascular model analysis

Funding source
No reported funding

Setting
Academic setting. Oregon Health and Science University, Portland, Oregon, USA







Figure
A visual synopsis of the 2 study parts and summary of results.

Summary


Venous angioplasty and stent placement for treating venous outflow obstruction has demonstrated improved flow with clinical symptom relief. However, adjacent segment narrowing after stent placement, based on the poisson effect, may carry a negative impact on the quality of venous flow. Research on venous biomechanics for venous-specific stent designs is lacking. The author performed a prospective 3 adult swine in vivo testing with real-time venous wall motion monitoring and finite-element computational vascular model analysis to characterize the poisson effect during angioplasty and stent placement. Statistical analysis including Welch t test, analysis of variance, Pearson correlation, linear regression, and polynomial curve fit were performed using Prism software.

1- Real-Time Venous Wall Motion Monitoring:

Study veins were accessed and baseline venography was obtained followed by RF ablation induced stenosis and repeat venography. Balloon angioplasty, with diameter matching the naive vein(8mm), was performed on the in the stenotic regions of one side. Bare metal stents oversized by 50% (12mm) were deployed in the contralateral stenotic region. Iron particles were injected on the venous endothelium proximal to the intended vessel segment and categorized into near group (mid-point to balloon) and far group (peripheral to angioplasty area). Neodymium magnet was placed externally for iron attraction allowing real-time visualization of the vessel wall under fluoroscopy.

· During balloon angioplasty, the mean venous stenosis decreased by 43.7% ± 2.1. There was significant longitudinal displacement of the iron particles toward the balloon midpoint(1.5% ± 0.2 of the balloon length P <.001) affecting the far group more (2.2%) compared to near group (0.9%)(t test, P< .001). The adjacent luminal collapse correlated with diameter increase of the angioplasty-treated segment (relative collapse % . 0.772 * [relative dilatation %] . 0.255; R2 . 0.8920.

· During bare metal stent deployment the mean venous stenosis reduced to 20.8% ± 0.8, with further reduction to 1.6% ± 1.2 with balloon angioplasty of the stent. There was significant longitudinal displacement toward the midpoint of the balloon(2.0% ± 0.5 of the balloon length P< .01). The longitudinal displacement increased with distance to the midpoint of the balloon in a direct linear relationship (R2 . 0.87).

2- Finite-Element Computational Vascular Model (using ADINA software)

Several parameters were obtained from the literature to simulate a healthy common iliac vein and artery. During angioplasty simulation, the reduction of the adjacent-segment diameter had a significant correlation to the degree of dilation of the treated segment. Angioplasty simulation using arterial wall biomechanical properties showed significantly less adjacent segment narrowing compared with the model using venous properties. Variations of Young moduli in the longitudinal direction had a positive relationship with the amount of adjacent segment collapse, while with circumferential direction had the opposite effect and with the radial direction had no significant impact.

The findings explain the decrease of external iliac vein diameter after stent placement in the common iliac vein. Such phenomenon is due to the nonlinear elastic property of veins secondary to the nonaligned collagen fibers in the predominant adventitia. In contrast, arteries have coaligned collagen fibers in the dominant media layer. Previous and current study showed that veins are more extensible in the circumferential direction than in the longitudinal direction since they have a much higher longitudinal young modulus and a higher longitudinal vs circumferential Poisson ratio (opposite to arteries). With radial outward force applied to venous segments, there is a significant redistribution of forces and venous tissue, resulting in a pronounced Poisson effect.

Commentary


The authors in this study captured an important consequence of venous angioplasty and stent placement. They characterized its dramatic Poisson effect in veins and showed the resulting longitudinal foreshortening and adjacent segment collapse. Although the study has limitations including the small sample size, the possible collagen contraction after RF ablation and the lack of survival period to examine chronic changes. The study can still provide innovative solutions on vein-specific flow optimization. Current stent designs place heavy emphases on maximizing radial resistive force and chronic outward force, which may be counterproductive in venous interventions. Therefore applying and examining this study phenomenon on novel innovative venous stents, with emphasis on overcoming force and tissue redistribution related to the Poisson effect, might maximize venous flow leading to better patient outcomes.

Post Author
Tarig Elhakim, MD
PGY-2 Internal Medicine Residency,
Kendall Regional Medical Center


@TarigElhakim

Monday, September 7, 2020

Ablation Therapy for Advanced Stage Non-Small Cell Lung Cancer: A National Cancer Database Study


Clinical question: 

In patients with clinical stage IIIB or stage IV non-small cell lung cancer (NSCLC), is overall survival (OS) prolonged in patients who undergo ablation therapy (AT) compared to patients who do not receive AT?

Take away point: 

In patients with advanced stage NSCLC, AT as the sole therapy other than chemotherapy may be associated with prolonged overall survival.

Reference: 

Halsey, Kasey et al. (2020). “Ablation Therapy for Advanced Stage Non-Small Cell Lung Cancer: A National Cancer Database Study.” Journal of Vascular and Interventional Radiology 31 (8): 1210-1215.

Click here for abstract

Study design: 

Retrospective review

Funding source: 

National Natural Science Foundation of China grant

Setting: 

Multi-center, at cancer-accredited medical centers, utilizing the National Cancer Database (NCDB).





Summary:

Ablative Therapy (AT) is progressively utilized in the treatment of inoperable and early-stage NSCLC due to well-demonstrated prolonged survival rates, however little data exists on the efficacy AT in the treatment of late-stage NSCLC. Here, the authors retrospectively reviewed overall survival among patients with stage IIIB or stage IV NSCLC who were treated with AT as the only treatment aside from chemotherapy compared to patients who did not undergo AT.

Patients who underwent any other treatment modality for NSCLC were excluded. This resulted in a total of 140,819 patients (mean age of 69 years, 54.7% male) that were included in the study, of which 249 received AT. OS between these two cohorts was then calculated from the time of diagnosis to the time of death.

The median OS for all included patients was 5.0 months. Using a multivariate cox regression the cohort receiving AT had longer OS, however this was not a statistically significant difference. Propensity matching based on demographic and clinicopathologic characteristics was performed which resulted in a statistically significant OS of 5.9 months in the AT group compared to 4.7 months in the control group.

Additional propensity matching for tumors less than or equal to 3 cm resulting in statistically significant OS of 14.0 months in the AT group compared to 4.7 months in the control group.

Commentary:

Results of this retrospective review with propensity matched groups suggests that AT prolongs OS in patients with stage IIIB or IV NSCLC compared to AT, especially when pre-treatment tumor size is 3 cm or less.

As the efficacy of AT in early stage NSCLC is well-established (2-year survival rates exceeding 90%), this important data also suggests that AT is efficacious in more advanced stages of NSCLC. Importantly, AT can offer a treatment option for patients with late stage NSCLC especially in those who are poor surgical candidate or for those whom palliative care is indicated. The increase in OS in patients who underwent AT with tumor sizes of 3 cm or less is consistent with existing literature supporting excellent outcomes in smaller NSCL tumor sizes.

Limitations in the data presented here include relatively small AT cohort size compared to total included patient size, lack of details of cause-specific mortality, possibility for selection bias in that those who received AT in the setting of advanced stage NSCLC may be patients more clinically favorable for the procedure, and lack of detail regarding the specific ablation techniques performed.


Post Author:
Demetrios Geanon
MD Candidate, Class of 2021
Rush University Medical Center

David M. Tabriz, MD
Assistant Professor
Rush University Medical Center

@DrDaveTabriz