RU2780366C1 - Method for postoperative evaluation of cryoablation zone in treatment of renal cancer - Google Patents

Abstract

FIELD: medicine.

SUBSTANCE: invention relates to medicine, namely to ultrasound diagnostics, and can be used for postoperative assessment of the cryoablation zone in the treatment of kidney cancer. An ultrasound examination (ultrasound) is performed with an assessment of the shape, structure, contour, echogenicity, and the presence of blood flow. Additionally, ultrasound with echocontrast (ECU) is performed in the area of ​​cryoablation for 1-2 days, then repeated after 3, 6 months and after a year. Ultrasonic contrast agent (UCA) is injected in a volume of 1.5-2.0 ml. The patient is asked to hold his breath at the moment the drug appears in the cortical substance of the kidney and at the time it begins to be washed out of the kidney. To assess the zone of cryoablation, 5 perfusion contrast patterns are used. The pattern of reactive changes is a rounded zone or an irregularly shaped zone with an area of ​​peripheral edema, characterized by the flow of a contrast agent, and an area of ​​central necrosis. The residual tumor pattern is a zone with pronounced asymmetry, residual parietal formation and a zone of necrosis. The pattern of the necrosis zone is a rounded zone in the form of an anechoic avascular area with no contrast agent entering the structure of the ablation zone, has clear contours and a homogeneous structure. The pattern of fibrotic changes is a zone with the presence of fibrous septa without accumulation of a contrast agent with a possible background accumulation in the structure of the septa. The recurrence pattern is a zone with the presence of a nodular formation, characterized by an earlier inflow and washout of the contrast agent in comparison with the surrounding parenchyma. At the same time, the pattern of recurrence corresponds to tumor recurrence, the pattern of residual tumor corresponds to residual malignant tissue, the pattern of fibrotic changes corresponds to the formation of scar tissue, the pattern of necrosis corresponds to the formation of a necrosis zone, the pattern of reactive changes corresponds to a necrosis zone with peripheral inflammation.

EFFECT: method provides an assessment of the cryoablation zone due to contrast patterns.

1 cl, 7 dwg, 6 tbl

Description

SUBSTANCE: invention relates to medicine, namely to methods for evaluating the results of surgical treatment in oncology, and can be used for postoperative assessment of the cryoablation zone in the treatment of kidney cancer.

Over the past decade, image-guided ablative therapy has gained popularity in the treatment of small tumors (Zhumaliyeva V.A. et al., 2014). Ablative techniques are an alternative to surgical treatment of renal cell carcinoma (RCC). These include interventions performed under the control of various imaging modalities with a variety of destructive effects. The most commonly used are: radiofrequency thermal ablation (RFA), microwave (MA) and cryoablation (CA).

Known conventional methods of control 1-6 months after CA by performing computed tomography (CT) or magnetic resonance imaging (MRI) with contrast. Efficiency assessment is based on the absence of vascularization in the area of education and a decrease in tumor volume (Gervais D.A. et. Al., 2005). After CA, the affected area on CT looks like an area with reduced contrast. Often, some of them show a gradual decrease in size and a thin heterogeneous ring around the periphery, which can persist several months after CA (Kim D.K. et al., 2019). During MPT, the ablated zone is characterized by a hyper- or isointense signal on T1-WI and hypointense on T2-WI (Rioja J., 2008; Zeccolini G. Et al., 2014).

There is evidence that CT or MRI with contrast after 3-4 months is preferable, since earlier control leads to frequent false positive results due to the presence of artifacts associated with post-ablative changes (Thumar A. B. et al., 2010 ).

Although CT and MRI show high diagnostic performance in evaluating treatment, contrast agents have nephrotoxicity (iodine-based contrast) or may induce nephrogenic systemic fibrosis (gadolinium-based contrast) and are therefore not recommended for patients with reduced renal function. .

In recent years, ultrasound is often used for control after CA (Venkatesan A.M. et al., 2011). This is due to the low cost, the absence of radiation exposure and the ability to work in real time. Grayscale echography has a number of limitations for high-quality visualization of the ablation zone, therefore, echocontrast can significantly increase the information content of the method for monitoring the patient's condition after treatment (Barozzi L. Et al., 2014)

A study by Meloni M.F. is known, in which he compared the results of CT and MRI with echocontrast in the observation of 29 patients with 30 kidney tumors treated with RFA. The agreement between the methods was 100%. Sensitivity of contrast-enhanced ultrasound is 96.6%, specificity is 100%, positive predictive value is 100%, negative predictive value is 98%. The author concluded that contrast-enhanced ultrasound (CEUS) is an effective alternative to CT or MRI in monitoring kidney tumors after RFA (Meloni M.F., 2008).

A similar study by Zeccolini G. and co-authors is known, in which the cryoablation zone was monitored in 25 patients. The average size of the tumor was 2.8 cm. According to the results of the biopsy, the clear cell variant of RCC was detected in all patients. During preoperative CEUS, the tumors were hypercontrast, the intensity distribution was more pronounced than the adjacent renal parenchyma in the arterial phase (Zeccolini G. Et al., 2014). CA was considered successful if there was no contrast enhancement of the ablation zone in both methods. The mean follow-up period was 3 years. There was no change in the size of the ablation zone during the entire time of control. In 24 patients, contrast enhancement was absent in both MRI and CEUS. In 1 case, during follow-up, CEUS and MRI revealed a histologically confirmed recurrence at a follow-up study 1 year after the procedure. The agreement between echo contrast and MRI was 100%. This study demonstrates the feasibility of using CEUS for monitoring renal CA.

In general, it should be recognized that publications on the use of CEUS for RFA or microwave ablation in the kidneys are presented quite fully in the world (mainly foreign) literature. Average sensitivity figures of 64-100% and specificity of 96.6-98.7% are also given (Hoeffel C. Et al., 2010; Kong W.T. et al., 2011).

A series of studies using CEUS as a control method after laparoscopic or percutaneous cryoablation are known (Wink M.H. et al., 2007; Zhu Q. Et al., 2005).

However, the main disadvantages of CEUS in the management of such patients is that, despite good results in assessing the area of kidney ablation, rapid contrast enhancement and washout can cause problems in image interpretation (Venkatesan A.M. et al., 2011). The location of the zone and the constitution of the patient also play a huge role, making it difficult to visualize the upper parts of the kidney with minimal intercostal access or the lower parts in patients with increased gas formation, as well as in obese patients (Sanz E. Et al., 2015). It is also important to keep in mind the high operator dependence of the method, especially in matters of control over the ablation zone, since the results can be significantly distorted in the hands of an inexperienced researcher (Zeccolini G. Et al., 2014; Sanz E. Et al., 2015).

Summarizing the above, it should be noted that CEUS is a highly informative diagnostic method that does not carry radiation exposure and allows monitoring after various options for ablative treatment of a kidney tumor. The limited availability of ultrasonic contrast agent (UHF) and other problematic issues currently hinder the widespread introduction of this approach into clinical practice, however, preliminary results indicate its promise and the need for further targeted research in this area.

Thus, the assessment of the ablation zone is an actual problem of modern medicine. Bolus contrast-enhanced CT occupies a leading position and remains the "gold standard" in the diagnosis of this condition. However, to date, the duration of the study, less availability and a number of absolute and relative contraindications are the limiting factors of the method.

High resolution, no radiation exposure, and sensitivity to low-velocity tumor blood flow are obvious advantages of the method. It is also important that the contrast agent is eliminated through the lungs, without additional load on the organ under study, especially when performing ablation in patients with severe somatic pathology and contraindications to surgical treatment.

To date, there are no clear recommendations on the timing of control after CA and other options for minimally invasive treatment; contrast patterns have not been sufficiently studied for a clear distinction between postablative changes and residual tumor tissue. Require in-depth study and comprehensive analysis of other aspects of the use of MPUS within the considered nosologies.

The technical result of the invention is the identification of contrast patterns for postoperative evaluation by ultrasound with echocontrast of the cryoablation zone in the treatment of kidney cancer in optimally set time periods.

The specified technical result is achieved in a method for postoperative assessment of the cryoablation zone in the treatment of kidney cancer by ultrasound examination (ultrasound) with an assessment of the shape, structure, contour, echogenicity, the presence of blood flow, in which ultrasound with echocontrast (ECU) is additionally performed in the cryoablation zone by 1-2 day, then repeated after 3, 6 months and after a year, an ultrasonic contrast agent (UHF) is injected in a volume of 1.5-2.0 ml, the patient is asked to hold his breath at the moment the drug appears in the cortical substance of the kidney and during the beginning of its leaching from kidneys, the following 5 perfusion contrast patterns are used to evaluate the cryoablation zone:

- reactive changes - a rounded zone or an irregularly shaped zone with the presence of an area of peripheral edema, characterized by the flow of a contrast agent, and an area of \u200b\u200bcentral necrosis;

- residual tumor - a zone with a pronounced asymmetry, residual parietal formation and a zone of necrosis;

- zones of necrosis - a rounded zone in the form of an anechoic avascular area with no contrast agent entering the structure of the ablation zone, has clear contours and a homogeneous structure;

- fibrous changes - a zone with the presence of fibrous septa without accumulation of a contrast agent with a possible background accumulation in the structure of the septa;

- recurrence - a zone with the presence of a nodular formation, characterized by an earlier entry and washing out of the contrast agent in comparison with the surrounding parenchyma;

assess the area of cryoablation depending on the type of pattern as follows:

perfusion pattern of recurrence - tumor recurrence, perfusion pattern of residual tumor - residual malignant tissue, perfusion pattern of fibrotic changes - formation of scar tissue, perfusion pattern of necrosis - formation of a necrosis zone, perfusion pattern of reactive changes - necrosis zone with peripheral inflammation.

The method is illustrated in Fig. 1-7 where:

In FIG. 1, 2 - methods for evaluating CEUS. Fig. 1 - a qualitative method for evaluating contrast characteristics by setting the ROI frames on the mass (red circle) and on the conditionally healthy kidney parenchyma (yellow circle). Fig. 2 - automatic construction of kinetic curves with axes of intensity and time of contrasting.

In FIG. 3 - perfusion pattern of necrosis.

In FIG. 4 - perfusion pattern of reactive changes.

In FIG. 5 - perfusion pattern of fibrotic changes.

In FIG. 6 - perfusion pattern of relapse.

In FIG. 7 - perfusion pattern of residual tumor.

The method is based on a study conducted between 2015 and 2020, including an analysis of the scan results of 20 patients with various kidney formations.

The main criterion for inclusion in the study, in addition to the presence of focal pathology as such, was the fact of preoperative CT of the abdominal organs, including scanning in the arterial and delayed phases, and CEUS.

Exclusion criteria: lack of full and adequate access to visualize the tumor and unchanged kidney parenchyma in the same plane of ultrasound scanning, as well as the impossibility of adequate control of respiratory movements during echocontrast.

The patients underwent a minimally invasive intervention in the form of CA of the pathological focus n-20 (100%). Minimally invasive treatment was performed in the presence of contraindications for surgical intervention due to severe somatic diseases, the presence of a single kidney, as well as old age. The group analyzed the possibilities of CEUS in assessing postoperative changes after organ-preserving and minimally invasive treatment: the presence and volume of the necrosis zone, the ischemic zone, as well as areas suspicious for continued tumor growth or recurrence, in particular, in patients with limited ability to perform contrast-enhanced CT.

Ultrasound was performed for all patients without exception and consisted of a grayscale B-mode examination, CFM, EDC, and subsequent CEUS. Scanning was performed on Aloka Noblus, Hi Vision Avius and Hi Vision Ascendus devices (Hitachi, Japan) using a 2-8 MHz broadband abdominal convex probe. The study scheme included a survey scan of the abdominal organs with further detailed sequential study of the kidney parenchyma and targeted study of focal formations.

At the final stage of ultrasound, contrast-enhanced ultrasound was performed.

Before starting the procedure, the allergic anamnesis must be clarified. All patients received voluntary informed consent to the manipulation, a conversation was held about the need to breathe superficially with minimal excursion of the abdominal wall during scanning.

On the day of the study, patients were preliminarily placed with an 18 G catheter in a peripheral vein, usually in the left arm. CEUS of the kidneys was carried out using the Sonovue preparation (Bracco Swiss S.A., Switzerland), international name: Sulfur hexafluoride.

Dilution of the contrast agent was carried out according to the method specified in the instructions: "1 bottle of dry matter must be diluted in 5 ml of 0.9% NaCl solution supplied in the kit using a special injector." Further, the substances were mixed with the formation of microbubbles and the acquisition of a solution of a uniform translucent color. Then, 1.5-2.0 ml of the solution ready for administration was drawn into a separate syringe.

Standardly, when performing CEUS of the kidneys, an average of 1.0 ml of a contrast agent prepared according to the above method is injected, however, a deterioration in contrast enhancement indicators was noted, in the form of a slowdown in delivery and a decrease in the intensity of contrast enhancement in patients with chronic kidney disease (CKD) with a history of n- 15 (75%). This group of patients was injected with a larger amount (1.5-2.0 ml) of a contrast agent to achieve an improvement in contrast enhancement. In 85% of cases, an increase in contrast intensity was achieved. Characteristics of tumor enhancement in this group of patients were similar to patients without CKD.

We started the procedure with the optimal positioning of the patient. As mentioned above, we always tried to achieve a clear localization of the sensor above the area of interest (taking into account respiratory movements), which includes both the pathological focus and the surrounding tissue of the kidney in order to conduct a comparative analysis of these structures. Then the device activated the mode with two parallel images in real time (contrast mode and B-mode). Immediately prior to injection, the content of the syringe was assessed and all macroscopic air bubbles were removed.

The drug was administered in a volume of not more than 2.0 ml (average 1.5 ml) per person in order to avoid hypercontrast of the renal parenchyma. Immediately after this, 10 ml of a 0.9% NaCl solution were additionally injected. Simultaneously with the introduction of a contrast agent, the recording of the cine loop was turned on and the stopwatch was activated. Taking into account that the kidneys are quite mobile during respiration, in order to obtain the most informative qualitative indicators, patients were asked to hold their breath in the cortical phase (the moment the drug appears in the renal cortex) and during the beginning of VHF washout from the kidney.

The results of CEUS were assessed both visually and using specialized software. During post-processing, the ROI (region of interest) function was used (Fig. 1).

The zones of interest were set on the following objects: the area of maximum uniform contrast enhancement of the tumor and the surrounding parenchyma. The obtained accumulation and washout curves were studied both using the statistical data processing methods proposed in the software package and manually.

The CEUS method was used to examine 20 patients with kidney neoplasms who underwent minimally invasive surgical treatment in the form of a CA tumor. The age of patients ranged from 35 to 90 years and averaged 66±21 years for men and 65±30 years for women. The distribution of patients according to the relevant characteristics is given in Table. one.

As follows from Table. 1, the majority of those surveyed were women (57.5%). The mean age of the patients was 66±21 years. The average body mass index - 28.7±7.7 kg/m ² (significantly exceeded the upper limit of normal).

All formations were morphologically verified: during resection, the postoperative material was evaluated, in the case of CA, a pre-manipulation trepan biopsy of the formations was performed. The distribution by nosology and type of operation is shown in Table. 2.

From Table. It follows from Table 2 that the total number of malignant tumors was n-18 (90%), all of them were represented by the clear cell variant of the ICR. Benign tumors turned out to be n-2 oncocytomas (10%), all of them were subjected to CA.

Ultrasound was performed according to the method described above and included scanning in grayscale B-mode, color flow and CEUS.

CT with bolus contrast enhancement was used as a reference method of radiation diagnostics.

As mentioned above, the optimal time parameters for dynamic monitoring of the group of patients under consideration are being actively discussed and have not yet been finally determined, therefore, based on literature data (Gervais D.A. et. al., 2005; Thumar A.B. et. al. ., 2010; Stewart-Merrill, S.B., et. al. 2015) and work experience, we decided to conduct control studies at the following times:

1-2 days. Evaluation of the resection area for early postoperative complications (ischemia, hematoma), which could occur more often after resection, as well as to visualize a possible residual tumor, which could be determined after CA.

3 months. The probability of continued tumor growth due to non-optimal CA, which was not recognized immediately after the procedure due to the physiological characteristics of the formed necrosis zone, was assessed.

6 months. Evaluation for the absence of recurrence.

1-2 years. Evaluation for the absence of recurrence.

The terms of the actually performed studies are presented in Table. 3.

From Table. 3 it follows that CEUS was performed in all patients for a period of 1-2 days after the manipulation. Such a volume of research is associated with the need to monitor patients after surgery for incomplete removal of the tumor or the presence of early postoperative complications (swelling, ischemia). CEUS, a more accessible method that does not have radiation exposure, which is why CT at this control period was performed in a much smaller number of patients. At this time, in 1 patient (5%) after CA, continued tumor growth was detected.

Control after 3 months was carried out in the group after CA, since there are no clear recommendations on the timing of monitoring patients after this manipulation. CEUS and CT in this group of patients were performed in the vast majority, with rare exceptions. The main goal of control at this rather early period is the need to assess the intervention area for early recurrence. At this time, assessing the area of interest in both ways, no pathological changes were detected.

Six months later, the majority of patients underwent a follow-up examination as planned. Most of the patients underwent a follow-up examination, with the exception of patients who did not appear on time due to the epidemiological situation and due to individual restrictions (a number of patients have elevated creatinine). In patients, data for relapse were not obtained by the results of both methods.

Also, the control examination was carried out for a period of 1-2 years after the organ-preserving treatment. All patients underwent both methods of examination at this stage. 3 relapses (15%) were found. According to the biopsy results, RCC was verified in all three cases.

In the CEUS mode, the area of the treatment was evaluated in order to register the nature and pattern of contrast enhancement.

For the differential diagnosis of recurrence and fibrotic changes in patients after CA, we assessed the US characteristics, including CEUS, presented in Table. four.

Based on the data of morphological verification and long-term follow-up, continued growth was established in 1 case (5%), and recurrence occurred in 4 cases (20%): 1 patient after 6 months and 3 patients 1-2 years after surgery. As a result of comparing this information and the considered US characteristics, the most frequent criteria corresponding to cicatricial changes and recurrence in the surgical area were formulated.

Cicatricial and postoperative changes were characterized by an even contour, a homogeneous structure, more often increased echogenicity, avascularity in CDI, and the absence of VHF accumulation in the CA area (Fig. 2).

It should be noted that the very nature of the impact in CA is significantly different from resection, and therefore, in minimally invasive treatment, in order to simplify the differential diagnosis of early postoperative changes and continued tumor growth, it makes sense to systematize the semiotics of CEUS, taking into account various options and stages of transformation of the pathological node after appropriate intervention. ,

In the course of the study, the 5 most common contrast patterns were identified and described (Fig. 1-5).

Thus, we found that in the early postoperative period (days 1-2) we most often encountered a reactive contrast pattern of n-17 (85%), while the zone was most often acontrast in the center and had a background flow of VHF along the periphery of the zone of the performed intervention, which is probably due to the formation of a zone of inflammatory infiltration. At the same time, 2 patients (10%) had a perfusion pattern of necrosis, and one (5%) had a perfusion pattern of residual tumor. In the latter, a massive peripheral, hypervascular component of the tumor with a central zone of necrosis was visualized. Biopsy confirmed residual tumor.

3 months after the intervention, a pattern of reactive changes was determined in 5 patients (27.7%), which is probably due to the small size of the zones of postoperative changes and the difficulty of objective diagnosis between the reactive pattern and the pattern of necrosis when assessing the manipulation zone less than 10 mm. The perfusion pattern of necrosis was determined in 13 patients (72.2%).

A follow-up examination conducted after 6 months revealed that in 8 patients (53.3%) a pattern of fibrotic changes was determined, which is probably associated with the beginning of the formation of scar tissue in the area of the intervention. Also, at this follow-up examination, 1 patient (6.7%) was found with a perfusion pattern of relapse, which we interpreted as a malignant formation in the area of the intervention. Perfusion patterns of necrosis and reactive changes were less common, in 5 (33.4%) and 1 (6.7%) patients, respectively.

After 1-2 years, we found 3 patients (15%) with a perfusion pattern of relapse, which was also interpreted as the growth of a malignant tumor and was confirmed by CT or biopsy. By this time, in 13 patients (65%), a pattern of fibrotic changes was determined, which was due to the replacement of the tumor with connective tissue. 4 patients (20%) also had an annular pattern.

These patterns significantly improve the effectiveness of the method in diagnosing changes after CA. Summarized data on the number of patients and identified contrast patterns are presented in Table. 5.

Contrast-enhanced CT scan was performed in all patients as a reference method of radiodiagnosis.

Postoperative changes in the group of patients with CA (n-20) were assessed: the structure of the ablation zone, the contour and the presence of visible accumulation in the area of the treatment.

When comparing the results of mUSI and CT with bolus contrast enhancement in terms of detecting tumor recurrence after organ-preserving and minimally invasive treatment, no differences were found. When comparing data on the presence of recurrence on the basis of morphological verification and information collected in the course of radiological studies, the following figures were obtained - Table. 6.

From Table. 6 it follows that both methods received 1 false-negative result (relapse was mistaken for inflammation). In this observation, at the stage of the early postoperative period, the minimal formation along the contour of the CA zone was regarded as early inflammatory changes. However, during a trephine biopsy, a material was obtained, labeled as a clear cell variant of RCC.

In another, also a single observation, a false positive diagnosis was made. Both on CEUS and on the basis of CT results, benign lesions are mistaken for malignant ones. This was due to pronounced cicatricial changes with an ambiguous central zone, giving background contrast in both cases. According to the results of the biopsy, malignant cells were not obtained.

The effectiveness of the CEUS method was: sensitivity in the group was 80%; specificity - 93.3%; accuracy - 90%. PCR = 80%; PCR = 93.3%.

Thus, contrast-enhanced mUSI is an effective method of postoperative control after organ-preserving and minimally invasive treatment, demonstrating indicators as close as possible to the results of CT.

The claimed method makes it possible to identify contrasting patterns for postoperative assessment by ultrasound with echocontrasting of the cryoablation zone in the treatment of kidney cancer at optimally set time periods.

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Claims (8)

A method for postoperative assessment of the cryoablation zone in the treatment of kidney cancer by ultrasound examination (ultrasound) with an assessment of the shape, structure, contour, echogenicity, presence of blood flow, characterized in that ultrasound with echocontrast (CEUS) is additionally performed in the cryoablation zone for 1-2 days, then repeat after 3, 6 months and after a year, an ultrasonic contrast agent (UHF) is injected in a volume of 1.5-2.0 ml, the patient is asked to hold his breath at the moment the drug appears in the cortical substance of the kidney and during the beginning of its leaching from the kidney, for assessments of the cryoablation area use the following 5 perfusion contrast patterns: - reactive changes - a rounded zone or an irregularly shaped zone with the presence of an area of peripheral edema, characterized by the flow of a contrast agent, and an area of \u200b\u200bcentral necrosis; - residual tumor - a zone with a pronounced asymmetry, residual parietal formation and a zone of necrosis; - zones of necrosis - a rounded zone in the form of an anechoic avascular area with no contrast agent entering the structure of the ablation zone, has clear contours and a homogeneous structure; - fibrous changes - a zone with the presence of fibrous septa without accumulation of a contrast agent with a possible background accumulation in the structure of the septa; - recurrence - a zone with the presence of a nodular formation, characterized by an earlier entry and washing out of the contrast agent in comparison with the surrounding parenchyma; assess the area of cryoablation depending on the type of pattern as follows: perfusion pattern of recurrence - tumor recurrence, perfusion pattern of residual tumor - residual malignant tissue, perfusion pattern of fibrotic changes - formation of scar tissue, perfusion pattern of necrosis - formation of a necrosis zone, perfusion pattern of reactive changes - necrosis zone with peripheral inflammation.

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