Pulmonary metastasectomy - A retrospective comparison of surgical outcomes after laser-assisted and conventional resection

Laser assisted pulmonary metastasectomy promises a low local recurrence rate

Pulmonary metastasectomy (PM) is consensually performed in a parenchyma-sparing manner to preserve functionally healthy lung tissue. However, this may increase the risk of local recurrence at the surgical margin. Laser assisted pulmonary metastasectomy (LPM) is a relatively recent innovation that is especially useful to resect multiple metastatic pulmonary nodules. In this study we investigated the rate of local recurrence after LPM and evaluated the influence of various clinical and pathological factors on local recurrence. Retrospectively, a total of 280 metastatic nodules with different histopathological entities were studied LPM from 2010 till 2018. All nodules were resected via diode-pumped neodymium: yttrium-aluminum-garnet (Nd:YAG) 1,318 nm laser maintaining a safety margin of 5 mm. Patients included were observed on average for 44 ± 17 months postoperatively. Local recurrence at the surgical margin following LPM was found in 9 nodules out of 280 nodules (3.21%). Local recurrence at the surgical margin occurred after 20 ± 8.5 months post operation. Incomplete resection (p =  < 0.01) and size of the nodule (p = < 0.01) were associated with significantly increased risk of local recurrence at the surgical margin. Histology of the primary disease showed no impact on local recurrence. Three and five-year survival rates were 84% and 49% respectively. Following LPM, the rate of local recurrence is low. This is influenced by the size of the metastatic nodules and completeness of the resection. Obtaining a safety margin of 5 mm seems to be sufficient, larger nodules require larger safety margins.

Laser-assisted lung metastasectomy: a systematic review

Laser-assisted resection (LAR) of pulmonary metastases offers several potential advantages compared to conventional surgical techniques. However, the technical details, indications and outcomes of LAR have not been extensively reviewed. We conducted a systematic literature search to identify all original articles reporting on LAR of pulmonary metastases. All relevant outcomes, including morbidity rate, R0 rate, pulmonary function tests, overall- (OS) and relapse-free survival (RFS) rates were collected. Additionally, a comparison between outcomes obtained by laser-assisted and conventional resection techniques was provided. Of 2629 articles found by the initial search, 12 were selected for the systematic review. Following LAR, the R0 rate ranged between 72 and 100% and the morbidity rate ranged from 0 to 27.5%. The postoperative decline in forced expiratory volume in 1 s varied between 3.4 and 11%. Median OS and RFS were 42-77.6 months and 9-34.1 months, respectively. Compared with patients treated by other resection techniques, patients treated by LAR frequently had a higher number of metastases and a higher rate of bilateral disease. Despite this, no significant differences were observed in R0 rate, morbidity rate, and median OS rate, while only 1 study found a lower RFS rate in the LAR cohort. Although selection bias limits the comparability of outcomes, the findings of this review suggest that LAR is a valid alternative to conventional procedures of lung metastasectomy. The main difficulties of this technique consist in the adoption of a video-assisted thoracoscopic approach, and in the pathologic assessment of resection margins.

New Prognostic Score (Essen Score) to Predict Postoperative Morbidity after Resection of Lung Metastases

BACKGROUND

Pulmonary metastasectomy (PM) is a widely accepted surgical procedure. This study aims to investigate postoperative morbidity and mortality after PM and develop a score to predict high-risk patients.

METHODS

We retrospectively investigated all patients undergoing a PM in our institution from November 2012 to January 2023. Complications were defined as the diagnosis of any new disease after the PM up to 30 days after the operation.

RESULTS

1284 patients were identified. At least one complication occurred in 145 patients (11.29%). Only one patient died during the hospital stay. Preoperative cardiovascular comorbidities (OR: 2.99, 95% CI: 1.412-3.744, p = 0.01), major lung resections (OR: 2.727, 95% CI: 1.678-4.431, p < 0.01), repeated pulmonary metastasectomy (OR: 1.759, 95% CI: 1.040-2.976, p = 0.03) and open thoracotomy (OR: 0.621, 95% CI: 0.415-0.930, p = 0.02) were identified as independent factors for postoperative complications. Based on the above independent factors for postoperative morbidity, the Essen score was developed (overall correct classification: 94.6%, ROC-Analysis: 0.828, 95% CI: 0.795-0.903).

CONCLUSION

PM is a safe surgical procedure with acceptable morbidity and low mortality. The aim of the Essen score is to identify patients that are associated with risk for postoperative complications after PM.

Laser pulmonary metastasectomy preserves parenchyma: a single-centre retrospective study from the United Kingdom

Background

Pulmonary metastasectomy (PME) is a modality increasingly employed to control oligometastatic disease from a variety of solid tumours.

We present data from a single UK centre, following the introduction of laser-assisted surgery (LAS) using the Limax® 120 Nd:Yag laser (Gebrüder Martin GmbH & Co. KG, Tuttlingen, Germany).

Methods

All patients undergoing PME between September 2015 and August 2018 were included in our study. Those undergoing LAS were compared to a control of conventional stapled wedge metastasectomy (SWM). Data was analysed retrospectively from a prospective kept database. Statistical analysis was performed using JASP (Version 0.14.1).

Results

Fifty-seven procedures in 46 patients, were included in the final analysis. Demographic data was similar at baseline between the LAS and SWM group, with colorectal cancer being the most common primary, 44/57 (77%). LAS was favoured in patients who had previously undergone pulmonary metastasectomy, 9/12 (75%). Patients in the LAS group had a smaller parenchymal volume resected (MD 30.6 cm3, p = 0.0084), with a lower incidence of clear histological marginal resection (11/27 vs 29/30, p < 0.0001); but no difference in operative time, morbidity, patient-reported outcome measures, or local recurrence between the two groups at 2 years. LAS was associated with a lower procedural cost (MD £452.92, p < 0.0001).

Conclusions

Laser-assisted pulmonary metastasectomy presents a safe and acceptable alternative to traditional stapled wedge resection, with notable parenchymal-sparing, no discernible learning curve, and lower direct costs.

Lung Metastatectomy: Can Laser-Assisted Surgery Make a Difference?

BACKGROUND

Resection of lung metastases with curative intention in selected patients is associated with prolonged survival. Laser-assisted resection of lung metastases results in complete resection of a high number of lung metastases, while preserving lung parenchyma. However, data concerning laser lung resections are scarce and contradictory. The aim of this study was to conduct a systematic review to evaluate the utility of laser-assisted pulmonary metastasectomy.

METHODS

An electronic search in MEDLINE (via PubMed), complemented by manual searches in article references, was conducted to identify eligible studies.

RESULTS

Fourteen studies with a total of 1196 patients were included in this metanalysis. Laser-assisted surgery (LAS) for lung metastases is a safe procedure with a postoperative morbidity up to 24.2% and almost zero mortality. LAS resulted in the resection of a high number of lung metastases with reduction of the lung parenchyma loss in comparison with conventional resection methods. Survival was similar between LAS and conventional resections.

CONCLUSION

LAS allows radical lung-parenchyma saving resection of a high number of lung metastases with similar survival to conventional methods.

Initial Airtightness of the Lung Parenchyma After Transection of the Interlobar Fissure - Monopolar Cutter, Stapler Versus Nd: YAG Laser

INTRODUCTION

Every lobectomy requires the transection of the interlobar fissure. Resection surfaces must be airtight in order to avoid leakage and infection. Using an ex vivo model based on porcine lung, we compared three techniques with respect to initial airtightness at different inspiratory pressures.

MATERIALS AND METHODS

In the first technique (group 1), we transected the interlobar fissure with a monopolar cutter and overstitched the edges of the resection area with a monofilament thread. In the second technique (group 2), the interlobar fissure was cut with a stapling device. In the third technique (group 3), the interlobar fissure was cut using a laser fibre connected to an Nd: YAG laser. The resection areas were not overstitched; 15 transections were performed in each group.

RESULTS

In group 1, three parenchymatous bridges leaked starting at a pressure of 25 mbar. In the other two groups, all preparations were airtight at this pressure. If the ventilation pressure was increased up to 40 mbar, all seams in group 1 were leaky at a pressure of 35 mbar. Four staple seams were airtight at a pressure of 40 mbar. In group 3, 11 preparations (73.3 %) were airtight up to a pressure of 40 mbar.

CONCLUSIONS

Based on our results, the use of an Nd: YAG laser is suitable for the transection of the interlobar fissure. In effect, this technique compares well with the other techniques examined.

Lung Metastases: Current Surgical Indications and New Perspectives

Pulmonary metastasectomy is an established treatment that can provide improved long- term survival for patients with metastatic tumor(s) in the lung. In this mini-review, we discuss the state of the art of thoracic surgery in surgical management of lung metastases which actually occurs for a large part of surgical activity in thoracic surgery department. We describe the principles of surgical therapy that have been defined across the time, and that should remain the milestones of lung metastases treatment: a radical surgery and an adequate lymphadenectomy. We then focus on current surgical indications and report the oncological results according to the surgical approach (open vs. mini-invasive), the histological type and number of lung metastases, and in case of re-metastasectomy. Finally, we conclude with a brief overview about the future perspectives in thoracic surgery in treatment of lung metastases.

Local Effects of a 1940 nm Thulium-Doped Fiber Laser and a 1470 nm Diode Laser on the Pulmonary Parenchyma: An Experimental Study in a Pig Model

The lungs are a common site of metastases from malignant tumors. Their removal with a minimal but safe tissue margin is essential for the long-term survival of patients. The aim of this study was to evaluate the usefulness of a 1940 nm thulium-doped fiber laser (TDFL) and a 1470 nm diode laser (DL) in a pig model of lung surgery that involved the incision and excision of lung tissue. Histopathological analysis was performed on days 0 and 7 after surgery. Neither TDFL nor DL caused significant perioperative or postoperative bleeding. Histological analysis revealed the presence of carbonized necrotic tissue, mixed fibrin-cellular exudate in the superficial zone of thermal damage and bands of deeper thermal changes. The mean total width of thermal damage on day 0 was 499.46 ± 61.44 and 937.39 ± 109.65 µm for TDFL and DL, respectively. On day 7, cell activation and repair processes were visible. The total width of thermal damage was 2615.74 ± 487.17 µm for TDFL vs. 6500.34 ±1118.02 µm for DL. The superficial zone of thermal damage was narrower for TDFL on both days 0 and 7. The results confirm the effectiveness of both types of laser in cutting and providing hemostasis in the lungs. TDFL caused less thermal damage to the lung parenchyma than DL.

["Tissue Handling" in Thoracic Surgery - Results of a Delphi Expert Consensus Conference of the German Society for Thoracic Surgery]

BACKGROUND

The aim of this working group of the German Society for Thoracic Surgery (DGT) was to develop an expert consensus based on the Delphi method to define "tissue handling" and depict intraoperative handling of specific anatomical structures during thoracic surgery.

METHODS

Invited experts (thoracic surgery specialists; n = 93) completed two consecutive rounds of electronic Delphi questions on four main topics: transection of lung parenchyma, dissection/separation of pulmonary vessels, angioplasty/vascular anastomoses, and bronchus settling closure/plasty/anastomosis. Consensus was set at ≥ 75% agreement. At the subsequent expert conference, the results of the Delphi surveys were discussed and TED voting was used to try to reach consensus.

RESULTS

In each case, 66 (71%) answers were given in the first round of questions and 33 (35%) in the second round. Disputed questions were evaluated again by a final vote at the expert conference (54 participants; average participation 55%). The term "tissue handling" includes all procedures for dissection, transection, sealing, and reconstruction of various autologous tissues in the context of thoracic surgery (100% consensus). Similarly, the term "angioplasty expansion" was defined with a 97% consensus. Consensus was reached mainly for the technique of transecting the lung parenchyma using stapling suture devices, the recommendation of covering anastomoses as well as bronchial stump after pretreatment (> 75%).

CONCLUSIONS

This expert consensus describes for the first time the concept of tissue handling in thoracic surgery. Furthermore, this Delphi process led to a comprehensive current inventory of different intraoperative procedures in German thoracic surgery with derived consensual recommendations for tissue handling of lung parenchyma, vessels and bronchial structures.

Surgical Morbidity and Lung Function Changes After Laser-Assisted Pulmonary Metastasectomy: A Prospective Bicentric Study

Objective: The surgical resection of pulmonary metastases is associated with a survival benefit in selected patients. The use of laser devices for pulmonary metastasectomy (PM) is believed to facilitate the complete resection of metastases while preserving a maximum of healthy parenchyma. This is a prospective study to evaluate surgical outcome including the changes of lung function after laser–assisted surgery (LAS).

Methods: A total of 77 operations in 61 patients in which PM was carried out in a curative intent were analyzed. A 1.320 nm diode-pumped Nd: YAG-Laser was used for resection of the metastases. Surgical and clinical data were collected using a standardized form and postoperative lung function changes 3 and 6 months after surgery were assessed using whole body plethysmography and diffusion capacity for carbon monoxide (DLCO). Size and distance of metastases to the pleural surface were measured radiologically.

Results: A median of two metastases were resected per operation (range 1–13). The median duration of postoperative air leak was 1 day (range 0–11). LAS associated postoperative minor and major complications were observed in 4 (5%) cases and 1 (1%) case, respectively; there were no mortalities. The analysis of perioperative lung function showed that mean VC 3 months after surgery was reduced by 11 %, FEV1 by 11% and median DLCO by 11% (all p < 0.0001). There was almost no recovery of lung function between 3 and 6 months in the whole cohort. Patients with two or less metastases showed a recovery of lung function after 3 months regarding DLCO (p = 0.003). Decline of DLCO in the whole cohort correlated with the number of resected metastases at 3 months (r = 0.45, p = 0.006) and at 6 months (r = 0.42, p = 0.02) as well as depth of metastases in the parenchyma at 6 months (r = 0.48, p = 0.001).

Conclusions: LAS is a safe and effective method for PM even for higher numbers of metastases, with short duration of postoperative air leak and little morbidity. Number and depth, but not size of metastases affect lung function changes after resection.

Determination of initial airtightness after anatomical laser segmentectomy in an ex vivo model

If a pulmonary pathology can be removed by anatomical segmentectomy, the need for lobectomy is obviated. The procedure is considered oncologically equivalent and saves healthy lung tissue. In every segmentectomy, lung parenchyma must be transected in the intersegmental plane. Using an ex vivo model based on porcine lung, three transection techniques (monopolar cutter + suture, stapler, and Nd:YAG laser) are to be compared with respect to their initial airtightness. At an inspiratory ventilation pressure of 25 mbar, all three preparations were airtight. Upon further increase in ventilation pressure up to 40 mbar, the laser group performed best in terms of airtightness. Since thanks to its use of a laser fibre, this technique is particularly suitable for minimally invasive surgery; it should be further evaluated clinically for this indication in the future.

Results of redo pulmonary metastasectomy

Repeat surgical resection (redo) for pulmonary metastases is a questionable, albeit intriguing topic. We performed an extensive review of the literature, to specifically analyze results of redo pulmonary metastasectomies. We reviewed a total of 3,523 papers. Among these, 2,019 were excluded for redundancy and 1,105 because they were not completely retrievable. Out of 399 eligible papers, 183 had missing information or missing abstract, while 96 lacked data on survival. A total of 120 papers dated from 1991 onwards were finally included. Data regarding mortality, major morbidity, prognostic factors and long-term survivals of the first redo pulmonary metastasectomies were retrieved and analyzed. Homogeneity of data was affected by the lack of guidelines for redo pulmonary metastasectomy and the risks of bias when comparing different studies has to be considered. According to the histology sub-types, redo metastasectomies papers were grouped as: colorectal (n=42), sarcomas (n=36), others (n=20) and all histologies (n=22); the total number of patients was 3,015. Data about chemotherapy were reported in half of the papers, whereas targeted or immunotherapy in 9. None of these associated therapies, except chemotherapy in two records, did significantly modify outcomes. Disease-free interval before the redo procedure was the prevailing prognostic factor and nearly all papers showed a significant correlation between patients’ comorbidities and prognosis. No perioperative mortality was reported, while perioperative major morbidity was overall quite low. Where available, overall survival after the first redo metastasectomy ranged from 10 to 72 months, with a 5-years survival of approximately 50%. The site of first recurrence after the redo procedure was mainly lung. Despite the data retrievable from literature are heterogeneous and confounding, we can state that redo lung metastasectomy is worthwhile when the lesions are resectable and the perioperative risk is low. At present, there are no “non-surgical” therapeutic options to replace redo pulmonary metastasectomies.

Local lung coagulation post resection: an ex-vivo porcine model

Following non-anatomical resection of lung parenchyma with a Nd:YAG laser, a coagulated surface remains. As ventilation starts, air leakage may occur in this area. The aim of the present study was to investigate, whether additional coagulation either before or after ventilation has an additional sealing effect. Freshly slaughtered porcine heart-lung blocks were prepared. The trachea was connected to a ventilator. Using a Nd:YAG laser (wavelength: 1320 nm, power: 60 W), round lesions (1.5 cm in diameter) with a depth of 1.5 cm were applied to the lung using an 800-μm laser fiber (5 s per lesion). Group 1 (n = 12) was control. Additional coagulation was performed in group 2 (n = 12) without and in group 3 (n = 12) with ventilation restarted. Air leakage (ml) from the lesions was measured. The thickness of each coagulation layer was determined on histological slices. Differences between individual groups were analyzed by one-way ANOVA (significance p < 0.05). After resection, 26.2 ± 2.7 ml of air emerged from the lesions per single respiration in group 1. Air loss in group 2 was 24.6 ± 2.5 ml (p = 0.07) and in group 3 23.7 ± 1.8 ml (p = 0.0098). In comparison to groups 1 and 2 thickness of the coagulation layers in group 3 was significantly increased. After non-anatomical porcine lung resection with a Nd:YAG laser, additional coagulation of the ventilated resection area can reduce air leakage.

Surgery versus stereotactic radiotherapy for treatment of pulmonary metastases. A systematic review of literature

It is not clear as to which is the best treatment among surgery and stereotactic radiotherapy (SBRT) for lung oligometastases. A systematic review of literature with a priori selection criteria was conducted on articles on the treatment of pulmonary metastases with surgery or SBRT. Only original articles with a population of patients of more than 50 were selected. After final selection, 61 articles on surgical treatment and 18 on SBRT were included. No difference was encountered in short-term survival between pulmonary metastasectomy and SBRT. In the long-term surgery seems to guarantee better survival rates. Mortality and morbidity after treatment are 0–4.7% and 0–23% for surgery, and 0–2% and 4–31% for SBRT. Surgical metastasectomy remains the treatment of choice for pulmonary oligometastases.

Patients with metastatic cancer with a limited number of deposits may benefit from surgical removal or irradiation of tumor nodules in addiction to chemotherapy. Surgical resection has been demonstrated to improve survival and, in some cases, can be curative. Stereotactic radiotherapy is emerging as a less invasive alternative to surgery, but settings and implications of the two treatments are profoundly different. The two techniques show similar results in the short-term, with lower complications rates for radiotherapy, while in the long-term surgery seems to guarantee higher survival rates.

Is laser-assisted resection preferable to lobectomy for pulmonary metastasectomy?

The aim of this study was to investigate if laser-assisted resection is appropriate for large and/or central lung metastases, when stapler wedge resection is not feasible, to determine whether this technique can be an alternative to lobectomy. All patients who underwent laser-assisted resection for large and/or central metastases were selected for the study. For comparison, patients who underwent lobectomy for metastases between 2005 and 2017 were reviewed. All resections were performed with a 1318-nm Nd:YAG laser. Perioperative features and long-term oncological outcomes were investigated. Some aspects and drawbacks of laser resection were also investigated. Among 89 patients, 42 (47%) underwent laser resection and 47 underwent lobectomy. Complete resection was achieved in 91% of laser resections and in 98% of lobectomies. The operative time, postoperative drainage time, and length of stay were significantly shorter in patients who underwent laser resection than in those who underwent lobectomy. Severe postoperative complications tended to be more frequent after lobectomy. The 5-year survival was 66% and 54% after laser resection and lobectomy respectively; the 5-year disease-free survival was 35% and 32% after laser resection and lobectomy respectively. No differences were found in long-term outcomes between the two techniques. Our experience showed that laser resection, when performed for large/central metastases, resulted in comparable survival and obtained better perioperative outcomes with respect to lobectomy. We believe that laser resection can be proposed as a reliable and advantageous lung-sparing technique, as an alternative to lobectomy for metastasectomy, when stapler wedge resection is not feasible.

Pulmonary laser-assisted metastasectomy is associated with prolonged survival in patients with colorectal cancer

Background

Pulmonary metastases develop in 10-15% of patients with colorectal cancer. Surgical metastasectomy currently provides the only hope for a cure for these patients. The aim of this study was to analyze the expanding role of pulmonary metastasectomy in the context of laser-assisted surgery (LAS) vs. non-laser-assisted surgery (NLAS).

Methods

We performed a single-center retrospective analysis of 204 patients who underwent curative pulmonary metastasectomy for colorectal cancer between 01/2005 and 12/2016. The main endpoint was survival. The Kaplan-Meier method was applied for statistical analysis and survival rates were compared with the log rank test.

Results

Median follow-up was 53 months. A total of 267 metastases were resected in 154 operations in the NLAS group (median: 1) vs. 438 metastases in 122 operations in the LAS group (median: 5; P<0.0001). The interval between treatment of the primary tumor and the first pulmonary metastasectomy was significantly shorter in the LAS group (19 vs. 32 months; P=0.008). Anatomical resections were significantly reduced using LAS, 8% vs. 23% respectively. Despite more negative predictors in the LAS group, there was no statistically significant difference in overall disease-specific 5-year survival (70% LAS vs. 58% NLAS; P=0.18).

Conclusions

Survival after pulmonary metastasectomy has previously been shown to correlate with a low number of metastases and a longer disease-free interval. However, with the tissue-saving LAS technique complete resectability can be achieved in patients with more metastases and long-term survival is possible for selected patients.

Limax Nd:YAG laser-assisted thoracoscopic resection of pulmonary metastases; a single centre's initial experience

INTRODUCTION

Pulmonary metastasectomy and indeed redo-pulmonary metastasectomy are now commonly performed thoracic surgical procedures. The air-sealant, haemostatic, and necrotic properties of the KLS Martin Limax Nd:YAG laser at 1.318 μm make it an ideal tool for limited lung resection such as metastasectomy. We present our initial experience of thoracoscopic laser metastasectomy.

METHODS

We reviewed data from the first seven patients in our unit to undergo thoracoscopic laser metastasectomy, in particular, patient age, gender, primary malignancy, primary treatment, complications, length of stay (LOS), and final histopathology. All procedures were performed using a two- or three-port thoracoscopic technique with some lesions requiring CT-guided wire localisation. A single drain was inserted via the camera port site and was removed upon confirmation that there was no air leak.

RESULTS

Seven patients underwent thoracoscopic laser wedge metastasectomy of eight lesions in our centre between February 2017 and October 2017. The median age was 61 years. The primary disease was colorectal carcinoma in five cases, eccrine carcinoma in one case, and high-grade uterine leiomyosarcoma in one case. Only one patient had a prolonged air leak in the other six cases; the drain was removed on post-operative day 1. The median post-operative LOS was 1 day. All patients had confirmed metastatic disease with clear resection margins on histopathology.

CONCLUSION

In our early experience, thoracoscopic laser wedge metastasectomy is a safe and efficient method for performance of pulmonary metastasectomy. We experienced a low complication rate and a short post-operative stay.

Pulmonary metastasectomy in sarcoma-experiences with laser-assisted resection

Background

Previous data suggest a survival benefit in well selected patients with extrathoracic sarcoma after pulmonary metastasectomy. Different techniques have been described for pulmonary metastasectomy; however laser-assisted surgery (LAS) was suggested to provide the best outcome in patients with higher numbers of metastases.

Methods

Data were extracted from a prospectively maintained institutional database and a total of 83 patients who underwent pulmonary metastasectomy at our clinic in the last 11 years were identified.

Results

We analyzed a total of 106 operations of which LAS was performed in 46 and conventional resection in 60 cases. Significantly more metastases were resected in the LAS group compared to the conventional group [median, interquartile range (IQR): 6.5 (2.0-11.0) vs. 1.0 (1.0-3.5); P<0.0001]. Despite this difference the number of tumor recurrences was similar in both groups [64% tumor recurrences in the LAS group and 58% in the conventional group, odds ratio (OR) =1.3, P=0.6]. Furthermore, overall survival (OS) was comparable with a median survival of 77.6 and 29.0 months and 2- and 5-year survival rates of 71% and 63% as well as 53% and 36% in the respective cohorts [hazard ratio (HR) =0.74, P=0.43].

Conclusions

Using LAS a significantly higher number of metastases were removed while producing similar long-term results as compared to patients treated by other techniques. Expectably, recurrence rates in metastasized sarcoma patients remain high with either surgical method. Future studies will have to evaluate possible advantages provided by LAS in a prospective manner.