Systematic review of ablation techniques for the treatment of malignant or aggressive benign lesions in children

Fernando M. Gomez . Premal A. Patel . Samuel Stuart · Derek J. Roebuck

Received: 24 October 2013 /Revised: 13 February 2014 / Accepted: 9 April 2014 C Springer-Verlag Berlin Heidelberg 2014

Abstract

Background Ablation techniques are widely used for solid malignant tumors in adults. There is no large series assessing the effectiveness of local ablative therapies in the treatment of malignant or aggressive benign lesions in children.

Objective To review the existing evidence on the techniques and results of ablation for pediatric solid malignant or aggres- sive benign tumors.

Materials and methods We searched MEDLINE for papers published between 1995 and 2012 that reported outcomes of radiofrequency, microwave and cryoablation, interstitial laser therapy, irreversible electroporation and percutane- ous ethanol injection for patients younger than 18 years old. Data collection included factors related to the pa- tient, tumor biology, ablation technique and cancer- specific endpoints. Additional series of predominantly adults including data on patients younger than 18 years old were also identified.

Results We identified 28 patients treated by ablation in 29 regions: 5 patients undergoing ablation for liver lesions, 9 patients for lung metastases, 11 patients for bone and/or soft tissue and 4 patients for kidney or pancreas. The ablation was performed to treat primary tumors, local recurrences and metastases. The histology of the tumors was osteosarcoma in 6 patients, Wilms tumor in 3, rhabdomyosarcoma in 3, hepatoblastoma in 3, desmoid tumor in 3, adrenocortical carcinoma in 2 and a single case each of leiomyosarcoma,

Ewing sarcoma, paraganglioma, solid-pseudopapillary neo- plasm, sacrococcygeal teratoma, hepatic adenoma, juxtaglomerular cell tumor and plantar fibromatosis. Eighteen of the patients (64%) experienced a complication, but only 6 (21%) of these needed treatment other than sup- portive care.

Conclusions Although ablative techniques are feasible and promising treatments for certain pediatric tumors, large mul- ticenter prospective trials will be needed to establish efficacy.

Keywords Percutaneous ablation . Neoplasms . Children . Systematic review

Introduction

Local ablation techniques are widely used in adults for the treatment of both benign and malignant lesions [1-5]. They can be divided, depending on the mechanism they use to cause injury, into thermal therapies such as radio- frequency ablation, percutaneous cryoablation, microwave ablation and interstitial laser thermotherapy; chemical ab- lative techniques, typified by percutaneous ethanol injec- tion, and irreversible electroporation, which alters the elec- trical conductivity and permeability of the cell membrane by means of high-voltage pulses, causing both cellular disruption and thermal damage [6]. In some cases, these techniques are included in the algorithms of treatment of oncological diseases at the same level as more aggressive techniques such as surgical resection [7], in others they represent an alternative to surgery in patients who are not candidates for resection due to high anesthetic risk or other circumstances [2, 3, 5]. These techniques may also have an impact on the immune system of patients by activating a tumor-associated antigen-specific T cell re- sponse [8-10]. Local ablation can be carried out with

F. M. Gómez Hospital Clinic de Barcelona, C/ Villarroel 170 Barcelona, Spain e-mail: fegomez@clinic.ub.es

curative or palliative intent, either alone or in combination with systemic (immunotherapy or chemotherapy) [11] or locoregional therapies (radiotherapy or chemoembolization) [5, 12]. The effect of systemic chemotherapy may be enhanced by the physiological changes produced by ther- mal ablation [11]. Furthermore, ablation can sometimes be used as a complement to surgery, individualizing the treat- ment for each lesion in a single patient [13]. These treatments have been applied to tumors located in almost every organ in the human body including the liver, kidney, lung, musculoskeletal system and pancreas [1-13]. Although thermal ablation is widely regarded as the treat- ment of choice for osteoid osteoma in extraspinal locations [14] and thermal and chemical ablation techniques have been used for thyroid or benign vascular tumors, among others [15, 16], the use of these techniques still remains exceptional in children with malignancy. In this systematic review we aim to report the techniques and results of ablation for solid malignant or borderline tumors in children.

Materials and methods

We limited the search start to 1995, as the application of these techniques was infrequent even in adults before then. No language restriction was applied. We followed the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses: the PRISMA statement (http://www.prisma-statement.org/statement.htm). We performed a search in MEDLINE including the terms: (radiofrequency) OR (microwave) OR (percutaneous ethanol) OR (interstitial laser) OR (irreversible electropo- ration) OR cryoablation NOT (osteoid osteoma) AND (malignan* OR tumor). For each paper we extracted: title, authors, year of publication, journal name, type and sub- type of journal (medical, surgery, radiology or others and general or pediatrics), type of study, strength of evidence according to the Oxford Centre for Evidence-based Medicine, number of patients (including only those <18 years), mean of time to progression (time from inclu- sion to radiological progression), mean of time to recur- rence (time from inclusion to recurrence), mean time of overall survival (time from inclusion to death) and mean lesion diameter or volume. For each individual patient we recorded: age, sex, body mass, type of tumor (histology), nature of diagnosis (primary or metastatic), size of tumor (diameter or volume), location, other treatment after abla- tion, ablation technique (radiofrequency ablation, micro- wave ablation, percutaneous cryoablation, percutaneous ethanol injection, irreversible electroporation, interstitial laser thermotherapy), electrode size, anesthesia type (gen- eral [GA], local with or without sedation), number of

lesions, number of ablation sessions, guidance technique (US, MRI, CT, fluoroscopy), technical success (proper positioning of the ablation device into the target area with completion of the planned treatment), clinical success (accomplishing clinical goal of ablation), duration of hos- pitalization following ablation, overall survival, complica- tions and status at the end of the study (died of disease - DOD, alive with evidence of disease - AWED, or no evidence of disease - NED). Abstracts were screened to identify the relevance of the retrieved reports. Further screening of cited references was undertaken to detect any studies that may have been missed from our initial search. Two reviewers independently extracted data from all studies onto a predefined data collection form. Any discrepancies were resolved by consensus among four of the authors (D.J.R, S.S., P.A.P, F.G.M). Due to the small number of studies reporting results of ablation in children, we aimed to include every case describing the use of the techniques stated above for malignant and locally aggres- sive tumors. We reviewed the resulting cases according to the target organ ablated (liver, lung, bone and/or soft tissues, and kidney or pancreas).

Results

Adding the exception of the Hoffer et al. paper [17], which is a phase I study, relevant data was missing for many of the reported cases. The age was reported in all cases. The mean age of the 28 patients identified was 9 years (range: 1 day to 17 years). The sex was reported in 18 patients (64%), 13 females and 5 males. Body mass was reported in only 5 of the 28 patients (18%), with a median of 16 kg (range: 13-41 kg). The histology of all tumors was reported: osteosarcoma in 6 patients (21%), Wilms tumor in 3 (11%), rhabdomyosarcoma in 3 (11%), hepatoblastoma in 3 (11%), desmoid tumor in 3 (11%), adrenocortical carcinoma in 2 (7%) and leiomyosarcoma, Ewing sarcoma, paraganglioma, solid-pseudopapillary neo- plasm, sacrococcygeal teratoma, hepatic adenoma, juxtaglomerular cell tumor and plantar fibromatosis in 1 case each (3%). The nature of the lesion (primary, recurrent or metastatic) was reported in 28 of the 29 locations ablated (96%). Among the 29 locations treated, according to chronology, there were primary tumors in 11 cases (38%), local recurrence in 4 cases (14%) and me- tastases in 12 cases (42%). The diameter or volume of the ablated lesions was described in 26 of the 28 patients (92%). The paper describing the most patients [17] did not list the individual size of the 56 lesions treated, but reported a range from 0.13 ml to 750 ml (median: 7 ml; mean: 46 ml). In the 14 remaining patients the diameter ranged from 8 mm to 170 mm (median: 18 mm; mean:

45 mm). We identified 28 patients treated by means of ablation in 29 regions (one of the patients underwent both lung and bone radiofrequency ablation). Five patients underwent liver ablation (18%), 9 patients lung ablation (32%), 11 patients bone and/or soft-tissue ablation (39%) and 4 patients underwent kidney or pancreas ablation (14%). After the 29 ablations, the need for additional treatment was explained in 28 cases (97%): In 14 cases (50%) the patients did not need further treatment and in 16 cases systemic chemotherapy alone or together with surgery, surgery alone or together with embolization, or radiotherapy (conventional or brachytherapy) were used. The technique was radiofrequency ablation in 26 cases (90%), percutaneous cryoablation in 2 (7%) and percuta- neous ethanol injection in 1 (3%). Excluding the patient treated by means of percutaneous ethanol injection, the type of cryoprobe or electrode needle and size was report- ed in 15 cases (54%). The anesthetic technique was GA in 28 cases (97%) and local anesthetic with sedation in 1 (3%). The total number of ablated lesions was 65 (me- dian: 2) in 92 ablation sessions (median: 3). In Hoffer’s [17] series the median hospital stay was 3 days (range: 2-25 days). Survival was reported for 26 of the 28 patients (93%), with mean overall survival of 22 months (median: 18 months; range: 0.7-96 months).

Bone and soft-tissue ablations (Table 1)

We identified 11 patients who underwent bone and soft- tissue ablation in six papers [17-22]. The mean and median age of the patients was 10 years. Four were female and two male, and in five patients the sex was not reported. The weight was only reported in one patient, who weighed 41 kg. The histology of the tumors was rhabdomyosarcoma in three patients, desmoid tumor in two and leiomyosarcoma, paraganglioma, osteosarcoma, Ewing sarcoma, plantar fibromatosis and teratoma in one each. The location of the ablation was soft tissue in six patients (presacral, breast, tensor fascia lata, lumbar mus- cles, oral cavity and plantar fascia) and bone in five (maxilla, radius, femur, ribs and sacrum). In four cases, the tumors were primary; in two local recurrences, in two metastases and for three patients the nature of the lesion was not reported. The mean of the reported diameters of the ablated lesions was 70 mm, and in six cases the size was not reported. A total of 17 lesions were ablated in 32 sessions. Four patients received additional systemic thera- py (chemotherapy in three and antiviral therapy in one), one with additional embolization. Two patients were treated with additional regional therapy (embolization and radiotherapy) without systemic therapy. Except for four patients (one percutaneous cryoablation and three

radiofrequency ablation), the type of needle used in the procedure was not reported. All of the treatments were performed under GA and except for one patient (with Ewing sarcoma undergoing percutaneous cryoablation) the ablative technique used was radiofrequency ablation. In six cases, the guidance technique was CT; in four, CT and US were combined, and in one case, US was the only modality used. Technical success was achieved in nine cases. Clinical success was obtained in eight patients. The outcome was unreported in one. The du- ration of post-ablation hospitalization was only specified in two cases (both less than 1 day). Mean overall survival of the patients for whom this data was reported was 15 months (median: 12 months). Eight patients suffered a complication, but only two needed additional active treatment (surgery). Recurrence or progression was observed in five patients and complete tumor ablation in another five: in one case it was not documented. At the time of the reports, five patients were NED, three DOD and three were AWED.

Ablation of lung metastases (Table 2)

Nine patients reported in two papers underwent radiofrequen- cy ablation for lung metastases [17, 23]. The mean age of the patients was 11 years (median: 12 years). The sex and body mass were only reported in one case, a 4-year-old boy weighing 12.8 kg. The histology of the primary tumors was osteosarcoma in six, Wilms tumor in one, adrenocortical carcinoma in one and hepatoblastoma in one. The diameter of the metastases was not specified in any of the cases, but the mean volume in the eight children reported by Hoffer et al. [17] was 5 ml. However, this volume includes the excluded patients due to be older than 17 years old that could not be excluded to extract the real volume of the included patients. A total of 34 lesions (mean: 4 per patient) were treated in 45 sessions (mean: 5; median: 3). Five patients received addi- tional chemotherapy (two of them accompanied by surgery), one underwent radiotherapy and three did not receive any other treatment. All of the treatments were CT-guided radio- frequency ablation, performed under GA. Clinical success was reported for two patients and achieved in one with adre- nocortical carcinoma. Forty-five percent of the lung lesions ablated in the Hoffer’s paper [17] were completely ablated after the first-time treatment with no recurrence, but again, patients older than 17 years of age could not be excluded to extract the real volume of the included patients. The length of stay in the hospital was not reported in any of the treatments. The mean overall survival of the patients was 19 months (median: 13 months). All the patients suffered complications caused by the lung radiofrequency ablation: FEV1 reduction and diaphragmatic hernia in two patients each, and pain,

Table 1 Reported ablation of malignant or aggressive benign bone and soft-tissue tumors in children
ReferenceAgeSexMass (kg)HistologyLocation of tumorSize (mm)Number of lesionsNumber of ablationsOther treatment after ablation
[17]16 yearsNRNRRhabdomyosarcomaBreast metastasisNR11Chemotherapy
[17]13 yearsNRNRRhabdomyosarcomaBone metastasis (maxilla)NR12Embolization, chemotherapy
[17]16 yearsNRNROsteosarcomaBone metastasis (radius)NR11Radiotherapy
[17]13 yearsNRNRPlantar fibromatosisSoft tissue (foot)NR615None
[17]9 yearsNRNRLeiomyosarcomaRibsNR22Antiviral therapy
[18]10 yearsM41ParagangliomaBone metastasis (femur)1211None
[19]9 yearsFNREwing sarcomaBone recurrence (sacrum)NR11 (5 needles)Celecoxib
[20]1 dayFNRSacrococcygeal teratomaSoft tissue primary (pelvis)17011Embolization, surgery
[21]14 yearsFNRDesmoid tumorSoft tissue (tensor fascia lata)10014None
[21]5 yearsMNRDesmoid tumorSoft tissue (lumbar muscle)5513None
[22]10 yearsFNRRhabdomyosarcomaSoft-tissue recurrence (oral cavity)2411None
ReferenceAblation techniqueAblation deviceAnesthesia techniqueGuidance techniqueTechnical successClinical successDuration of hospitalizationPatient statusComplicationManagement of complication
[17]RFANRGAUS, CTYesNoNRDOD 5 monthsPainSymptomatic
[17]RFANRGAUS, CTNoNoNRDOD 5 monthsTrismusNone
[17]RFANRGAUS, fluoroscopyYesYesNRDOD 12 monthsNone
[17]RFANRGAUS, CTNoYesNRAWED 34 monthsParesthesiaNone
[17]RFANRGACTYesYesNRAWED 26 monthsHypoxiaSupportive
[18]RFANRGACTYesNRNRNRHypertension (non-blocked)None
[19]PCAPerCryoGACTYesYesNRAWED 9 monthsFecal and urinary incontinenceSupportive
[20]RFANRGACTYesYesNRNED 12 monthsNone
[21]RFAStar-Burst XLGACTYesYes<1 dayNRNone
[21]RFAStar-Burst XLGAUSYesYes<1 dayNRSkin burnSurgery
[22]RFACool-tip 20 mmGACTYesYesNRNED 18 monthsTrismusNone

All reported procedures were performed under general anesthesia

NR not reported, M male, F female, RFA radiofrequency ablation, PCA percutaneous cryoablation, DOD died of disease, AWED alive with evidence of disease, NED no evidence of disease

Table 2 Reported CT-guided radiofrequency ablation (RFA) of lung metastases in children
ReferenceAge, ySexTumor mass, kgPrimary tumorTreatment after ablationAblation techniqueElectrode typeNumber of lesionsNumber of ablationsTechnical successClinical successPatient status and age at eventComplicationsManagement of complication
[17]10NRNROsteosarcomaRadiotherapyRFANR22NRNRDOD 8 monthsFEV1 reductionSupportive
[17]14NRNROsteosarcomaNoneRFANR23NRNRNED 48 monthsPainSupportive
[17]12NRNROsteosarcomaChemotherapyRFANR44NRNRDOD 12 monthsHypoxiaSupportive
[17]16NRNROsteosarcomaSurgery, chemotherapyRFANR11NRNRDOD 13 monthsBradycardiaSupportive
[17]4NRNRAdrenocortical carcinomaSurgery, chemotherapyRFANR416yesNRDOD 27 monthsDiaphragmatic herniaSurgery
[17]16NRNROsteosarcomaChemotherapyRFANR66NRNRDODFEV1 reductionNone
12 months
[17]10NRNRWilms tumorChemotherapyRFANR99NRNRAWED 33 monthsDiaphragmatic herniaSurgery
[17]12NRNROsteosarcomaNoneRFANR33NRNRDOD 15 monthsDyspneaSupportive
[23]4M12.8HepatoblastomaNoneRFACool-tip 20 mm31nonoDODBronchovascularAttempted coagulation
21 daysfistula

with RFA probe

All procedures were performed under general anesthesia

NR not recorded, M male, FEV1 forced expiratory volume in 1 s, AWED alive with evidence of disease

hypoxia, bradycardia, dyspnea and bronchovascular fistula with hemorrhage in one patient each. The treatment of the complications was surgical in two patients. In the patient with bronchovascular fistula, there was an attempt to coagulate a hemorrhage with the radiofrequency ablation needle. Supportive care was sufficient in five cases, and there was no need for treatment in the patient with FEV1 reduc- tion. There was recurrence in one patient and progression in two. At the time of reporting, seven patients were DOD, one was AWED and one was NED. Cryoablation of lung metastases has not yet been reported in children.

Liver ablation (Table 3)

Five patients underwent liver ablation [13, 24-26]. Mean age was 4 years (median: 3 years). Three patients were female and two male. The weight was only reported for one patient (12.6 kg). The histology was hepatoblastoma in two patients, and adrenocortical carcinoma, hepatic adenoma and Wilms tumor in one each. There were two primary tumors, two metastases and one local recurrence. The diameter was report- ed in four cases (mean: 19 mm). Seven lesions were ablated in seven sessions. US was the image guidance (in two cases it was intraoperative) and technical and clinical success was achieved in all five cases. Mean overall survival was 44 months (median: 36 months). There were no complications and except for one patient with unreported data, no progres- sion or tumor recurrence was described. All five patients were NED at the time of reporting.

Kidney or pancreas ablation (Table 4)

Four patients were treated with ablation for retroperitoneal tumors [27-30]. The mean age was 11 years, and all patients were female. The weight was only reported in one case (16 kg). The histology was Wilms tumor in two, juxtaglomerular cell tumor in one, and solid and papillary epithelial neoplasm of the pancreas in one patient. The ablation was performed in the kidney (2), surgical bed following nephrectomy (1) and pancreas (1). In each case the tumor was primary, except for one patient with local recurrence of Wilms tumor [28]. The median diameter of the ablated lesions was 18 mm. The diameter was unre- ported in one patient [28]. All of the lesions were treated with radiofrequency ablation, and in all the cases the electrode size and type were reported. A total of five lesions were ablated in six sessions. One patient subse- quently received brachytherapy [28] and another surgery due to failure of the radiofrequency ablation [29]. In all the treatments GA was used; image guidance was CT in three and intraoperative US in one. Technical success was

accomplished in all four cases. Clinical success was ob- tained in three patients. The duration of hospitalization was only specified for one procedure (1 day) [27]. Mean overall survival was 12 months. Only one patient suffered a complication (ab- dominal pain), but this did not require treatment. Recurrence or progression was observed in one patient. At the time of the reporting, two patients were NED, one was AWED and one had died of another cause (leukemia).

Discussion

As expected, there is very limited experience with ablation in children. Even though the manuscript summarizes the overall experience, it may not provide significant help in decision- making for surgeons/interventional radiologists to decide ap- propriate use of ablation use in children. The number of cases and pathology treated with these techniques is also small to draw conclusions about efficacy of ablative techniques in pediatric pathology.

This systematic review confirms that ablative thera- pies are feasible in children with primary, recurrent or metastatic tumors in various organs. Most reports im- plicitly describe treatment with palliative intent in pa- tients that in many cases have failed to respond to almost every other available therapy. This selection for poor candidates may contribute to a failure to achieve similar results to those observed in adults.

Because pediatric cancer is relatively rare, and indications for ablative therapies are few, the only way to evaluate indi- vidual modalities in specific clinical situations will be to develop multicenter international studies.

It is notable that many published cases are poorly described, in terms of both the technical aspects of the procedures and the clinical outcomes. These deficiencies should be addressed in future research studies. To this end, we propose a minimum data set for future reports (Table 5). These include recommended data to improve the quality of the reported cases and to facilitate their interpretation in future systematic reviews and meta- analysis about pediatric tumor ablation. These data concern:

- The patient (age, sex, weight, target organ function tests, pain evaluation pre- and post-procedure, quality of life assessment).

- The tumor (tumor histology, tumor location including possible factor reducing efficacy, tumor chronology, tu- mor volume, tumor markers).

- The technique (clinical indication and clinical success definition, technical success definition, ablated volume, neoadjuvant or adjuvant therapies, type and size of elec- trode or antenna or probe, energy generated, ablation

Table 3 Reported ablation of liver tumors in children
ReferenceAge, ySexTumor mass, kgHistologyTumor size, mmLiver segments involvedOther treatment after ablationAblation techniqueElectrode type (if RFA)Anesthesia typeNumber of lesionsNumber of ablationsGuidance techniquePatient status and age at event
[24]2F12.6Adrenocortical carcinoma metastasis156/7NonePEIGA23USANED 39 months
[25]13MNRHepatic adenoma356NoneRFANRGA11USANED 24 months
[13]2.5FNRHepatoblastomaNR5/8 and 8Chemotherapy (SIOPEL-3HR)RFALe Veen 35 mmGA21US at laparotomyANED 96 months
[13]3FNRWilms tumor metastasis158Chemotherapy (SIOP 2001)RFALe Veen 0 mmGA11US at laparotomyANED 36 months
[26]2MNRHepatoblastoma (recurrent)104NoneRFAHiTT 20-30 mmLA, sedation11USANED 24 months

All procederes were reported to be technically and clinically successful. Duration of hospitalization was not reported. No complications were reported F female, M male, NR not reported, PEI percutaneous ethanol injection, RFA radiofrequency ablation, GA general anesthesia, LA local anesthesia ANED alive, no evidence of disease

Table 4 Reported ablation of renal and pancreatic lesions in children
ReferenceAge, ySexTumor mass, kgHistologyTumor diameter, mmLocationOther treatment after ablationElectrode typeNumber of lesionsNumber of ablationstechnique GuidanceDuration of hospitalizationage at event or Patient status and follow-upComplications
[27]5F16Wilms tumor18KidneyNoneLe Veen 20 mm11CT1 dayAWED 14 monthsNone
[28]11FNRRecurrent Wilms tumorNRRenal fossaBrachytherapyCool-tip 20 mm12CTNRDied of leukemia 9.5 monthsNone
[29]11FNRSolid- pseudopapillary neoplasm120PancreasSurgeryRITA 1500X22US at laparotomyNRNED 12 monthsAbdominal pain, pyrexia, abnormal LFT
[30]17FNRJuxtaglomerular cell tumor8KidneynoneLe Veen11CTNRNED 14 monthsNone
35 mm

NR not reported, AWED alive with evidence of disease, LFT liver function tests

All reported patients were female. All procedures were radiofrequency ablation, performed under general anesthesia, and were reported as technically and clinically successful

Table 5 Required data for reporting local ablation for cancer

Patient

Ageª

Sexª

Weightb

Target organ function testsb

Pain evaluation pre- and post-procedureb

Quality of life assessmentb

Tumor

Tumor histologyª

Tumor location including possible factor reducing efficacyª

Primary, local recurrence, distant metastasesª

Tumor volume (at least diameter)ª

Tumor markersb

Technique

Clinical indication and clinical success definitionª

Technical success definitionª

Ablated volumeª

Neoadjuvant or adjuvant therapiesª

Type and size of electrode, antenna, etc., and energy generateda

Ablation protocolª

Image guidance techniqueª

Number of lesions treatedª

Number of treatments for every lesion in a single sessionª

Number of sessions in a single lesionª

Complications and their level by WHO/SIR classificationª

Hospitalization lengthb

Image follow-up techniqueª

Response criteria (RECIST, mRECIST) and response classificationª

Cancer-related relevant endpoints

Time follow-upª

Overall survivalª

Disease-free survivalª

Time to recurrenceª

Time to progressionb

Time to local recurrenceª

Event-free survivalb

Progression-free survivalb

a Necessary

b Recommended

RECIST response evaluation criteria in solid tumors

mRECIST modified response evaluation criteria in solid tumors

WHO World Health Organization

SIR Interventional Radiology

protocol, image guidance technique, number of lesions treated, number of treatments for every lesion in a single session, number of sessions in a single lesion, complica- tions and its level by OMS/SIR classification, hospitali- zation length, image follow-up technique, response criteria [response evaluation criteria in solid tumors,

modified response evaluation criteria in solid tumors, criteria of the European Association for the Study of the Liver] response classification).

- The cancer-related relevant endpoints (time follow-up, overall survival, disease-free survival, time to recurrence, time to progression, time to local recurrence, event-free survival, progression-free survival).

Conclusion

Although ablative techniques are feasible and promising treat- ments for certain pediatric tumors, large multicenter prospec- tive trials will be needed to establish efficacy. As ablation procedures for malignant tumors in children are infrequent, reporting data in a structured way becomes an essential instru- ment to perform analysis in future systematic reviews.

Conflicts of interest None.

References

1. Vogl TJ, Naguib NN, Lehnert T et al (2011) Radiofrequency, micro- wave and laser ablation of pulmonary neoplasms: clinical studies and technical considerations-review article. Eur J Radiol 77:346-357

2. Gangi A, Tsoumakidou G, Buy X et al (2010) Quality improvement guidelines for bone tumor management. Cardiovasc Intervent Radiol 33:706-713

3. Palussière J, Italiano A, Descat E et al (2011) Sarcoma lung metas- tases treated with percutaneous radiofrequency ablation: results from 29 patients. Ann Surg Oncol 18:3771-3777

4. Martin RC 2nd, McFarland K, Ellis S et al (2013) Irreversible electroporation in locally advanced pancreatic cancer: potential im- proved overall survival. Ann Surg Oncol 20:S443-S449

5. Lencioni R, Crocetti L (2012) Local-regional treatment of hepatocel- lular carcinoma. Radiology 262:43-58

6. Goldberg SN, Grassi CJ, Cardella JF et al (2009) Image-guided tumor ablation: standardization of terminology and reporting criteria. J Vasc Interv Radiol 20:S377-S390

7. European Association for Study of Liver; European Organisation for Research and Treatment of Cancer (2012) EASL-EORTC clinical practice guidelines: management of hepatocellular carcinoma. Eur J Cancer 48:599-641, Erratum in: Eur J Cancer 48:1255-1256

8. Vogl TJ, Wissniowski TT, Naguib NN et al (2009) Activation of tumor-specific T lymphocytesafter laser-induced thermotherapy in patients with colorectal liver metastases. Cancer Immunol Immunother 58:1557-1563

9. Mizukoshi E, Yamashita T, Arai K et al (2013) Enhancement of tumor-associated antigen-specific T cell responses by radiofrequency ablation of hepatocellular carcinoma. Hepatology 57:1448-1457

10. Rao P, Escudier B, de Baere T (2011) Spontaneous regression of multiple pulmonary metastases after radiofrequency ablation of a single metastasis. Cardiovasc Intervent Radiol 34:424-430

11. Ahmed M, Moussa M, Goldberg SN (2012) Synergy in cancer treatment between liposomal chemotherapeutics and thermal abla- tion. Chem Phys Lipids 165:424-437

12. Ikuta S, Kurimoto A, Iida H et al (2012) Optimal combina- tion of radiofrequency ablation with chemoradiotherapy for locally advanced pancreatic cancer. World J Clin Oncol 3:12- 14

13. van Laarhoven S, van Baren R, Tamminga RY et al (2012) Radiofrequency ablation in the treatment of liver tumors in children. J Pediatr Surg 47:e7-e12

14. Rimondi E, Mavrogenis AF, Rossi G et al (2012) Radiofrequency ablation for non-spinal osteoid osteomas in 557 patients. Eur Radiol 22:181-188

15. Hill RH 3rd, Shiels WE 2nd, Foster JA et al (2012) Percutaneous drainage and ablation as first line therapy for macrocystic and microcystic orbital lymphatic malformations. Ophthal Plast Reconstr Surg 28:119-125

16. Kim YJ, Baek JH, Ha EJ et al (2012) Cystic versus predominantly cystic thyroid nodules: efficacy of ethanol ablation and analysis of related factors. Eur Radiol 22:1573-1578

17. Hoffer FA, Daw NC, Xiong X et al (2009) A phase 1/pilot study of radiofrequency ablation for the treatment of recurrent pediatric solid tumors. Cancer 115:1328-1337

18. Pappas L, Seefelder C (2009) Anesthetic consideration for radiofre- quency ablation of a suspected paraganglioma metastasis in a child. Paediatr Anaesth 19:913-914

19. Lessard AM, Gilchrist J, Schaefer L et al (2009) Palliation of recurrent Ewing sarcoma of the pelvis with cryoablation and somatosensory-evoked potentials. J Pediatr Hematol Oncol 31: 18-21

20. Cowles RA, Stolar CJ, Kandel JJ et al (2006) Preoperative angiog- raphy with embolization and radiofrequency ablation as novel ad- juncts to safe surgical resection of a large, vascular sacrococcygeal teratoma. Pediatr Surg Int 22:554-556

21. Ilaslan H, Schils J, Joyce M et al (2010) Radiofrequency ablation: another treatment option for local control of desmoid tumors. Skelet Radiol 39:169-173

22. Nashida Y, Yamakado K, Kumamoto T et al (2007) Radiofrequency ablation used for the treatment of frequently recurrent rhabdomyosarcoma in the masticator space in a 10- year-old girl. J Pediatr Hematol Oncol 29:640-642

23. Burgoyne LL, Pereiras LA, Laningham F et al (2008) Near-fatal acute bronchovenous fistula in a child undergoing radiofrequency ablation of a metastatic lung tumor. Paediatr Anaesth 18:1131-1133

24. Hara F, Kishikawa T, Tomishige H et al (2003) A child with adreno- cortical carcinoma who underwent percutaneous ethanol injection therapy for liver metastasis. J Pediatr Surg 38:1237-1240

25. Rocourt DV, Shiels WE, Hammond S et al (2006) Contemporary management of benign hepatic adenoma using percutaneous radio- frequency ablation. J Pediatr Surg 41:1149-1152

26. Ye J, Shu Q, Li M et al (2008) Percutaneous radiofrequency ablation for treatment of hepatoblastoma recurrence. Pediatr Radiol 38:1021-1023

27. Brown SD, Vansonnenberg E, Morrison PR et al (2005) CT- radiofrequency ablation of pediatric Wilms tumor in a solitary kid- ney. Pediatr Radiol 35:923-928

28. Gandhi S, Meech SJ, Puthawala MA et al (2005) Combined com- puted tomography-guided radiofrequency ablation and brachythera- py in a child with multiple recurrences of Wilms’ tumor. J Pediatr Hematol Oncol 27:377-379

29. Sugito K, Kusafuka T, Hoshino M et al (2010) Application of radiofrequency ablation for giant solid pseudopapillary tumor of the pancreas. Pediatr Int 52:e29 e31

30. Kirkham AP, Ho SG, Paterson RF et al (2008) Treatment of a juxtaglomerular tumor with radiofrequency ablation. Urology 71: 168.e1-4