Monoclonal gammopathy of clinical signifi cance with osteosclerotic lesions - a case report and a literature review.

INTRODUCTION: Multiple myeloma is a common plasma cell neoplasia usually accompanied by the formation of osteolytic foci, whereas osteosclerotic myeloma is a very rare form of plasma cell dyscrasia. When osteosclerotic myeloma is detected, osteosclerotic foci are usually part of the POEMS syndrome. Osteosclerotic myeloma without other manifestations of the POEMS syndrome is an unusual finding. CASE DESCRIPTION: In a 46-year-old woman, osteosclerotic changes of the temporoparietal region caused soft tissue induration over this lesion, which initiated further investigation. Imaging studies subsequently showed multiple osteosclerotic foci in the skull. Examination of blood proteins revealed 8 g/L of IgG-lambda monoclonal immunoglobulin, subclass IgG1. In search of the cause of the osteosclerotic changes, FDG-PET/CT was performed, which revealed no FDG accumulation, i.e., no other tumor (breast or stomach cancer). Low-dose CT showed irregular bone structure, but not significant osteolytic or osteosclerotic foci. To map the extent of osteosclerotic changes, NaF-PET/CT imagination followed, which revealed multiple spots with high fluoride accumulation. A parietal bone biopsy showed osteosclerosis with minor clonal plasma cell infiltration. Trepanobioptic bone marrow sampling revealed an infiltration of bone marrow with atypical plasma cells in 8%. Flow-cytometric examination of bone marrow showed 0,37% of plasma cells, however predominantly (91%) clonal with lambda expression. MRI of the brain identified asymptomatic meningeal thickening. There was no evidence of POEMS syndrome in the patient; thus, we concluded the diagnosis as monoclonal gammopathy of clinical significance with osteosclerosis which was previously termed osteosclerotic multiple myeloma. CONCLUSION: Monoclonal gammopathy of clinical significance (MGCS) with osteosclerotic skeletal changes, documented on CT and multiple foci with intensive osteoneogenesis, documented on NaF-PET/CT without evidence of POEMS syndrome, is an extremely rare form of plasma cell dyscrasia. This publication documents the unique clinical manifestations of IgG-lambda type plasma cell proliferation without signs of POEMS syndrome and the role of NaF-PET/CT imaging. Classification of this disease as MGSC with osteosclerotic manifestations is more consistent with the indolent nature of the disease with a significantly better prognosis, compared with multiple myeloma.

Overview of histiocytic and dendritic disorders by the 5th version of WHO Classifi cation of Hematolymphoid Tumours from 2022.

BACKGROUND: Histiocytoses are rare disorders characterized by the accumulation of macrophages, dendritic cells, or monocyte-derived cells in various tissues and organs of children and adults, with a wide range of clinical manifestations, presentations, and histology. The histiocytoses are classified according to the WHO Classification, the last version of which was published in 2022, or according to the Histiocyte Society Classification, with the last version published in 2016. PURPOSE: This text provides an overview of histiocytoses as described in the WHO Classification 2022.

Retroperitoneal fibrosis - diagnosis and treatment.

Idiopathic retroperitoneal fibrosis (IRF) is a rare condition characterized by the development of a peri-aortic and peri-iliac tissue showing chronic inflammatory infiltrates and pronounced fibrosis. Ureteral entrapment with consequent obstructive uropathy is one of the most common complications which can lead to acute renal failure and, in the long term, to varying degrees of chronic kidney disease. Common symptoms at onset include lower back, abdominal or flank pain. Pain is frequently referred to the hip, to the groin and to the lateral regions of the leg, often with nocturnal exacerbations and not responding to position changes. The disease is commonly associated with signs of systemic inflammatory response (malaise, fever, and anorexia and weight loss). Glucocorticoids are considered the cornerstone of the therapy. The use of other immunosuppressive agents, including cyclophosphamide, azathioprine, methotrexate, mycophenolate mofetil and biological agents such as rituximab, tocilizumab and infliximab have been reported as a valuable option mostly in case reports, cases series and small studies. These agents allowed to reduce cumulative dose of glucocorticoids and their adverse effects. Combined therapy is preferable for all patients who suffer from significant glucocorticoid- related toxicity or in cases where glucocorticoids alone are insufficient to treat the condition.

Rosai-Dorfman-Destombes disease - histiocytic disorder with inflammatory manifestation.

BACKGROUND: Rosai-Dorfman-Destombes disease (RDD) is a rare histiocytosis characterized by accumulation of activated histiocytes within affected tissues. Although the immunophenotype of this disease was described, the pathophysiology of this disease is still not sufficiently understood. Recent studies have found NRAS, KRAS, MAP2K1, and ARAF mutations in RDD lesions, raising the possibility of a clonal origin in some forms of RDD while in other cases reactive origin or association with other malignant and autoimmune disease is supposed. RDD is a widely heterogeneous entity with a range of clinical phenotypes occurring in some patients in association with autoimmune or malignant diseases. Its therapy should reflect the localization of the disease. Monotherapy with glucocorticoids is sufficient only in limited disease. In patients with advanced disease, combined nodal and extranodal forms of RDD need more intensive therapy. In older publications, antimetabolites, vinca alkaloids and prednisone were used; in recent publications, remissions after cladribine, rituximab, sirolimus, thalidomide, lenalidomide and cobimetinib were described. PURPOSE: This text summarizes current knowledge about this rare disease and reviews the therapeutic options.

Slow increase of bilirubin concentration during administration of lenalidomide, bortezomib and dexamethasone for multiple myeloma (unmasking previously undiagnosed Gilbert syndrome) and disappearance of necrobiotic xanthogranuloma after complete remission of multiple myeloma.

BACKGROUND: Lenalidomid ranks among immunomodulatory drugs. There are a few of the more common side effects, like a higher risk of venous trombembolism or diarrhea. Other side effects are rare. The hyperbilirubinemia described in this article can be assigned to them. In our case, the increase of bilirubin was associated with unrecognized Gilbert syndrome. CASE DESCRIPTION: We report a patient with multiple myeloma and necrobio-tic xanthogranuloma (NXG) of the skin and liver. After the treatment with bortezomib, lenalidomid and dexamethasone, complete remission was attained after 4 cycles with decrease of monoclonal immunoglobulin to an unmeasurable concentration. At the same time, the dis-appearance of cutaneous and hepatic lesions of NXG on FDG-PET/CT was evident. The administration of bortezomib was stopped after 8 cycles and only continued with lenalidomide as a maintenance therapy. However, after four cycles of this therapy, bilirubin increased above the upper limit and the increase continued till the 11th month of lenadomide administration, when bilirubin reached the highest concentration of 75 μmol/l (more than the three-fold of the upper limit, grade III toxicity). The patient had asymptomatic hyperbilirubinemia with no underlying liver disease or renal impairment while being on lenalidomide therapy. Genetic studies proved mutation; insertion in the promotor gene UGT1A1 typical for Gilbert syndrome. Hyperbilirubinemia may be attributed to the unmasking of previously undia-gnosed Gilbert syndrome. Therefore, the therapy with lenalidomide was interrupted after 11 months. The bilirubin level decreased after the discontinuation of the drug. CONCLUSION: NXG disappeared after fulfilling complete remission of multiple myeloma with disappearance of monoclonal immunoglobulin. This observation supports the hypothesis that monoclonal immunoglobulin has a crucial role in the ethiopathogenesis of NXG and suggests the treatment of monoclonal gammopathy if present in a patient with NXG, hoping that this will result in xantogranuloma disappearance.

Iodine seed localisation of non-palpable lesions in breast surgery first experience.

Surgical therapy of non-palpable malignant breast lesions requires precise preoperative localisation. Recently, radioactive iodine seed localisation has excelled among the number of localisation methods. We present our first experience with this method at our department. We describe the structure of the radioactive iodine seed, the principles of preoperative localisation and peroperative detection of the seed, the specimen transport process, histopathological examination, storage and disposal of the seed, as well as aspects of radiation protection.

IgG4-releated disease.

BACKGROUND: IgG4-related disease (IgG4-RD) is a non-malignant, chronic, immune-related disease. It was first recognized as a distinct disease in 2012 and the first classification criteria were published in 2020. This new entity can cause fibroinflammatory lesions in nearly any organ. It often presents as a multi-organ disease and can be confused with malignancy, infection or other immune-mediated conditions. Although the disease could affect virtually any organ, there are strong predilections for certain organs: the major salivary glands, the orbits and lacrimal glands, the pancreas and biliary tree, the lungs, the kidneys, the aorta and retroperitoneum, the meninges and the thyroid gland. PURPOSE: Correlation among clinical, serologic, radiologic and pathologic data is required for establishing IgG4-RD. We sum up the newest information necessary for the dia-gnosis.

FDG-PET/ CT for initial staging and response assessment in Castleman disease - retrospective single-center study of 29 cases.

BACKGROUND: Castleman disease (CD) is a rare lymphoproliferative disorder including unicentric and multicentric forms which can further be divided into four histopathologic variants (hyaline vascular, plasma cell, mixed, and plasmablastic). Multicentric CD typically behaves as an aggressive, relapsing entity with generalized lymphadenopathy and systemic symptoms. PET/CT following 18F-fluorodeoxyglucose administration (FDG-PET/CT) represents an imaging modality commonly used in malignant lymphomas for staging purposes and response assessment. However, literature data on its role in CD have been limited. PATIENTS AND METHODS: Twenty-nine patients, 18 men and 11 women, dia-gnosed in 1998-2016 were enrolled in our retrospective study. All patients underwent FDG-PET/CT during initial staging and/or as part of response assessment. We measured the maximum diameter of a lesion and established an index value corresponding to the ratio of the maximum standardized uptake value for the observed lesion and for the liver. The information about imaging examinations, patients, and disease extensions was put in a registry and statistically analyzed. RESULTS: Unicentric and multicentric CD was dia-gnosed in 17 and 12 patients, respectively. Median age at the dia-gnosis was comparable between the two groups (51 and 58 years, respectively; P = 0.352). The majority of patients with multicentric CD (83%) were men. In women, the unicentric form prevailed (82 vs. 18%) while the difference between the two forms was of borderline significance in men (44 vs. 56%; P = 0.064). Most of the patients (88%) with unicentric CD had the hyaline vascular pathology type. On the contrary, the plasma cell type was predominant in multicentric CD (42%). The most commonly included anatomic sites included the retroperitoneum (52%) and the thorax (43%). Inguinal node involvement developed only in patients with multicentric CD. In repeatedly examined patients, FDG-PET/CT demonstrated a progressively decreasing size and metabolic activity of a selected lymph node. CONCLUSION: FDG-PET/CT represents a suitable modality for initial staging and response monitoring of CD, especially in patients with a multicentric form.

Diagnostic relevance of 18F-FDG PET/CT in newly diagnosed patients with monoclonal gammopathy of undetermined significance (MGUS): Single-center experience.

Monoclonal gammopathy of undetermined significance (MGUS) is a known precursor of more serious cancers, such as multiple myeloma (MM), Waldenström macroglobulinemia (MW) and other lymphoproliferative disorders. Using 18F-FDG PET/CT, we aimed to evaluate its benefit in early detection of various accompanying disorders and illnesses in MGUS patients. We prospectively analyzed the diagnostic relevance of 18F-FDG PET/CT in 390 newly diagnosed MGUS patients. On 18F-FDG PET/CT scans, the presence of focal or diffuse areas of detectable increased tracer uptake was recorded in 37 (9.5%) MGUS patients. The most frequent pathology was lymphadenopathy (3.8%), followed by thyroid diseases (2.1%), rheumatic diseases (1.8%), and other solid malignancies (1.5%). These results have major implications for confirmed associations of MGUS with numerous malignant and non-malignant disorders. We believe that 18F-FDG PET/CT imaging in newly diagnosed MGUS patients may be useful in early detection of other serious pathologies, not only in predicting progression of MGUS to active MM, and should be strongly recommended if available.

Ablative dose stereotactic body radiation therapy for oligometastatic disease: a prospective single institution study.

Localized, metastasis-directed stereotactic body radiation therapy (SBRT) of oligometastatic disease (OD) is currently rapidly evolving standard of care in many institutions. Further reports of outcomes are required to strengthen the level of evidence in the absence of comparative trials evaluating different practical procedures. The aim of this prospective single institutional study is to analyse, in unselected cohort of patients from real-world clinical practice, the long-term survival, tumor control outcomes and safety of SBRT in OD (radical ablative radiotherapy with biological equivalent dose BED10>100 Gy). In addition to standard toxicity and survival parameters, we report unique outcomes as FFWD - Freedom from widespread dissemination, FFNT - Freedom from the need of subsequent treatment and functional survival with Karnofsky performance status higher than 70%. A total of 110 patients were prospectively evaluated, 60% and 40% were treated for lung and liver oligometastatic disease, respectively. No grade 3 or 4 acute toxicities (CTCAE) were reported. With median follow up of 22.2 months and 2-year overall survival of 88.3%, four patients (6.1%) experienced local progression in the lung SBRT cohort. In the liver SBRT cohort, median follow up was 33 months, 2-year overall survival was 68.5% and 11 patients (25%) experienced local and 36 (81.8%) distal progression. Higher BED10 of 150-170 Gy compared to 100-150 Gy was an independent positive prognostic factor for local progression-free survival for all patients with hazard ratio 0.25. This confirms SBRT ablative radiobiology effects to be independent of OD primary histology and location. The best outcomes in terms of FFNT were observed in the multivariable analysis of patients with 1-2 lung OD compared to both the liver OD cohort and patients with more than 2 lung metastases. Better FFNT in the liver SBRT cohort was observed in patients with 1-2 liver metastases and in patients whose liver OD was irradiated by higher BED10. In conclusion, SBRT is a suitable option for patients who are not surgical candidates; with approximately 30% of patients not requiring subsequent treatment 2 years after SBRT. We believe that this treatment represents a safe and effective option for oligometastatic involvement in patients with various primary tumors.

PET/CT in giant cell arteritis: High 18F-FDG uptake in the temporal, occipital and vertebral arteries / PET/TC en la arteritis de células gigantes: alta acumulación de 18F-FDG en las arterias temporal, occipital y vertebral

18F-FDG PET/CT imaging is useful in patients with fever of unknown origin and can detect giant cell arteritis in extracranial large arteries. However, it is usually assumed that temporal arteries cannot be visualized with a PET/CT scanner due to their small diameter. Three patients with clinical symptoms of temporal arteritis were examined using a standard whole body PET/CT protocol (skull base - mid thighs) followed by a head PET/CT scan using the brain protocol. High 18F-FDG uptake in the aorta and some arterial branches were detected in all 3 patients with the whole body protocol. Using the brain protocol, head imaging led to detection of high 18F-FDG uptake in temporal arteries as well as in their branches (3 patients), in occipital arteries (2 patients) and also in vertebral arteries (3 patients) (AU)

El estudio con 18F-FDG PET/TC es útil en los pacientes con fiebre de origen desconocido y puede detectar la arteritis de células gigantes en las grandes arterias extracraneales. Sin embargo, por lo general se supone que las arterias temporales no pueden ser visualizadas por medio de PET/TC porque su diámetro es pequeño. Se examinó a tres pacientes con arteritis temporal mediante el protocolo PET/TC estándar de cuerpo completo (base del cráneo - mitad del muslo) seguido del protocolo PET/TC de cabeza para cerebro. En los tres pacientes se observó la alta acumulación de 18F-FDG en la aorta y en algunas arterias. Mediante el protocolo para cerebro se observó la intensa acumulación de 18F-FDG en las arterias temporales y sus ramas (3 pacientes), en las arterias occipitales (2 pacientes) y también en las arterias vertebrales (3 pacientes) (AU)

[Current Progresses in Developing PET Radiopharmaceuticals for Patients in the Czech Republic]. / Pokroky ve vývoji PET radiofarmak pro pacienty v Ceské republice.

BACKGROUND: In Masaryk Memorial Cancer Institute (MMCI), there is a long-running intensive joint effort of the RECAMO project and commercial entities, involving mainly clinical evaluations of state-of-the-art PET radiopharmaceuticals leading to their future availability for Czech physicians and their patients. Recently, the PET tracers [11C]methionine and [18F]fluorocholine, among others, were developed in this cooperation, both of them tracers with high importance for oncologic positron emission tomography diagnostics. [11C]methionine, labeled by carbon-11 with a half-life of 20 min, is a proteosynthesis marker used primarily for brain tumor visualization, whereas [18F]fluorocholine, labeled by fluorine-18 with a half-life of 109 min, is a marker of synthesis of cellular membranes and cell proliferation, its primary use being PET diagnostics of prostate carcinoma. AIM: The results of clinical evaluations of both PET radiopharmaceuticals, performed on the basis of parameters agreed and approved beforehand in cooperation of MMCI, RECAMO and the manufacturer of said radiopharmaceuticals, aimed to prove the efficiency and suitability of both compounds for oncologic PET diagnostics for said tumors. In both cases, the radiopharmaceuticals were evaluated in regard to their major use. CONCLUSION: The obtained results prove the benefits and efficiency of both compounds in PET diagnostics of respective tumors. The results, in the form of clinical evaluation reports, will be used as part of the documentation required for marketing authorization of these compounds for use in the Czech Republic.Key words: positron emission tomography - radiopharmaceuticals - L-methyl-11C-methionine - 18F-fluorocholineThis work was supported by the project MEYS - NPS I - LO1413.The authors declare they have no potential conflicts of interest concerning drugs, products, or services used in the study.The Editorial Board declares that the manuscript met the ICMJE recommendation for biomedical papers.Submitted: 10. 6. 2016Accepted: 17. 6. 2016.

[Localized Amyloidosis Involving the Nasal Cavity]. / Lozisková amyloidóza v dutine nosní.

BACKGROUND: Amyloidosis is a disease characterized by deposits of abnormal protein known as amyloid in various organs and tissues. It can be classified into systemic or localized forms, the latter of which is less frequent. Deposition of amyloidogenic monoclonal light chains leads to the most common type of this disease called light-chain (AL) amyloidosis. (18)F-FDG positron emission tomography/ computed tomography hybrid imaging (FDG-PET/ CT) demonstrates tracer uptake usually in all patients with localized amyloidosis as opposed to the systemic form. CASE: Herein, we present a case of an otherwise healthy 56-year-old women diagnosed with a nasal polyp on the right side. The biopsy results were consistent with amyloidosis. FDG-PET/ CT imaging revealed a pathological, metabolically active lesion measuring 11 × 9 mm with a maximum standardized uptake value (SUV(max)) of 3.47. No other distant pathological changes were identified. After a radical resection, the patient has been regularly followed-up with clinical and imaging methods (MRI, FDG-PET/ CT), both of which repeatedly showed normal findings with disease-free survival of 27 months. Thus, FDG-PET/ CT imaging plays an important role not only for obtaining the right diagnosis but also in the follow-up of patients after surgical resection. In accordance with the literature, this case report confirms that FDG-PET/ CT imaging holds promise as an auxiliary method for distinguishing between localized and systemic forms of amyloidosis.

PET/CT in giant cell arteritis: High 18F-FDG uptake in the temporal, occipital and vertebral arteries.

18F-FDG PET/CT imaging is useful in patients with fever of unknown origin and can detect giant cell arteritis in extracranial large arteries. However, it is usually assumed that temporal arteries cannot be visualized with a PET/CT scanner due to their small diameter. Three patients with clinical symptoms of temporal arteritis were examined using a standard whole body PET/CT protocol (skull base - mid thighs) followed by a head PET/CT scan using the brain protocol. High 18F-FDG uptake in the aorta and some arterial branches were detected in all 3 patients with the whole body protocol. Using the brain protocol, head imaging led to detection of high 18F-FDG uptake in temporal arteries as well as in their branches (3 patients), in occipital arteries (2 patients) and also in vertebral arteries (3 patients).

Castlemans disease - surgical treatment, case reports.

The authors describe their experience with surgical treatment of benign rare lymph proliferation - Castlemans disease (CD). It occurs in unicentric and multicentric forms. The very low incidence of the disease makes it very difficult to design larger prospective studies. Cases of two leading localizations of the unicentric form of CD - intrathoracic and retroperitoneal with special emphasis on the preoperative diagnosis and imaging options are described. This article underlines the curative potential of surgical treatment where a complete resection of the affected lymph node leads to eradication in almost 100% of the cases. The discussion is focused on the forms of CD - different localization, clinical symptoms and course of disease. It discusses the differential diagnosis, particularly difficult in the multicentric form, emphasizing the need to exclude malignant lymphoma. The etiopathogenesis of the disease is presented, mentioning its association with HIV (Human Immunodeficiency Virus) infection and HHV-8 (Human herpers virus 8) infection and the importance of overproduction of proinflammatory cytokines. The importance of surgical therapy for the unicentric form of CD is highlighted as compared to the multicentric form, where the surgeon´s task involves taking a biopsy - required for an accurate diagnosis.Key words: Castlemans disease - lymphoproliferation - lymphadenopathy - surgical treatment.

[Failed preoperative lymphoscintigraphy for sentinel lymph node biopsy in breast cancer, possible causes and implications for the surgery - the analysis of 3014 procedures]. / Neúspesná lymfoscintigrafie pred sentinelovou biopsií u karcinomu prsu, mozné príciny a dusledky pro chirurgický výkon - analýza výsledku 3014 vysetrení

INTRODUCTION: The aim of the study was to review the cases of sentinel lymph node biopsy for breast cancer in which preoperative lymphoscintigraphy had shown no axillary hot spot; to assess the frequency of failed examinations and possible causes of the failure; to analyze subsequent surgical procedures and hence to provide a general recommendation on what to do in such a situation. METHODS: A retrospective overview of 3014 lymphoscintigraphy examinations at the Masaryk Memorial Cancer Institute from 2001 to 2011 with a more detailed analysis of the cases with axillary hot spot visualization failure. RESULTS: The axillary hot spot was not shown in 71 examinations (2.4%). The frequency of failed lymphoscintigraphy during the time period did not change substantially. The possible risk factors of failed lymphoscintigraphy include: previous surgery on the breast or the axilla, obturation of the lymphatic drainage with the cancer, and the absence of the tracer injection site massage. The most common surgical procedures to respond to a failed examination were: the application of patent blue and surgical exploration of the axilla, no axillary surgery, or axillary dissection. CONCLUSION: When repeated scanning with the gamma camera through the first several hours is performed, the frequency of failed lymphoscintigraphy procedures remains very low (2.4%). If there is no axillary hot spot shown, patent blue is to be injected and the axilla should be surgically explored. This solution will be successful in most patients. If the sentinel lymph node cannot be detected even using the combined method, the surgical procedure needs to be selected with regard to the individual clinical context.Key words: breast cancer - sentinel lymph node - sentinel lymph node biopsy - lymphoscintigraphy - failed detection.

Pseudogymnoascus destructans: evidence of virulent skin invasion for bats under natural conditions, Europe.

While Pseudogymnoascus destructans has been responsible for mass bat mortalities from white-nose syndrome (WNS) in North America, its virulence in Europe has been questioned. To shed the light on the issue of host-pathogen interaction between European bats and P. destructans, we examined seventeen bats emerging from the fungus-positive underground hibernacula in the Czech Republic during early spring 2013. Dual wing-membrane biopsies were taken from Barbastella barbastellus (1), Myotis daubentonii (1), Myotis emarginatus (1), Myotis myotis (11), Myotis nattereri (1) and Plecotus auritus (2) for standard histopathology and transmission electron microscopy. Non-lethal collection of suspected WNS lesions was guided by trans-illumination of the wing membranes with ultraviolet light. All bats selected for the present study were PCR-positive for P. destructans and showed microscopic findings consistent with the histopathological criteria for WNS diagnosis. Ultramicroscopy revealed oedema of the connective tissue and derangement of the fibroblasts and elastic fibres associated with skin invasion by P. destructans. Extensive fungal infection induced a marked inflammatory infiltration by neutrophils at the interface between the damaged part of the wing membrane replaced by the fungus and membrane tissue not yet invaded by the pathogen. There was no sign of keratinolytic activity in the stratum corneum. Here, we show that lesions pathognomonic for WNS are common in European bats and may also include overwhelming full-thickness fungal growth through the wing membrane equal in severity to reports from North America. Inter-continental differences in the outcome of WNS in bats in terms of morbidity/mortality may therefore not be due to differences in the pathogen itself.

Successful use of metronomic vinblastine and fluorothymidine pet imaging for the management of intramedullary spinal cord anaplastic oligoastrocytoma in a child.

BACKGROUND: Children with high-grade glioma still have a poor prognosis despite the use of multimodal therapy including surgery, radiotherapy, and chemotherapy. New therapeutic strategies and methods evaluating such therapies are needed. OBSERVATION: Here we describe a child with anaplastic oligodendroglioma of the spinal cord who was unable to tolerate standard chemoradiotherapy and who had still-vital residual tumour during therapy. A good response was obtained with low-dose metronomic treatment containing vinblastine. The treatment was guided according to gradual response assessed using various positron-emission tomography tracers. CONCLUSIONS: Metronomic treatment guided by positron-emission tomography could be a reasonable option in some high-risk pediatric tumours.