Is PET/CT necessary in paediatric oncology?

EANM consensus document on the use of [18F]FDG PET/CT in fever and inflammation of unknown origin

PURPOSE

Patients with fever and inflammation of unknown origin (FUO/IUO) are clinically challenging due to variable clinical presentations with nonspecific symptoms and many differential diagnoses. Positron emission tomography/computed tomography (PET/CT) with 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG) is increasingly used in FUO and IUO, but the optimal diagnostic strategy remains controversial. This consensus document aims to assist clinicians and nuclear medicine specialists in the appropriate use of [18F]FDG-PET/CT in FUO and IUO based on current evidence.

METHODS

A working group created by the EANM infection and inflammation committee performed a systematic literature search based on PICOs with "patients with FUO/IUO" as population, "[18F]FDG-PET/CT" as intervention, and several outcomes including pre-scan characteristics, scan protocol, diagnostic yield, impact on management, prognosis, and cost-effectiveness.

RESULTS

We included 68 articles published from 2001 to 2023: 9 systematic reviews, 49 original papers on general adult populations, and 10 original papers on specific populations. All papers were analysed and included in the evidence-based recommendations.

CONCLUSION

FUO and IUO remains a clinical challenge and [18F]FDG PET/CT has a definite role in the diagnostic pathway with an overall diagnostic yield or helpfulness in 50-60% of patients. A positive scan is often contributory by directly guiding treatment or subsequent diagnostic procedure. However, a negative scan may be equally important by excluding focal disease and predicting a favorable prognosis. Similar results are obtained in specific populations such as ICU-patients, children and HIV-patients.

Use of PET/CT instead of CT-only when planning for radiation therapy does not notably increase life years lost in children being treated for cancer

BACKGROUND

PET/CT may be more helpful than CT alone for radiation therapy planning, but the added risk due to higher doses of ionizing radiation is unknown.

OBJECTIVE

To estimate the risk of cancer induction and mortality attributable to the [F-18]2-fluoro-2-deoxyglucose (FDG) PET and CT scans used for radiation therapy planning in children with cancer, and compare to the risks attributable to the cancer treatment.

MATERIALS AND METHODS

Organ doses and effective doses were estimated for 40 children (2-18 years old) who had been scanned using PET/CT as part of radiation therapy planning. The risk of inducing secondary cancer was estimated using the models in BEIR VII. The prognosis of an induced cancer was taken into account and the reduction in life expectancy, in terms of life years lost, was estimated for the diagnostics and compared to the life years lost attributable to the therapy. Multivariate linear regression was performed to find predictors for a high contribution to life years lost from the radiation therapy planning diagnostics.

RESULTS

The mean contribution from PET to the effective dose from one PET/CT scan was 24% (range: 7-64%). The average proportion of life years lost attributable to the nuclear medicine dose component from one PET/CT scan was 15% (range: 3-41%). The ratio of life years lost from the radiation therapy planning PET/CT scans and that of the cancer treatment was on average 0.02 (range: 0.01-0.09). Female gender was associated with increased life years lost from the scans (P < 0.001).

CONCLUSION

Using FDG-PET/CT instead of CT only when defining the target volumes for radiation therapy of children with cancer does not notably increase the number of life years lost attributable to diagnostic examinations.

Noninvasive assessment of pediatric inflammatory bowel disease with ¹⁸F-fluorodeoxyglucose-positron emission tomography and computed tomography

OBJECTIVES

¹⁸F-fluorodeoxyglucose (FDG)-positron emission tomography (PET) is a less invasive diagnostic tool and promising in detecting gastrointestinal lesions of pediatric inflammatory bowel disease (IBD) patients. Co-registration of low-dose computed tomography (CT) could lead to improvements in the assessment of disease. Therefore, this retrospective study evaluates the value of PET±CT in pediatric IBD patients.

PATIENTS AND METHODS

We analyzed ¹⁸F-FDG-PET scans without (n=24) or with combined (n=21) low-dose CT in children (18 females, 27 males, age: 3.7-16.7 years, median 13.2 years) who presented with the diagnosis of IBD (n=45). Results of PET±CT scans and conventional diagnostic procedures (endoscopy, histology, and ultrasound) were compared by a segment-based analysis.

RESULTS

Overall, 253 segments of the gastrointestinal tract (GIT) were explored by endoscopy/histology and ¹⁸F-FDG-PET±CT. Twenty-five additional small bowel segments were assessed by abdominal ultrasound and further 152 GIT segments not reached during endoscopy were evaluated by PET±CT. PET±CT revealed a segment-based sensitivity, specificity, positive predictive value, negative predictive value, and an accuracy for the detection of GIT lesions of 82, 97, 96, 88, and 91%, respectively. The patient-based sensitivity and specificity was 97 and 100%, respectively. Interestingly, the co-registration of CT did not improve the diagnostic informative value.

CONCLUSION

FDG-PET±CT is especially suitable for the assessment of IBD in children. The radiation exposure of 3-7 mSv is justified by the accuracy of this approach. FDG-PET seems to be a reliable tool for detecting inflamed gut segments in IBD with high sensitivity and specificity. The co-registration of CT had no additional benefit.

Guidelines for 18F-FDG PET and PET-CT imaging in paediatric oncology

OBJECTIVE

The purpose of these guidelines is to offer to the nuclear medicine team a framework that could prove helpful in daily practice. These guidelines contain information related to the indications, acquisition, processing and interpretation of (18)F-fluorodeoxyglucose positron emission tomography ((18)F-FDG PET) in paediatric oncology. The Oncology Committee of the European Association of Nuclear Medicine (EANM) has published excellent procedure guidelines on tumour imaging with (18)F-FDG PET (Bombardieri et al., Eur J Nucl Med Mol Imaging 30:BP115-24, 2003). These guidelines, published by the EANM Paediatric Committee, do not intend to compete with the existing guidelines, but rather aim at providing additional information on issues particularly relevant to PET imaging of children with cancer.

CONCLUSION

The guidelines summarize the views of the Paediatric Committee of the European Association of Nuclear Medicine. They should be taken in the context of "good practice" of nuclear medicine and of any national rules, which may apply to nuclear medicine examinations. The recommendations of these guidelines cannot be applied to all patients in all practice settings. The guidelines should not be deemed inclusive of all proper procedures or exclusive of other procedures reasonably directed to obtaining the same results.

F-18 FDG PET in Infectious Diseases in Children

PURPOSE

The aim is to report our observations regarding the role of F-18 FDG PET in children's infectious processes.

MATERIAL AND METHODS

A presentation is made of 3 neonatal infections unresponsive to treatment, 2 invasive infections in immunocompromised children, and 1 discitis in an immunocompetent child. PET or PET/CT was performed to address a specific question pertaining to the management of the diseases. Results were correlated with the clinical outcome. The impact on patient management is discussed.

RESULTS

In 1 neonate, PET localized the infection in a bone which allowed surgical curettage. In another one, it localized the infection in recently renewed exogenous material and led to subsequent removal. It was negative in the third one, whose evolution was rapidly favorable. In the immunocompromised children, treatment of invasive infection was adapted according to the metabolic inflammatory activity of the disease. In a limping child with slight abnormalities on bone scintigraphy but major misleading involvement on MRI, PET/CT demonstrated hypermetabolism limited to a disc, thus avoiding further invasive procedures.

CONCLUSIONS

Although not meant as a first choice examination, F-18 FDG PET should be considered in difficult cases of neonatal infection or in challenging diagnoses like discitis in the young child. It provides more accurate staging and treatment monitoring of the inflammatory process in invasive infections of immunocompromised children.