The role of FDG-PET/CT in the evaluation of residual disease in paediatric non-Hodgkin lymphoma

Abstract

(18) F-labelled-fluorodeoxyglucose positron emission tomography (FDG-PET) findings are challenging to interpret for residual disease versus complete response in paediatric patients with non-Hodgkin lymphoma (NHL). A biopsy is often warranted to confirm the presence or absence of viable tumour if there is clinical or radiographic evidence of residual disease. In this study, we compared conventional imaging and FDG-PET/computerized tomography (CT) findings with biopsy results in 18 children with NHL. Our goal was to provide additional data to establish more reliable criteria for response evaluation. Residual disease was suspected after conventional imaging alone in eight patients, after FDG-PET/CT alone in three and after both modalities in seven patients. Biopsy confirmed the presence of viable tumour in two patients. Two additional patients experienced progressive disease or relapse. The sensitivity and negative predictive value of FDG-PET/CT using the London criteria to indicate residual tumour detectable by biopsy were 100%, but specificity was low (60%), as was the positive predictive value (25%). Thus, in this study, a negative FDG-PET/CT finding was a good indicator of complete remission. However, because false-positive FDG-PET/CT findings are common, biopsy and close monitoring are required for accurate determination of residual disease in individual patients.

Keywords: biopsy; neoplasm; non-Hodgkin lymphoma; positron-emission tomography; residual.

© 2014 John Wiley & Sons Ltd.

Figures

Figure 1. Correlation of imaging and biopsy findings

Findings of conventional imaging, FDG-PET/CT and biopsy for individual patients are indicated in the figure. Four of 9 patients with FDG-PET/CT findings suggestive of residual disease developed progressive disease or relapse, 2 of whom had negative biopsies at the time of response evaluation. +, positive result; -, negative result; ±, indeterminate result *FDG-PET/CT for Patient 18 was reported to be positive at the time of response evaluation, but negative at the time of retrospective review for this study. FDG-PET/CT, 18F-labelled–fluorodeoxyglucose positron emission tomography with computerized tomography; PD, progressive disease.

Figure 2. True-negative FDG-PET/CT study

Patient 12 (13-year-old boy treated for diffuse large B-cell lymphoma). A) Conventional abdominal computerized tomography (CT) shows a residual retroperitoneal mass that measured 7.1 × 5.3 cm. (arrows). B) Axial and C) coronal 18F-labelled–fluorodeoxyglucose positron emission tomography with computerized tomography (FDG-PET/CT) images show the mass to be non-FDG avid (arrows). The mass was negative for viable tumour on histopathological inspection.

Figure 2. True-negative FDG-PET/CT study

Patient 12 (13-year-old boy treated for diffuse large B-cell lymphoma). A) Conventional abdominal computerized tomography (CT) shows a residual retroperitoneal mass that measured 7.1 × 5.3 cm. (arrows). B) Axial and C) coronal 18F-labelled–fluorodeoxyglucose positron emission tomography with computerized tomography (FDG-PET/CT) images show the mass to be non-FDG avid (arrows). The mass was negative for viable tumour on histopathological inspection.

Figure 2. True-negative FDG-PET/CT study

Patient 12 (13-year-old boy treated for diffuse large B-cell lymphoma). A) Conventional abdominal computerized tomography (CT) shows a residual retroperitoneal mass that measured 7.1 × 5.3 cm. (arrows). B) Axial and C) coronal 18F-labelled–fluorodeoxyglucose positron emission tomography with computerized tomography (FDG-PET/CT) images show the mass to be non-FDG avid (arrows). The mass was negative for viable tumour on histopathological inspection.

Figure 3. False-positive FDG-PET/CT study

Patient 6 (20-year-old young man treated for Burkitt lymphoma. A) Diagnostic pelvic computerized tomography (CT) shows a residual pelvis mass (arrows). B) Axial positron emission tomography (PET)/CT shows the mass to have intense peripheral fluorodeoxyglucose avidity (arrow). The mass was resected and found to contain necroinflammatory tissue but no viable tumour on histopathological examination.

Figure 3. False-positive FDG-PET/CT study

Patient 6 (20-year-old young man treated for Burkitt lymphoma. A) Diagnostic pelvic computerized tomography (CT) shows a residual pelvis mass (arrows). B) Axial positron emission tomography (PET)/CT shows the mass to have intense peripheral fluorodeoxyglucose avidity (arrow). The mass was resected and found to contain necroinflammatory tissue but no viable tumour on histopathological examination.