الفهرس | Only 14 pages are availabe for public view |
Abstract Studying the impact of different imaging approaches on the accuracy of staging, monitoring response, prognosis and detection of early relapse in children suffering from HL is mandatory to achieve better therapy and better prognosis in such age group. Positron emission tomography using 18F-fluoro-deoxy-glucose (FDG-PET) is considered an excellent tool for staging and monitoring disease status in patients with lymphoma. In our study, 53.7% of patients showed discrepant findings between PET and conventional imaging modalities. Nevertheless, therapy was modified in only 20.4% of patients according to the change in their stage. FDG-PET modified therapy in 7/54 patients (about 13%) and CIMs modified therapy in 4/54 patients (about 7%). This study was planned to assess the effectiveness of 18F-FDG PET performed before starting therapy (staging PET or PET1) and early after two cycles of chemotherapy (interim PET or PET2) in pHL patients emphasizing on in their different pathological subgroups. Different risk factors and therapy groups were also tested for their correlation to the patients’ outcome. Only bone marrow infiltration was significantly related to the patient’s outcome (p value = 0.0007). Different visual and semiquantitative techniques were used to evaluate their potential prognostic role to assess response to therapy measured from staging, interim PET, and the combined results of both PETs. A comparison of different PET data analyses was performed applying individualized standardized uptake values (SUV), PET-derived metabolic tumor volume (MTV), and the product of both parameters, termed total lesion glycolysis (TLG). One-hundred-eight PET datasets (PET1, n=54; PET2, n=54) of 54 children were analysed by visual and semi-quantitative means. SUVmax, SUVmean, MTV, and TLG were obtained. Results of both PETs and the relative change from PET1 to PET2 (Δ in %) were compared for their capability of identifying responders and non-responders using receiver operating characteristics (ROC)- curves. All semi-quantitative SUV estimates obtained at PET2 were significantly superior to the visual PET2 analysis. However, ΔSUVmax revealed the best results (area under the curve, 0.92; P<0.001; sensitivity 100%; specificity 85.4%; PPV 46.2%; NPV 100%; accuracy, 87.0%) but was not significantly superior to SUVmax-estimation at PET2 and ΔTLGmax. In summary, elaborated techniques of semi-quantitative reading of FDG-PET data for early response-to-therapy assessment in pHL such as SUV correction for body surface area or metabolically guided volumetric analyses (e.g., MTV, TLG) fail to improve the PPV to a clinically acceptable minimum of at least 80% while preserving maximum NPV. Instead, SUVmax estimation of the interim PET or— in order to increase the PPV—the ΔSUVmax from the staging PET to the interim PET demonstrate equivalent results whereas their calculation is much faster in aclinical setting. We may conclude that the high rate of false positive cases is not necessarily aweakness of FDG PET but in turn is owed to the strength of the optimized subsequent treatment and the disproportional time points of treatment success estimation: after two cycles of chemotherapy in case of PET2 against full course of chemo-/ radio-chemotherapy in case of outcome estimation. Considering this, a positive interim PET2 is not an optimal base to draw a treatment escalation decision from, e.g. adding or omitting radiotherapy, respectively. from a clinical point of view the high NPV provides an option to avoid radiotherapy in interim PET-negative pHL patients regardless of their initially attributed disease-related risk. Recommendations: Prospective patient collection with larger sample size and longer follow up periods are recommended to validate the predictive value of negative interim PET along years of close follow up. Larger sample sizes are needed to draw valuable results regarding different pathological subgroups of paediatric HL and to get deeper insight about the characteristics of each pathological subtype. A multidisciplinary tumor board is necessary for better reading of the results of patients’ clinical data along with the findings of all conventional imaging modalities (CIM) side by side with FDG-PET/CT in pediatric lymphomas. A team should include pediatric hematologists, diagnostic radiologists, nuclear medicine physicians, and radiation oncologists. Sstandardized and reproducible methods for PET scanning and reporting should be respected as guidelines between PET/CT centers for standardization of the results visual or semiquantitative analysis techniques. More sophisticated semi-quantitative techniques should not replace the simple and fast analytical measures like SUVmax. Meanwhile, built in calculation algorithms of the best performing semiquantitative measures should be provided by the commercial workstations and analytical programs used for display and quantification of PET/CT studies to achieve more accurate prediction of the patient’s outcome and hence achieve better prognosis. Negative PET2 provides an option to omit radiotherapy regardless of patient initial staging. Meanwhile, a positive PET2 is not an optimal base to add radiotherapy, but indicates the need for additional investigation by molecular imaging using new tracers such as: 11C-methionine 18F fluorothymidine (FLT). |