Franziska Walter

18F-FDG PET/CT for Monitoring Treatment Responses to the Epidermal Growth Factor Receptor Inhibitor Erlotinib

Response rates of unselected non–small cell lung cancer (NSCLC) patients to the epidermal growth factor receptor inhibitor erlotinib are low and range from 10% to 20%. Early response assessments are needed to avoid costs and side effects of inefficient treatments. Here we determined whether early changes in tumor uptake of 18F-FDG can predict progression-free and overall survival in NSCLC patients who are treated with erlotinib. Methods: Twenty-two patients (6 men, 16 women; mean age ± SD, 64 ± 13 y) with stage III or stage IV NSCLC who received erlotinib treatment were enrolled prospectively. 18F-FDG PET/CT was performed before the initiation of treatment (n = 22), after 2 wk (n = 22), and after 78 ± 21 d (n = 11). Tumor maximum standardized uptake values were measured for a maximum of 5 lesions for each patient. Tumor responses were classified using modified PET Response Criteria in Solid Tumors (use of maximum standardized uptake values). Median overall survival by Kaplan–Meier analysis was compared between groups using a log-rank test. Results: The overall median time to progression was 52 d (95% confidence interval, 47–57 d). The overall median survival time was 131 d (95% confidence interval, 0–351 d). Patients with progressive metabolic disease on early follow-up PET showed a significantly shorter time to progression (47 vs. 119 d; P < 0.001) and overall survival (87 vs. 828 d; P = 0.01) than patients classified as having stable metabolic disease or partial or complete metabolic response. Conclusion: These data suggest that 18F-FDG PET/CT performed early after the start of erlotinib treatment can help to identify patients who benefit from this targeted therapy.

Impact of 3,4-Dihydroxy-6-18F-Fluoro-l-Phenylalanine PET/CT on Managing Patients with Brain Tumors: The Referring Physician's Perspective

We investigated the impact of 18F-DOPA brain PET/CT on the clinical management of patients with known or suspected brain tumors. Methods: A prospective survey of referring physicians was conducted. A pre-PET questionnaire inquired about indication, tumor histology or grade, level of suspicion for tumor recurrence, and planned management. Early post-PET questionnaires asked referring physicians to categorize PET findings as negative, equivocal, or positive; assessed the level of suspicion for primary or recurrent brain tumor; and recorded intended management changes prompted by PET findings. A late follow-up questionnaire 6 mo after the scan aimed at determining patient outcome (recurrence, survival). In addition, all referring physicians were contacted to determine whether management changes intended after 18F-DOPA PET/CT were implemented. Results: Fifty-eight consecutive patients were included. The clinical suspicion for recurrence increased in 33%, remained unchanged in 50%, and decreased in 17% of patients after adding the PET/CT result to the available diagnostic data. The late post-PET questionnaire confirmed recurrence in 26 patients whereas 32 had stable disease or remained disease-free. 18F-DOPA PET/CT resulted in intended management changes in 41% of patients. Changes in intended management from wait and watch to chemotherapy (6 patients [25%]) and from chemotherapy to wait and watch (4 patients [17%]) occurred most frequently. Clinical follow-up revealed that 75% of intended treatment changes were implemented. Conclusion: 18F-DOPA PET/CT changed the intended management of 41% of patients with brain tumors, and intended management changes were implemented in 75% of these. These changes suggest a potentially important clinical role of imaging amino acid transport in the management of brain tumor patients.

Is there a need for dedicated bone imaging in addition to 18F-FDG PET/CT imaging in pediatric sarcoma patients?

Purpose: Many children with sarcomas undergo whole body 2-deoxy-2-(18F)fluoro-D-glucose positron emission tomography/computed tomography (18F-FDG PET/CT) and technetium methylene diphosphonate (99Tc-MDP) studies. It is unknown whether the combination of both tests results in more accurate detection of bone lesions than 18F-FDG- PET/CT alone. Methods: 99Tc-MDP bone and 18F-FDG PET/CT scans were each read by 2 “blinded” observers and then reviewed side-by-side by 3 readers. Bone lesions were graded qualitatively on a 5-point scale (from benign to malignant). Clinical and imaging follow-up (n=21) and bone biopsy results (n=8) served as reference standard. Results: A total of 39 paired 99Tc-MDP and 18F-FDG-PET/CT studies (cases) performed at a mean interval 4±7 days, were performed on 29 patients (mean age 12±5 y). Of these, 21 patients (72%) had bone sarcoma, whereas 8 patients (28%) had soft tissue sarcoma. By patient and case-based analysis, 18F-FDG PET/CT had an accuracy of 100%. 99Tc-MDP had accuracies of 90% and 82% by patient and case-based analysis. The combined interpretation had an accuracy of 97%. Conclusions: In this study, 99Tc-MDP bone imaging does not provide an added diagnostic value for bone involvement over 18F-FDG-PET/CT.

18F-FluoroDeoxyGlucose Uptake of Bone and Soft Tissue Sarcomas in Pediatric Patients

A high 18F-fluorodeoxyglucose (FDG) uptake by positron emission tomography/computed tomography (PET/CT) imaging in sarcomas of adults has been reported. The current study aimed at defining the degree of 18F-FDG uptake of pediatric sarcomas. This retrospective study included 29 patients (23 males, 6 females; mean age 14 ± 5 years) with soft tissue (n = 9) or bone (n = 20) sarcomas. Twenty-two patients (76%) underwent 18F-FDG PET/CT and 7 (24%) had dedicated 18F-FDG PET studies. Tumor 18F-FDG uptake was quantified by standard uptake value (SUV)max and tumor-to-liver ratios (SUV ratios; tumor SUVmax/liver SUVmean). Tumor SUVmax and SUV ratios were correlated with tumor Ki-67 expression. SUVmax ranged from 1.4 to 24 g/mL (median 2.5 g/mL) in soft tissue sarcomas and 1.6 to 20.4 g/mL (median 6.9 g/mL) in bone sarcomas (P = .03), and from 1.6 to 9.2 g/mL (median 3.9 g/mL) and 3.5 to 20.4 g/mL (median 12 g/mL) in Ewing sarcoma and osteosarcoma, respectively (P = .009). Tumor SUV ratios ranged from 0.8 to 8.7 (median 1.9) in soft tissue sarcomas and 1.4 to 8.9 (median 3.8) in bone sarcomas (P = .08). Ewing sarcoma had a significantly lower tumor SUV ratio than osteosarcoma (P = .01). Ki-67 expression correlated significantly with the 18F-FDG uptake in bone but not in soft tissue sarcomas. All sarcomas were visualized by 18F-FDG PET/CT imaging. A higher 18F-FDG uptake was observed in osteosarcoma than in Ewing and soft tissue sarcomas. The results of this study suggest that the degree of tumor 18F-FDG uptake is sufficient to allow for monitoring of therapeutic responses in pediatric sarcomas.