Role of FDG-PET in the implementation of involved-node radiation therapy for Hodgkin lymphoma patients.

PURPOSE: This study examines the role of (18)F-labeled fluorodeoxyglucose positron emission tomography (FDG-PET) in the implementation of involved-node radiation therapy (INRT) in patients treated for clinical stages (CS) I/II supradiaphragmatic Hodgkin lymphoma (HL). METHODS AND MATERIAL: Patients with untreated CS I/II HL enrolled in the randomized EORTC/LYSA/FIL Intergroup H10 trial and participating in a real-time prospective quality assurance program were prospectively included in this study. Data were electronically obtained from 18 French cancer centers. All patients underwent APET-computed tomography (PET-CT) and a post-chemotherapy planning CT scanning. The pre-chemotherapy gross tumor volume (GTV) and the postchemotherapy clinical target volume (CTV) were first delineated on CT only by the radiation oncologist. The planning PET was then co-registered, and the delineated volumes were jointly analyzed by the radiation oncologist and the nuclear medicine physician. Lymph nodes undetected on CT but FDG-avid were recorded, and the previously determined GTV and CTV were modified according to FDG-PET results. RESULTS: From March 2007 to February 2010, 135 patients were included in the study. PET-CT identified at least 1 additional FDG-avid lymph node in 95 of 135 patients (70.4%; 95% confidence interval [CI]: 61.9%-77.9%) and 1 additional lymph node area in 55 of 135 patients (40.7%; 95% CI: 32.4%-49.5%). The mean increases in the GTV and CTV were 8.8% and 7.1%, respectively. The systematic addition of PET to CT led to a CTV increase in 60% of the patients. CONCLUSIONS: Pre-chemotherapy FDG-PET leads to significantly better INRT delineation without necessarily increasing radiation volumes.

Postradioiodine treatment whole-body scan in the era of 18-fluorodeoxyglucose positron emission tomography for differentiated thyroid carcinoma with elevated serum thyroglobulin levels.

BACKGROUND: Patients with differentiated thyroid cancer (DTC) who have a suspicious recurrent or persistent disease based on an elevated serum thyroglobulin (Tg) or Tg antibodies (TgAb) are usually referred for empiric radioiodine ((131)I) administration to localize and treat the disease. The aim of this retrospective monocentric study was to assess the sensitivity of postempiric (131)I whole-body scan (WBS) compared to 18-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) in such patients who had an initial normal postablation WBS. METHODS: Among 47 consecutive patients with DTC who had a normal postablation WBS and were referred for empiric (131)I administration, 34 patients (12M, 22F; mean age 53 years) underwent FDG PET/CT and form the basis of this report: 23 patients had persistently elevated serum Tg levels, 10 had elevated Tg levels observed during follow-up after they initially became under 1 ng/mL, and 1 had appearance of TgAb during follow-up. Postempiric (131)I WBS and FDG PET/CT were analyzed by independent readers. RESULTS: A total of 75 lesions were found in 23 patients, distributed in 36 organs. Lesions were located in the neck (30), lungs (28), mediastinum (11), and bones (6). The sensitivities for the detection of individual lesions and for the diagnosis of metastatic organs were 88% and 97% for PET/CT and 16% and 22% for WBS, respectively (p<0.01). PET/CT was abnormal in 22 patients, among which 5 also had an abnormal postempiric (131)I WBS. There was only one patient with an abnormal postempiric (131)I WBS and a normal FDG PET/CT. This patient underwent two further (131)I administrations, with the last WBS being normal and the last stimulated Tg level being undetectable. Other patients were either treated with surgery, or classified as radioactive iodine refractory and treated with levothyroxine suppressive therapy or tyrosine kinase inhibitors. CONCLUSION: In patients with suspicious recurrence based on the Tg level after a normal postablation WBS, FDG PET/CT is the preferred scintigraphic method to localize disease rather than postempiric (131)I WBS. Empiric (131)I administration may be used only in patients who do not have a significant FDG uptake.