Evaluation of integrated whole-body PET/CT in the detection of recurrent ovarian cancer
Introduction
Current treatment trends for patients with ovarian cancer include initial surgical staging with aggressive tumour debulking followed by multidrug chemotherapy [1]. Because of the relatively high incidence of ovarian cancer recurrence, clinical follow-up is essential [2]. Measurement of tumour markers, chiefly CA 125, has been used for follow-up, but a normal CA 125 level does by no means rule out disease [3]. Recent advances in diagnostic imaging, in particular helical CT and contrast-enhanced MR imaging, have improved re-staging in the setting of recurrent ovarian cancer [4], [5], [6], [7]. Early diagnosis of tumour recurrence may, however, fail in cases with small, disseminated lesions and even detectable tumours cannot always be definitely diagnosed as recurrence [4].
Positron emission tomography (PET) with 2-[18F]-fluoro-2-deoxy-d-glucose (FDG) has evolved as a useful technique in clinical oncology, especially for tumour staging and post-treatment monitoring [2], [8], [9], [10], [11], [12], [13]. It provides metabolic information and may help detect small metastatic lesions. Due to its relative scarcity of anatomic landmarks, however, stand-alone PET imaging remains frequently unsatisfactory [12].
This major limitation of PET imaging is overcome by the availability of integrated whole-body PET/CT imaging systems. PET and CT images are acquired in an integrated procedure, yielding intrinsically fused morphological and functional data sets [14], [15]. Initial studies with this combined technique have shown promising results [16], [17], [18], [19], [20].
The purpose of this prospective study was to determine the accuracy of integrated whole-body PET/CT imaging in detecting recurrent ovarian cancer when compared with PET alone and CT alone.
Section snippets
Material and methods
PET/CT imaging was performed in 19 patients with a history of surgically resected ovarian cancer and suspected tumour recurrence (age range, 49–80 years; mean age, 67 years). The International Federation of Gynecology and Obstetrics (FIGO) tumour stage at initial diagnosis was stage II in 3, stage III in 13 and stage IV in 3 patients. The time interval between initial diagnosis and PET/CT examination varied between 6 months and 4 years (median, 12 months). The study was conducted in full
PET/CT imaging
Combined PET/CT imaging was conducted on a biograph™ (Siemens Medical Solutions, Hoffman Estates, USA). CT imaging was accomplished with a dual-slice helical CT based on a Somatom Emotion (Siemens Medical Solutions, Erlangen, Germany), while PET data were collected with a full-ring PET tomograph based on an ECAT EXACT HR+ (Siemens Medical Solutions). The PET component has an in-plane spatial resolution of 4.6 mm and an axial field of view of 15.5 cm for one bed position. The system provides
Image evaluation
All data sets were analysed on a workstation capable of interactively providing multiplanar reformations and any desirable window/level setting.
PET data sets were evaluated by two nuclear medicine physicians in consensus, while CT data sets were evaluated by two radiologists in consensus. PET/CT images were evaluated by the same nuclear medicine physicians and radiologists in consensus.
Localisations of recurrence were classified as one of local tumour recurrence, pelvic lymph node metastases,
Standard of reference
In 5 of the 11 patients with recurrent disease, pathological findings at second-look surgery served as the standard of reference. In all other patients of this study, clinical follow-up was conducted after completion of the required 6-month period to provide the standard of reference. It comprised all available clinical data, including physical examinations, a complete laboratory workup including serum CA 125 and imaging procedures such as PET/CT and/or CT.
Results
Of the 19 patients studied, 11 patients had recurrent cancer according to the standard of reference. Eight of these 11 patients were correctly diagnosed with CT, PET and combined PET/CT. In the remaining three patients, PET and PET/CT were positive for tumour recurrence, while CT was negative. Eight of the 19 patients were free of disease according to all three imaging modalities, and clinical follow-up produced no evidence of recurrent disease.
Twelve localisations of ovarian cancer recurrence
Discussion
CT is still the most frequently used imaging modality to monitor patients for ovarian cancer recurrence. In a study by DeRosa et al. [23], a sensitivity of no more than 47% and a specificity of 87% when assessing patients for ovarian cancer recurrence prior to a second-look operation was reported for CT. Thus, a negative CT scan does not reliably rule out ovarian cancer recurrence. In a study with eight patients, Makhija et al. [12] reported that five of them (62%), who had recurrent disease
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