Evaluation of integrated whole-body PET/CT in the detection of recurrent ovarian cancer

https://doi.org/10.1016/j.ejrad.2005.04.006Get rights and content

Abstract

Purpose:

To assess the usefulness and reliability of integrated whole-body positron emission tomography/computed tomography (PET/CT) in patients in whom recurrent ovarian cancer is suspected.

Methods:

Integrated whole-body PET/CT imaging was performed in 19 patients with suspected ovarian cancer recurrence. CT, PET and fused PET/CT images were evaluated separately and imaging results were compared with pathological findings and clinical follow-up after 6 months.

Results:

Of the 19 patients studied, 11 were found to have recurrent cancer. In 8 of these 11 patients, recurrence was diagnosed by CT, PET and fused PET/CT. In the remaining three patients, only PET and PET/CT showed a recurrent tumour, while CT was negative. Twelve localisations of ovarian cancer recurrence could be detected by CT, 17 by PET and 18 by PET/CT. In one patient with pulmonary metastases in CT and in the CT component of PET/CT, PET was negative. In the case of three metastases in the diaphragm, the spleen and the thoracic wall, respectively, the determination of the exact localisation was only possible by fused PET/CT.

Conclusion:

In patients with recurrent ovarian cancer, PET/CT detects more lesions than PET or CT alone. PET/CT permits the exact anatomical localisation of pathologic tracer uptake and can thus direct further treatment to the precise site of tumour recurrence. Hence, PET/CT should be considered for follow-up of patients with 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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