Additional value of MR/PET fusion compared with PET/CT in the detection of lymph node metastases in cervical cancer patients
Introduction
Cervical cancer is the second most frequently diagnosed malignancy in women worldwide, and is the only major gynaecological malignancy clinically staged according to the International Federation of Obstetrics and Gynaecology (FIGO) recommendations.1 In patients with cervical cancer, the presence of lymph node metastases is associated with a poor prognosis.2, 3, 4 Lymph node involvement is also an important factor for the choice of adjuvant radiotherapy.5 Subsequent surgical staging shows that clinical staging of cervical cancers is accurate in only approximately 60% of cases,6, 7 with undiagnosed lymph node metastases being a major problem.6, 7, 8 Although nodal resection before radiotherapy results in improved survival in patients with grossly enlarged pelvic and para-aortic lymph nodes,9, 10 routine pretreatment surgical staging is not recommended because it is specialised and increases the time and cost of procedure, with an increased risk of immediate and delayed complications in patients.11, 12, 13
Recently, positron emission tomography (PET) employing the glucose analogue [18F]-flouro-2-deoxy-D-glucose (FDG) has been shown to be more sensitive than computed tomography (CT) or magnetic resonance imaging (MRI) for detecting lymph node metastases in cervical carcinoma patients.14, 15, 16, 17, 18, 19 However, PET has lower spatial resolution than CT or MRI. Fused PET/CT, as described by Beyer et al., combines the anatomic detail provided by CT with PET metabolic information.20 Initial studies have shown that this technique has improved the anatomical localisation of PET abnormalities and reduced the number of equivocal PET interpretations;21, 22, 23, 24 PET/CT has gradually become a popular modality for detecting metastatic lymph nodes in patients with cervical cancer. However, it has not yet been established whether PET/CT alone is the best imaging technique for examining patients with cervical cancer. Although it is difficult for radiologists to characterise small lymph nodes, we thought that it might improve patient management if small metastatic lymph nodes could be identified by fused MR/PET imaging preoperatively, because MRI is better for tissue characterisation when compared with CT (especially non-contrast CT). However, to date there has been no study on the additional usefulness of fused MR/PET imaging in detecting metastatic lymph nodes in patients with uterine cervical cancer.
Therefore, we performed this study to evaluate the diagnostic value of fused MR/PET imaging in the detection of metastatic lymph nodes in cervical cancer patients.
Section snippets
Patients
This was a retrospective study and our institutional review board did not require approval or informed consent for review of patients’ records or images. The inclusion criteria for patients were as follows: untreated patients with histopathologically confirmed FIGO stage IB to IVA invasive cervical cancer determined by a conventional work-up that included MR images between October 2001 and December 2007; age 29–73 years (mean = 50 years); no contraindication to the surgical procedure; no evidence
Results
There were metastatic lymph nodes in 59 (10.7%) of 553 nodal groups in 30 (38.0%) of the 79 patients. 17 patients had one metastatic nodal group, seven had two groups and six had three to five groups.
26 (44.1%) metastatic nodal groups in 26 patients were identified on PET/CT images. After review of fused MR/PET images obtained in 79 patients, the nuclear physician and radiologist changed the visual grade level score of 30 nodal groups in 28 patients which led readers to identify six more
Discussion
The presence of metastatic lymph nodes radically influences the prognosis and treatment of patients with cervical cancer.8, 9, 10, 11 In locally advanced cervical cancer patients, the 5-year survival rate in node-negative patients is 57%, and this is reduced to 34% when pelvic nodes are involved, and to 12% when para-aortic nodes are involved in surgically staged, locally advanced cervical cancer patients.28 However, the presence of lymph node metastases does not alter the clinical FIGO staging
Conflict of interest statement
None declared.
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2020, Clinical ImagingCitation Excerpt :The patient-based data included primary tumor, local recurrence, peritoneal dissemination and involvement of lymph nodes, myometrium (>50% invasion), uterine serosa, cervical serosa, adnexa, vagina, parametria, pelvic sidewall, bladder and bone [4,6,8,9,11,13,14]. The lesion-based data included lymph nodes, primary tumor, local recurrence, lesions involving the peritoneum, liver, lung, bone, pleura and abdominal metastases [4,5,11–14]. To reduce clinical (pretest probability of malignancy) and methodological heterogeneity, our primary diagnostic performance analysis for PET/MRI and PET/CT included only studies in which both modalities were performed in the same cohort.