The role of 18F-Fluorodeoxyglucose PET/CT in restaging patients with small cell lung cancer: a systematic review

PET/CT scan improves detection of metastatic disease compared with CT scan alone in women with high-grade neuroendocrine cervical cancer: a NeCTuR study

OBJECTIVE

To determine the optimal imaging modality for women with high-grade neuroendocrine carcinoma of the cervix.

METHODS

Women with high-grade neuroendocrine carcinoma of the cervix who had undergone a computed tomography (CT) scan and combined positron emission tomography with computed tomography (PET/CT) scan within 4 weeks of each other were identified from the NeCTuR Cervical Tumor Registry. One radiologist reviewed all CT scans, and another radiologist reviewed all PET/CT scans. The radiologists denoted the presence or absence of disease at multiple sites. Each radiologist was blinded to prior reports, patient outcomes, and the readings of the other radiologist. With findings on PET/CT used as the gold standard, sensitivity, specificity, and accuracy were calculated for CT scans.

RESULTS

Fifty matched CT and PET/CT scans were performed in 41 patients. For detecting primary disease in the cervix, CT scan had a sensitivity of 85%, a specificity of 46%, and an accuracy of 74%. For detecting disease spread to the liver, CT scan had a sensitivity of 80%, a specificity of 89%, and an accuracy of 86%. For detecting disease spread to the lung, CT had a sensitivity of 89%, a specificity of 68%, and an accuracy of 77%. Of the 14 patients who had scans for primary disease work-up, 4 (29%) had a change in their treatment plan due to the PET/CT scan. Had treatment been prescribed on the basis of the CT scan alone, 2 patients would have been undertreated, and 2 would have been overtreated.

CONCLUSION

A CT scan is inferior to a PET/CT scan in assessment of metastatic disease in women with high-grade neuroendocrine carcinoma of the cervix. Almost one-third of patients with newly diagnosed high-grade neuroendocrine cervical cancer would have received incorrect therapy had treatment planning been based solely on a CT scan. We recommend a PET/CT scan for both initial work-up and surveillance in women with high-grade neuroendocrine carcinoma of the cervix.

Bone Metastases Are Measurable: The Role of Whole-Body MRI and Positron Emission Tomography

Metastatic tumor deposits in bone marrow elicit differential bone responses that vary with the type of malignancy. This results in either sclerotic, lytic, or mixed bone lesions, which can change in morphology due to treatment effects and/or secondary bone remodeling. Hence, morphological imaging is regarded unsuitable for response assessment of bone metastases and in the current Response Evaluation Criteria In Solid Tumors 1.1 (RECIST1.1) guideline bone metastases are deemed unmeasurable. Nevertheless, the advent of functional and molecular imaging modalities such as whole-body magnetic resonance imaging (WB-MRI) and positron emission tomography (PET) has improved the ability for follow-up of bone metastases, regardless of their morphology. Both these modalities not only have improved sensitivity for visual detection of bone lesions, but also allow for objective measurements of bone lesion characteristics. WB-MRI provides a global assessment of skeletal metastases and for a one-step "all-organ" approach of metastatic disease. Novel MRI techniques include diffusion-weighted imaging (DWI) targeting highly cellular lesions, dynamic contrast-enhanced MRI (DCE-MRI) for quantitative assessment of bone lesion vascularization, and multiparametric MRI (mpMRI) combining anatomical and functional sequences. Recommendations for a homogenization of MRI image acquisitions and generalizable response criteria have been developed. For PET, many metabolic and molecular radiotracers are available, some targeting tumor characteristics not confined to cancer type (e.g. 18F-FDG) while other targeted radiotracers target specific molecular characteristics, such as prostate specific membrane antigen (PSMA) ligands for prostate cancer. Supporting data on quantitative PET analysis regarding repeatability, reproducibility, and harmonization of PET/CT system performance is available. Bone metastases detected on PET and MRI can be quantitatively assessed using validated methodologies, both on a whole-body and individual lesion basis. Both have the advantage of covering not only bone lesions but visceral and nodal lesions as well. Hybrid imaging, combining PET with MRI, may provide complementary parameters on the morphologic, functional, metabolic and molecular level of bone metastases in one examination. For clinical implementation of measuring bone metastases in response assessment using WB-MRI and PET, current RECIST1.1 guidelines need to be adapted. This review summarizes available data and insights into imaging of bone metastases using MRI and PET.