Claire Tabouret-Viaud

PET/MR in Breast Cancer

Breast cancer is an international public health concern in which an optimal treatment plan requires a precise staging. Both MRI and PET imaging techniques have made significant progress in the last decades with constant improvements that made both modalities clinically relevant in several stages of breast cancer management and follow-up. On one hand, specific breast MRI permits high diagnostic accuracy for local tumor staging, and whole-body MRI can also be of great use in distant staging, eventually accompanied by organ-specific MRI sequences. Moreover, many different MRI sequences can be performed, including functional MRI, letting us foresee important improvements in breast cancer characterization in the future. On the contrary, (18)F-FDG-PET has a high diagnostic performance for the detection of distant metastases, and several other tracers currently under development may profoundly affect breast cancer management in the future with better determination of different types of breast cancers allowing personalized treatments. As a consequence PET/MR is a promising emerging technology, and it is foreseeable that in cases where both PET and MRI data are needed, a hybrid acquisition is justified when available. However, at this stage of deployment of such hybrid scanners in a clinical setting, more data are needed to demonstrate their added value beyond just patient comfort of having to undergo a single examination instead of two, and the higher confidence of diagnostic interpretation of these co-registered images. Optimized imaging protocols are still being developed and are prone to provide more efficient hybrid protocols with a potential improvement in diagnostic accuracy. More convincing studies with larger number of patients as well as cost-effectiveness studies are needed. This article provides insights into the current state-of-the-art of PET/MR in patients with breast cancer and gives an outlook on future developments of both imaging techniques and potential applications in the future.

Target Definition in Salvage Radiotherapy for Recurrent Prostate Cancer: The Role of Advanced Molecular Imaging

Salvage radiotherapy (SRT) represents the main treatment option for relapsing prostate cancer in patients after radical prostatectomy. Several open questions remain unanswered in terms of target volumes definition and delivered doses for SRT: the effective dose necessary to achieve biochemical control in the SRT setting may be different if the tumor recurrence is micro- or macroscopic. At the same time, irradiation of only the prostatic bed or of the whole pelvis will depend on the localization of the recurrence, local or locoregional. In the “theragnostic imaging” era, molecular imaging using positron emission tomography (PET) constitutes a useful tool for clinicians to define the site of the recurrence, the extent of disease, and individualize salvage treatments. The best option currently available in clinical routine is the combination of radiolabeled choline PET imaging and multiparametric magnetic resonance imaging (MRI), associating the nodal and distant metastases identification based on PET with the local assessment by MRI. A new generation of targeted tracers, namely, prostate-specific membrane antigen, show promising results, with a contrast superior to choline imaging and a higher detection rate even for low prostate-specific antigen levels; validation studies are ongoing. Finally, imaging targeting bone remodeling, using whole-body SPECT–CT, is a relevant complement to molecular/metabolic PET imaging when bone involvement is suspected.

Long-term Results of a Comparative PET/CT and PET/MRI Study of 11 C-Acetate and 18 F-Fluorocholine for Restaging of Early Recurrent Prostate Cancer

Purpose The aims of this study were to assess the intraindividual performance of 18F-fluorocholine (FCH) and 11C-acetate (ACE) PET studies for restaging of recurrent prostate cancer (PCa), to correlate PET findings with long-term clinical and imaging follow-up, and to evaluate the impact of PET results on patient management. Methods Thirty-three PCa patients relapsing after radical prostatectomy (n = 10, prostate-specific antigen [PSA] ⩽3 ng/mL), primary radiotherapy (n = 8, prostate-specific antigen ⩽5 ng/mL), or radical prostatectomy + salvage radiotherapy (n = 15) underwent ACE and FCH PET-CT (n = 29) or PET-MRI (n = 4) studies in a randomized sequence 0 to 21 days apart. Results The detection rate for ACE was 66% and for FCH was 60%. Results were concordant in 79% of the cases (26/33) and discordant in 21% (retroperitoneal, n = 5; pararectal, n = 1; and external iliac nodes, n = 1). After a median FU of 41 months (n = 32, 1 patient lost to FU), the site of relapse was correctly identified by ACE and FCH in 53% (17/32) and 47% (15/32) of the patients, respectively (2 M1a patients ACE+/FCH−), whereas in 6 of 32 patients the relapse was not localized. Treatment approach was changed in 11 (34.4%) of 32 patients and 9 (28%) of 32 patients restaged with ACE and FCH PET, respectively. Conclusions In early recurrent PCa, ACE and FCH showed minor discrepancies, limited to nodal staging and mainly in the retroperitoneal area, with true positivity of PET findings confirmed in half of the cases during FU. Treatment approach turned out to be influenced by ACE or FCH PET studies in one third of the patients.

High protracted 99mTc-HDP uptake in synthetic bone implants — A potentially misleading incidental finding on bone scintigraphy

We report the case of a 56-year-old male with bilateral total knee prostheses suffering from bilateral knee pain mainly on the right side and referred for bone scintigraphy. The medical history of the patient revealed an opening wedge high tibial osteotomy performed nine years earlier, with insertion of two blocks of ceramic made of hydroxyapatite and tricalcium phosphate in a wedge configuration as synthetic bone substitutes. The porous structure of these implants is analogous to the architecture of cancellous bone and permits fibrovascular and bone ingrowth, promoting the healing process. Planar scintigraphy and SPECT/CT showed an intense uptake within those implants in the early phase as well as in the late phase of the bone scan. It also showed bilateral patellofemoral arthritis. A (99m)Tc-labeled antigranulocyte antibody scintigraphy was negative for infection or inflammation. Bilateral patellar resurfacing led to complete symptom regression, confirmed at 10 months follow-up. To the best of our knowledge, this scintigraphic pattern with such a high tracer uptake reflecting bone substitute osteointegration has not yet been published. This should be considered in patients with such bone replacement materials that are increasingly used, in order to avoid false diagnosis of inflammation or infection.

Isolated tumor cells in sentinel lymph nodes of invasive breast cancer: cell displacement or metastasis?

The goal of this study was to determine whether the presence of isolated tumoral cells (ITCs) in sentinel lymph nodes (SLNs) after core needle biopsy (CNB) is related to the time interval between CNB and surgery and to histopathologic features of invasive breast cancer. Data from 633 consecutive patients with no micrometastasis or metastasis on both frozen sections and definitive pathologic examination of SLNs were retrieved from a prospective data base. No association was found between ITCs and the time interval between CNB and SLNB. The association was significant with tumor size, the tumor lymphovascular invasion (LVI) and the histologic type of the tumor. This study adds supplementary data to the association between tumoral LVI and ITCs in SLNs, The time interval between CNB procedure and SLNB was not related to affect presence of ITCs, which might not suggest the iatrogenic origin of these cells.

Whole-Body SPECT/CT versus Planar Bone Scan with Targeted SPECT/CT for Metastatic Workup

Purpose The use of SPECT/CT in bone scans has been widespread in recent years, but there are no specific guidelines concerning the optimal acquisition protocol. Two strategies have been proposed: targeted SPECT/CT for equivocal lesions detected on planar images or systematic whole-body SPECT/CT. Our aim was to compare the diagnostic accuracy of the two approaches. Methods 212 consecutive patients with a history of cancer were referred for bone scans to detect bone metastases. Two experienced readers randomly evaluated for each patient either planar images with one-field SPECT/CT targeted on equivocal focal uptakes (targeted SPECT/CT) or a whole-body (two-field) SPECT/CT acquisition from the base of the skull to the proximal femurs (whole-body SPECT/CT). The exams were categorized as “nonmetastatic,” “equivocal,” or “metastatic” on both protocols. The presence or absence of any extra-axial skeletal lesions was also assessed. The sensitivity and specificity of both strategies were measured using the results of subsequent imaging follow-up as the reference standard. Results Whole-body SPECT/CT had a significantly higher sensitivity than targeted SPECT/CT to detect bone metastases (p = 0.0297) and to detect extra-axial metastases (p = 0.0266). There was no significant difference in specificity among the two approaches. Conclusion Whole-body SPECT/CT is the optimal modality of choice for metastatic workup, including detection of extra-axial lesions, with improved sensitivity and similar specificity compared to targeted SPECT/CT.

Severe early basal ganglia hypometabolism in neurodegeneration with brain iron accumulation.

Neurodegeneration with brain iron accumulation (NBIA) is a group of rare genetic neurological disorders characterized by iron deposits in the basal ganglia. Apart from the iron accumulation identified on MRI, the role of imaging modalities is limited [1]. Here we present the metabolic findings in a 45-year-old man with NBIA. After a 14year history of psychiatric symptoms, the patient was referred to our institution for cognitive decline and parkinsonian symptoms, which had developed progressively during the previous 4 years. Brain MRI showed global atrophy and iron accumulation in the caudate and dentate nuclei, putamen, globus pallidus and substantia nigra, bilaterally, as signal hypointensities on the gradient echo T2 sequence (a). Further investigation by F-FDG PET revealed severe metabolic reduction exclusively in the basal ganglia, as shown on the PET/ MRI image (b), the PET image (c) and the BRASS software deviation image (d), that was retrospectively found to be already decreased on a previous PET scan performed 12 years earlier when the MRI scan was still normal. Cortical, thalamic and cerebellar metabolism was within the normal range, contrary to previous reports in NBIA [2, 3]. This metabolic pattern is typically associated with Huntington’s disease (HD), in which the caudate and putamen are already affected in the preclinical phase of the disease, with gradual cortical involvement [4]. Early iron accumulation in the basal ganglia has been found in HD as well, but the typical finding is marked atrophy of the caudate nuclei with ex-vacuo dilatation of * Ismini C. Mainta isminicharis.mainta@hcuge.ch

PET/MRI in Breast Cancer

Breast cancer is the most common cancer in women worldwide, and represented more than 25% of the newly diagnosed cancer cases in women in 2016. PET/CT is recommended in the clinical workup of advanced breast cancers and in cases of breast cancer recurrence and may also be proposed in treatment monitoring. PET/MRI is a new imaging technique which is now being used clinically in different countries, and which may replace PET/CT in some selected breast cancer patients, when available. A detailed description of advantages and indications of, respectively, PET and MRI techniques taken separately in breast cancer patients is beyond the scope of the present work and has already been reviewed elsewhere by our group. We focused on the technical advantages and disadvantages of combined PET/MRI acquisitions in breast cancer patients from diagnosis to follow-up. In this chapter, we cover the specifics of PET/MRI in terms of quantification and provide a summary of the different protocols performed in breast cancer PET/MRI imaging. We will also discuss the clinical advances for patient management, the potential improvements that may occur in the future, as well as the future role that may be given to this technique.