PET/MR Outperforms PET/CT in Suspected Occult Tumors

Application of 18F-FDG Positron Emission Tomography/Magnetic Resonance in Evaluation of Oropharyngeal Carcinoma

Objectives: Oropharyngeal carcinoma is experiencing an increase in incidence and can easily metastasize to the cervical lymph nodes. Therefore, evaluating the tumor boundary and lymph node metastasis before treatment is critical. Both CT and MR may have limitations in describing the specific boundaries of oropharyngeal tumors. To date, no research has applied PET/MR imaging to patients with only oropharyngeal carcinoma and verified its diagnostic value. The aim of our study was to evaluate the diagnostic value of PET/MR in patients with oropharyngeal carcinoma. We prepared PET/MR for comparison with CT/MR for T and N staging, with the aim of exploring the relationship between the imaging parameters and different biological factors. Methods: This was a retrospective, observational study. In total, 13 patients (11 males and 2 females) with oropharyngeal tumors who underwent FDG PET/MR and enhanced CT/MR from July 2021 to December 2022 were retrospectively analyzed. Cohen's kappa coefficient and the McNemar test were used to compare the consistencies and diagnostic values of FDG PET/MR and enhanced CT/MR imaging in relation to primary tumors and cervical lymph node metastases. Various specific parameters of FDG PET/MR were included in the statistics. Spearman correlation coefficients were used to analyze the relationship between the parameters and the tumor stage, the degree of differentiation, p16 expression, Ki67 expression, and serological tumor markers. Results: The average age of the patients was 61.54 ± 6.62 years old. Preoperative imaging demonstrated good consistency between FDG PET/MR and enhanced CT and MR for the diagnosis of clinical T stage. A total of seven patients underwent surgery directly. Overall, 231 cervical lymph nodes were dissected. Compared to the postoperative histopathological results, PET/MR was significantly more sensitive than enhanced CT/MR imaging (78.57% vs. 50.00%, p < 0.05; 78.57% vs. 64.29%, p < 0.05, respectively). Also, PET/MR showed more accuracy in diagnosing metastatic lymph nodes, but without significance. Combined with PET/MR-specific parameters, the SUV, TLG, and the MTV were found to be higher in the patients with more advanced stages of cancer and lower in those with p16-positive tumors. In addition, they were found to be positively correlated with the level of serum CEA. Conclusions: This is the first study to evaluate the clinical diagnostic value of PET/MR in patients with oropharyngeal carcinoma. We believe that PET/MR has more advantages in describing tumor boundaries. It is more sensitive or even more accurate for the evaluation of metastatic cervical lymph nodes.

Orthopedic surgical treatment of osteomalacia induced by culprit soft tissue tumor in the hip region: a single-center retrospective study

BACKGROUND

Due to its occult position, complex anatomical structure, and spatial relationships, the causative tumor of Tumor-Induced Osteomalacia (TIO) in the hip region is quite difficult to detect and qualitatively diagnose in clinical practice. In this regard, clinicians often lack sufficient knowledge about such tumors, leading to frequent missed diagnoses, misdiagnoses, and unreasonable treatment.

OBJECTIVE

This study aimed to investigate the clinical characteristics of TIO patients with culprit soft tissue tumors in the hip region and evaluate the effect of surgical treatment on these individuals to improve clinicians' understanding of the rare phenomenon.

METHODS

The clinical data of all patients, from January 2013 to January 2023, who underwent surgical treatment for hip located culprit soft tissue tumors by the subspecialty group on bone and soft tissue tumors at our institution, were retrospectively analysed. Specifically, the clinical characteristics and therapeutic effects were examined and the patients' clinical experience was summarized.

RESULTS

Twenty-two patients, who met the inclusion criteria, were included. All patients experienced varying degrees of bone pain, commonly accompanied by weakness (16/22) and limited mobility (21/22), and 10 patients (45.5%) experienced a significant reduction in body height during the course of the disease. All patients underwent orthopedic surgery in the hip region, as hypophosphatemia occurred in all of them. Pathological diagnosis was confirmed to be consistent with causative tumors of TIO. All patients experienced a gradual increase in serum phosphorus postoperatively during short-term follow-up. The follow-up period was between 1 and 10 years, and the postoperative serum phosphorus levels were monitored at our hospital or other facilities close to the patients.

CONCLUSIONS

Oncogenic soft tissue tumors for TIO in the hip region are occult, making clinical misdiagnoses or missed diagnoses highly likely. Therefore, enhancing the clinician's understanding of this rare condition is imperative. Notably, for TIO patient whose culprit tumor can be located, complete surgical resection of the causative tumor is the best treatment option. Furthermore, close postoperative monitoring of serum phosphorus is necessary, and patients should be subjected to long-term follow-up for prompt detection of recurrent conditions.

Recurrence Detection by Hybrid [ 18F]FDG-PET in Advanced Head and Neck Squamous Cell Carcinoma

BACKGROUND

In the clinical management of advanced stage head and neck squamous cell carcinoma, the use of hybrid [18F]FDG-PET imaging is well established. However, there is ongoing debate regarding the optimal frequency of hybrid PET scans to be included in follow-up protocols, particularly if the initial post-therapeutic scan is negative.

METHODS

We conducted a single-center 10-year retrospective study involving all patients who underwent hybrid PET scans for the follow-up of advanced stage head and neck cancer. A total of 285 patients were included.

RESULTS

Out of 199 patients with a negative 3-month hybrid PET, 15% subsequently developed a recurrence during further follow-up. Notably, 90% of these recurrences were detected by hybrid PET.

CONCLUSION

Fifteen percent of patients with a negative 3-month hybrid PET experienced a recurrence. Given that the majority of recurrences were detected by hybrid PET scans, there is a compelling argument for incorporating regular repetitive scans during follow-up.

Role of 18F-FDG PET/CT in Head and Neck Squamous Cell Carcinoma: Current Evidence and Innovative Applications

This article provides an overview of the use of 18F-FDG PET/CT in various clinical scenarios of head-neck squamous cell carcinoma, ranging from initial staging to treatment-response assessment, and post-therapy follow-up, with a focus on the current evidence, debated issues, and innovative applications. Methodological aspects and the most frequent pitfalls in head-neck imaging interpretation are described. In the initial work-up, 18F-FDG PET/CT is recommended in patients with metastatic cervical lymphadenectomy and occult primary tumor; moreover, it is a well-established imaging tool for detecting cervical nodal involvement, distant metastases, and synchronous primary tumors. Various 18F-FDG pre-treatment parameters show prognostic value in terms of disease progression and overall survival. In this scenario, an emerging role is played by radiomics and machine learning. For radiation-treatment planning, 18F-FDG PET/CT provides an accurate delineation of target volumes and treatment adaptation. Due to its high negative predictive value, 18F-FDG PET/CT, performed at least 12 weeks after the completion of chemoradiotherapy, can prevent unnecessary neck dissections. In addition to radiomics and machine learning, emerging applications include PET/MRI, which combines the high soft-tissue contrast of MRI with the metabolic information of PET, and the use of PET radiopharmaceuticals other than 18F-FDG, which can answer specific clinical needs.

Advances in determining the gross tumor target volume for radiotherapy of brain metastases

Brain metastases (BMs) are the most prevalent intracranial malignant tumors in adults and are the leading cause of mortality attributed to malignant brain diseases. Radiotherapy (RT) plays a critical role in the treatment of BMs, with local RT techniques such as stereotactic radiosurgery (SRS)/stereotactic body radiotherapy (SBRT) showing remarkable therapeutic effectiveness. The precise determination of gross tumor target volume (GTV) is crucial for ensuring the effectiveness of SRS/SBRT. Multimodal imaging techniques such as CT, MRI, and PET are extensively used for the diagnosis of BMs and GTV determination. With the development of functional imaging and artificial intelligence (AI) technology, there are more innovative ways to determine GTV for BMs, which significantly improve the accuracy and efficiency of the determination. This article provides an overview of the progress in GTV determination for RT in BMs.

Preoperative evaluation and orthopedic surgical strategies for tumor-induced osteomalacia

Tumor-induced osteomalacia (TIO), also known as oncogenic osteomalacia, is very rare, with about 1000 reported cases globally. Removing most TIO culprit tumors requires the evaluation and intervention of orthopedic doctors. However, orthopedic doctors often have a poor understanding of the optical treatment of TIO due to its rarity. In addition, most TIO patients lack specific clinical manifestations. Also, the clinical localization and qualitative diagnosis of TIO are difficult and thus can easily be misdiagnosed and mistreated. Furthermore, the true incidence rate of TIO may be underestimated. Although many breakthroughs have been made in exploring the pathogenesis, clinical diagnosis, and treatment of TIO, rational and standardized orthopedic surgical treatment experience summary and sorting for TIO patients are lacking. In this article, the recent experience and progress in the field of orthopedic surgical treatment for TIO globally have been summarized, providing a theoretical basis and new clinical practice guidance for the rational treatment of TIO patients.

Diagnostic performance of whole-body [18F]FDG PET/MR in cancer M staging: A systematic review and meta-analysis

OBJECTIVES

To calculate the pooled diagnostic performances of whole-body [18F]FDG PET/MR in M staging of [18F]FDG-avid cancer entities.

METHODS

A diagnostic meta-analysis was conducted on the [18F]FDG PET/MR in M staging, including studies: (1) evaluated [18F]FDG PET/MR in detecting distant metastasis; (2) compared[ 18F]FDG PET/MR with histopathology, follow-up, or asynchronous multimodality imaging as the reference standard; (3) provided data for the whole-body evaluation; (4) provided adequate data to calculate the meta-analytic performances. Pooled performances were calculated with their confidence interval. In addition, forest plots, SROC curves, and likelihood ratio scatterplots were drawn. All analyses were performed using STATA 16.

RESULTS

From 52 eligible studies, 2289 patients and 2072 metastases were entered in the meta-analysis. The whole-body pooled sensitivities were 0.95 (95%CI: 0.91-0.97) and 0.97 (95%CI: 0.91-0.99) at the patient and lesion levels, respectively. The pooled specificities were 0.99 (95%CI: 0.97-1.00) and 0.97 (95%CI: 0.90-0.99), respectively. Additionally, subgroup analyses were performed. The calculated pooled sensitivities for lung, gastrointestinal, breast, and gynecological cancers were 0.90, 0.93, 1.00, and 0.97, respectively. The pooled specificities were 1.00, 0.98, 0.97, and 1.00, respectively. Furthermore, the pooled sensitivities for non-small cell lung, colorectal, and cervical cancers were 0.92, 0.96, and 0.86, respectively. The pooled specificities were 1.00, 0.95, and 1.00, respectively.

CONCLUSION

[18F]FDG PET/MR was a highly accurate modality in M staging in the reported [18F]FDG-avid malignancies. The results showed high sensitivity and specificity in each reviewed malignancy type. Thus, our findings may help clinicians and patients to be confident about the performance of [18F]FDG PET/MR in the clinic.

CLINICAL RELEVANCE STATEMENT

Although [18F]FDG PET/MR is not a routine imaging technique in current guidelines, mostly due to its availability and logistic issues, our findings might add to the limited evidence regarding its performance, showing a sensitivity of 0.95 and specificity of 0.97.

KEY POINTS

• The whole-body [18F]FDG PET/MR showed high accuracy in detecting distant metastases at both patient and lesion levels. • The pooled sensitivities were 95% and 97% and pooled specificities were 99% and 97% at patient and lesion levels, respectively. • The results suggested that 18F-FDG PET/MR was a strong modality in the exclusion and confirmation of distant metastases.

Pelvic metastatic squamous cell carcinoma of unknown primary site: A case report and brief literature review

RATIONALE

Cancer with unknown primary site is a kind of disease that is difficult to deal with clinically, accounting for 2% to 9% of all newly diagnosed cancer cases. Here, we report such a case with pelvic metastatic squamous cell carcinoma of an unknown primary site and review the relevant literature.

PATIENT CONCERNS DIAGNOSES

A 43-year-old Chinese female patient was referred to our hospital and initially diagnosed as "malignant tumor of right adnexal area?, obstruction of right ureter, secondary hydronephrosis".

INTERVENTIONS

Thereafter cytoreductive surgery was performed which included a total hysterectomy, left adnexectomy, partial omentum resection, pelvic lymph node dissection, and para-aortic lymph node dissection. The primary lesion could not be identified by supplementary examination and postoperative pathology. The patient was diagnosed as pelvic metastatic squamous cell carcinoma whose primary site was unknown. To prevent a recurrence, we administered adjuvant chemotherapy for the patient.

OUTCOMES

The patient was followed up after treatment, complete remission has been maintained for 72 months, and no recurrence or metastasis has been found.

LESSONS

Our case demonstrates that surgery combined with chemotherapy could be helpful for pelvic metastatic squamous cell carcinoma of unknown primary site.

Added value of regional 18F-FDG PET/MRI-assisted whole-body 18F-FDG PET/CT in malignant ascites with unknown primary origin

BACKGROUND

Comparing to PET/CT, integrative PET/MRI imaging provides superior soft tissue resolution. This study aims to evaluate the added value of regional delayed 18F-FDG PET/MRI-assisted whole-body 18F-FDG PET/CT in diagnosing malignant ascites patients.

RESULTS

The final diagnosis included 22 patients with ovarian cancer (n = 11), peritoneal cancer (n = 3), colon cancer (n = 2), liver cancer (n = 2), pancreatic cancer (n = 2), gastric cancer (n = 1), and fallopian tube cancer (n = 1). The diagnosis of the primary tumor using whole-body PET/CT was correct in 11 cases. Regional PET/MRI-assisted whole-body PET/CT diagnosis was correct in 18 cases, including 6 more cases of ovarian cancer and 1 more case of fallopian tube cancer. Among 4 cases that were not diagnosed correctly, 1 case had the primary tumor outside of the PET/MRI scan area, 2 cases were peritoneal cancer, and 1 case was colon cancer. The diagnostic accuracy of regional PET/MRI-assisted whole-body PET/CT was higher than PET/CT alone (81.8% vs. 50.0%, κ 2 = 5.14, p = 0.023). The primary tumor conspicuity score of PET/MRI was higher than PET/CT (3.67 ± 0.66 vs. 2.76 ± 0.94, P < 0.01). In the same scan area, more metastases were detected in PET/MRI than in PET/CT (156 vs. 86 in total, and 7.43 ± 5.17 vs. 4.10 ± 1.92 per patient, t = 3.89, P < 0.01). Lesion-to-background ratio in PET/MRI was higher than that in PET/CT (10.76 ± 5.16 vs. 6.56 ± 3.45, t = 13.02, P < 0.01).

CONCLUSION

Comparing to whole-body PET/CT alone, additional delayed regional PET/MRI with high soft tissue resolution is helpful in diagnosing the location of the primary tumor and identifying more metastases in patients with malignant ascites. Yet larger sample size in multicenter and prospective clinical researches is still needed.

ACR Appropriateness Criteria® Staging and Post-Therapy Assessment of Head and Neck Cancer

Imaging of head and neck cancer at initial staging and as part of post-treatment surveillance is a key component of patient care as it guides treatment strategy and aids determination of prognosis. Head and neck cancer includes a heterogenous group of malignancies encompassing several anatomic sites and histologies, with squamous cell carcinoma the most common. Together this comprises the seventh most common cancer worldwide. At initial staging comprehensive imaging delineating the anatomic extent of the primary site, while also assessing the nodal involvement of the neck is necessary. The treatment of head and neck cancer often includes a combination of surgery, radiation, and chemotherapy. Post-treatment imaging is tailored for the evaluation of treatment response and early detection of local, locoregional, and distant recurrent tumor. Cross-sectional imaging with CT or MRI is recommended for the detailed anatomic delineation of the primary site. PET/CT provides complementary metabolic information and can map systemic involvement. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

International EANM-SNMMI-ISMRM consensus recommendation for PET/MRI in oncology

PREAMBLE

The Society of Nuclear Medicine and Molecular Imaging (SNMMI) is an international scientific and professional organization founded in 1954 to promote the science, technology, and practical application of nuclear medicine. The European Association of Nuclear Medicine (EANM) is a professional non-profit medical association that facilitates communication worldwide between individuals pursuing clinical and research excellence in nuclear medicine. The EANM was founded in 1985. The merged International Society for Magnetic Resonance in Medicine (ISMRM) is an international, nonprofit, scientific association whose purpose is to promote communication, research, development, and applications in the field of magnetic resonance in medicine and biology and other related topics and to develop and provide channels and facilities for continuing education in the field.The ISMRM was founded in 1994 through the merger of the Society of Magnetic Resonance in Medicine and the Society of Magnetic Resonance Imaging. SNMMI, ISMRM, and EANM members are physicians, technologists, and scientists specializing in the research and practice of nuclear medicine and/or magnetic resonance imaging. The SNMMI, ISMRM, and EANM will periodically define new guidelines for nuclear medicine practice to help advance the science of nuclear medicine and/or magnetic resonance imaging and to improve the quality of service to patients throughout the world. Existing practice guidelines will be reviewed for revision or renewal, as appropriate, on their fifth anniversary or sooner, if indicated. Each practice guideline, representing a policy statement by the SNMMI/EANM/ISMRM, has undergone a thorough consensus process in which it has been subjected to extensive review. The SNMMI, ISMRM, and EANM recognize that the safe and effective use of diagnostic nuclear medicine imaging and magnetic resonance imaging requires specific training, skills, and techniques, as described in each document. Reproduction or modification of the published practice guideline by those entities not providing these services is not authorized. These guidelines are an educational tool designed to assist practitioners in providing appropriate care for patients. They are not inflexible rules or requirements of practice and are not intended, nor should they be used, to establish a legal standard of care. For these reasons and those set forth below, the SNMMI, the ISMRM, and the EANM caution against the use of these guidelines in litigation in which the clinical decisions of a practitioner are called into question. The ultimate judgment regarding the propriety of any specific procedure or course of action must be made by the physician or medical physicist in light of all the circumstances presented. Thus, there is no implication that an approach differing from the guidelines, standing alone, is below the standard of care. To the contrary, a conscientious practitioner may responsibly adopt a course of action different from that set forth in the guidelines when, in the reasonable judgment of the practitioner, such course of action is indicated by the condition of the patient, limitations of available resources, or advances in knowledge or technology subsequent to publication of the guidelines. The practice of medicine includes both the art and the science of the prevention, diagnosis, alleviation, and treatment of disease. The variety and complexity of human conditions make it impossible to always reach the most appropriate diagnosis or to predict with certainty a particular response to treatment. Therefore, it should be recognized that adherence to these guidelines will not ensure an accurate diagnosis or a successful outcome. All that should be expected is that the practitioner will follow a reasonable course of action based on current knowledge, available resources, and the needs of the patient to deliver effective and safe medical care. The sole purpose of these guidelines is to assist practitioners in achieving this objective.

18F-FDG PET/MRI in Detection of Pulmonary Malignancies: A Systematic Review and Meta-Analysis

Background There have been conflicting results regarding fluorine 18-labeled fluorodeoxyglucose (¹⁸F-FDG) PET/MRI diagnostic performance in lung malignant neoplasms. Purpose To evaluate the diagnostic performance of ¹⁸F-FDG PET/MRI for the detection of pulmonary malignant neoplasms. Materials and Methods A systematic search was conducted within the Scopus, Web of Science, and PubMed databases until December 31, 2021. Published original articles that met the following criteria were considered eligible for meta-analysis: (a) detecting malignant lesions in the lung, (b) comparing ¹⁸F-FDG PET/MRI with a valid reference standard, and (c) providing data for the meta-analytic calculations. A hierarchical method was used to pool the performances. The bivariate model was used to find the summary points and 95% CIs. The hierarchical summary receiver operating characteristic model was used to draw the summary receiver operating characteristic curve and calculate the area under the curve. The Higgins I² statistic and Cochran Q test were used for heterogeneity assessment. Results A total of 43 studies involving 1278 patients met the inclusion criteria and were included in the meta-analysis. ¹⁸F-FDG PET/MRI had a pooled sensitivity and specificity of 96% (95% CI: 84, 99) and 100% (95% CI: 98, 100), respectively. ¹⁸F-FDG PET/CT had a pooled sensitivity and specificity of 99% (95% CI: 61, 100) and 99% (95% CI: 94, 100), respectively, which were comparable with those of ¹⁸F-FDG PET/MRI. At meta-regression, studies in which contrast media (P = .03) and diffusion-weighted imaging (P = .04) were used as a part of a pulmonary ¹⁸F-FDG PET/MRI protocol showed significantly higher sensitivities. Conclusion Fluorine 18-labeled fluorodeoxyglucose (¹⁸F-FDG) PET/MRI was found to be accurate and comparable with ¹⁸F-FDG PET/CT in the detection of malignant pulmonary lesions, with significantly improved sensitivity when advanced acquisition protocols were used. © RSNA, 2023 Supplemental material is available for this article.

Comparison of whole-body 18F-FDG PET/CT and PET/MRI for distant metastases in patients with malignant tumors: a meta-analysis

BACKGROUND

As a first-line imaging modality, whole-body fluorine-18 fluorodeoxyglucose (18F-FDG) positron emission tomography (PET)/computed tomography (CT) and 18F-FDG PET/magnetic resonance imaging (MRI) had been widely applied in clinical practice. However, 18F-FDG PET/MRI may be superior to PET/CT for the diagnosis of distant metastases in patients with advanced-stage. Therefore, it is timely and important to systematically determine the diagnostic accuracy of 18F-FDG PET/MRI compared with that of 18F-FDG PET/CT for the diagnosis of distant metastases.

METHODS

This study aimed to compare the diagnostic accuracy of 18F-FDG PET/CT and PET/MRI for the diagnosis of distant metastases in patients with malignant tumors. Relevant studies using both 18F-FDG PET/CT and PET/MRI for assessment of distant metastases in patients with malignant tumors were searched in PubMed, Embase, The Cochrane Library, and Scopus from January 2010 to November 2023. Two reviewers independently selected studies according to the inclusion and exclusion criteria. A reviewer extracted relevant data and assessed the quality of the eligible studies. The pooled sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, and area under the summary receiver operating characteristic curve (AUC) for 18F-FDG PET/CT and PET/MRI were analyzed. Subgroup analysis was performed.

RESULTS

Across 14 studies (1042 patients), 18F-FDG PET/MRI had a higher sensitivity (0.87 versus 0.81), AUC value (0.98 versus 0.95), and similar specificity (0.97 versus 0.97), than PET/CT for detecting distant metastases. In 3 studies of breast cancer (182 patients), 18F-FDG PET/MRI had a higher sensitivity (0.95 versus 0.87) and specificity (0.96 versus 0.94) than PET/CT. In 5 studies of lung cancer (429 patients), 18F-FDG PET/CT had a higher sensitivity (0.87 versus 0.84) and a lower specificity (0.95 versus 0.96) to PET/MRI.

CONCLUSIONS

18F-FDG PET/MRI and PET/CT both performed well as detectors of distant metastases in patients with malignant tumors, and the former has higher sensitivity. The subgroup analysis highlights that 18F-FDG PET/MRI and PET/CT hold different advantages for distant metastases staging in different tumors, PET/MRI has a higher accuracy in patients with breast cancer patients, while PET/CT has a higher accuracy in patients with lung cancer.

FDG-PET-CT/MRI in head and neck squamous cell carcinoma: Impact on pretherapeutic N classification, detection of distant metastases, and second primary tumors

BACKGROUND

To assess the effect of 18-fluorodeoxyglucose positron emission tomography (FDG-PET) in the pretherapeutic staging of N classification, detection rate of distant metastases, and second primaries.

METHODS

Retrospective study on patients with head and neck carcinoma. We compared pretherapeutic N classification by ultrasound, computed tomography (CT)/magnetic resonance imaging (MRI), and FDG-PET-CT/MRI.

RESULTS

A change in the N classification due to FDG-PET-CT/MRI was observed in 116 patients (39.5%) compared to N classification by ultrasound and fine-needle aspiration cytology. Patients with advanced nodal classification (>N2a) were more likely to be reclassified. Distant metastases were detected in 19 patients and a total of 36 second primaries were diagnosed by FDG-PET-CT/MRI. Detection of distant metastases was more likely in regional advanced disease (>N2a). Smokers (>10 py) had a significantly higher risk of second primary.

CONCLUSION

FDG-PET-CT/MRI leads to a significant change in pretherapeutic N classification. The cumulative incidence of distant metastases and second primaries was 18.7%.

[Cervical CUP syndrome]

The term CUP syndrome (cancer of unknown primary) refers to a multifaceted clinical picture in which the affected patients have lymph node and/or distant metastases without the location of the primary tumor being known. The criteria of CUP syndrome are fulfilled if a histologically or cytologically confirmed malignancy is present without a detectable primary tumor after completion of the primary diagnosis. Due to the usually poor prognosis and the manifold appearance, which often does not allow a standardized therapy, cervical CUP syndrome makes specific demands on clinical and imaging diagnostics. Using modern techniques such as positron emission tomography-computed tomography (PET-CT), imaging plays a key role in the detection of a possible occult primary tumor as well as in staging and prognosis assessment.

Predictive value of suvmax changes between two sequential post-therapeutic FDG-pet in head and neck squamous cell carcinomas

18-flurodesoxyglucose position emission tomography (FDG-PET) with computed tomography (CT) or magnetic resonance imaging (MRI) is a broadly accepted tool for pretherapeutic staging and post-therapeutic assessment of response. The prognostic value of sequential post-therapeutic FDG-PETs and the impact of change in metabolic activity has been scarcely reported so far. We hypothesized that an increase in metabolic activity (as measured by maximum standardized uptake value, SUVmax) would be predictive for recurrence. We retrospectively assessed all oral, oropharyngeal, laryngeal, and hypopharyngeal squamous cell carcinoma patients treated at the Department of Otorhinolaryngology-Head and Neck Surgery, University Hospital Zurich between April 1st, 2010 and September 30th, 2018 (N = 337). After a negative post-treatment FDG-PET at 3 months, we measured the SUVmax of the local tumor area and the regional lymph nodes on follow-up FDG-PET at 9 months. We then correlated SUVmax difference between 9 and 3 months with tumor recurrence using Kaplan Meier analysis. During follow-up, 68 patients (20.2%) had local recurrence and 53 had regional recurrence (15.7%) at a median time of 9.0 (IQR 4.25-14) and 7.0 (IQR 5.25-23) months, respectively. An increase in local and/or regional SUVmax from the 3 months to the 9 months post-therapeutic FDG-PET resulted in a poorer recurrence-free survival (Log rank, P = 0.001, for both). An increase in local SUVmax between 3 and 9 months was associated with a hazard ratio of 4.17 for recurrence (95%CI 1.89-9.2, P = 0.0003). In conclusion, an increase in metabolic activity/SUVmax between two post-therapeutic FDG-PETs requires a histological examination as it is associated with tumor recurrence.

PET/MR in Head and Neck Cancer - An Update

In academic centers, PET/MR has taken the road to clinical nuclear medicine in the past 6 years since the last review on its applications in head and neck cancer patients in this journal. Meanwhile, older sequential PET + MR machines have largely vanished from clinical sites, being replaced by integrated simultaneous PET/MR scanners. Evidence from several studies suggests that PET/MR overall performs equally well as PET/CT in the staging and restaging of head and neck cancer and in radiation therapy planning. PET/MR appears to offer advantages in the characterization and prognostication of head and neck malignancies through multiparametric imaging, which demands an exact preparation and validation of imaging modalities, however. The majority of available clinical PET/MR studies today covers FDG imaging of squamous cell carcinoma arising from a broad spectrum of locations in the upper aerodigestive tract. In the future, specific PET/MR studies are desired that address specific histopathological tumor entities, nonepithelial malignancies, such as major salivary gland tumors, squamous cell carcinomas arising in specific locations, and malignancies imaged with non-FDG radiotracers. With the advent of digital PET/CT scanners, PET/MR is expected to partake in future technical developments, such as novel iterative reconstruction techniques and deviceless motion correction for respiration and gross movement in the head and neck region. Owing to the still comparably high costs of PET/MR scanners and facility requirements on the one hand, and the concentration of multidisciplinary head and neck cancer treatment mainly at academic centers on the other hand, a more widespread use of this imaging modality outside major hospitals is currently limited.

Metal artifact reduction in 68Ga-PSMA-11 PET/MRI for prostate cancer patients with hip joint replacement using multiacquisition variable-resonance image combination

BACKGROUND

PET/MRI has a high potential in oncology imaging, especially for tumor indications where high soft tissue contrast is crucial such as genitourinary tumors. One of the challenges for PET/MRI acquisition is handling of metal implants. In addition to conventional methods, more innovative techniques have been developed to reduce artifacts caused by those implants such as the selective multiacquisition variable-image combination (MAVRIC-SL). The aim of this study is to perform a quantitative and qualitative assessment of metal artifact reduction in 68Ga-PSMA-11 PET/MRI for prostate cancer patients with hip joint replacement using a selective MAVRIC-SL sequence for the whole pelvis.

METHODS

We retrospectively analyzed data of 20 men with 37 metal hip implants diagnosed with PCA, staged or restaged by 68Ga-PSMA-11 PET/MRI from June 2016 to December 2017. Each signal cancellation per side or metal implant was analyzed on the reference sequence LAVA-FLEX, as well as T1-weighted fast spin echo (T1w-FSE) sequence and MAVRIC-SL. Two independent reviewers reported on a four-point scale whether abnormal pelvic 68Ga-PSMA-11 uptake could be assigned to an anatomical structure in the tested sequences.

RESULTS

The smallest averaged signal void was observed on MAVRIC-SL sequences with a mean artifact size of 26.17 cm2 (range 12.63 to 42.93 cm2, p < 0.001). The best image quality regarding anatomical assignment of pathological PSMA uptakes in the pelvis by two independent readers was noted for MAVRIC-SL sequences, followed by T1w-FSE with excellent interreader agreement.

CONCLUSIONS

MAVRIC-SL sequence allows better image quality in the surrounding of hip implants by reducing MR signal voids and increasing so the accuracy of anatomical assignment of pathological 68Ga-PSMA-11 uptake in the pelvis over LAVA-FLEX and T1w-FSE sequences.

PET/MRI versus PET/CT in oncology: a prospective single-center study of 330 examinations focusing on implications for patient management and cost considerations

Purpose

PET/MRI has recently been introduced into clinical practice. We prospectively investigated the clinical impact of PET/MRI compared with PET/CT, in a mixed population of cancer patients, and performed an economic evaluation of PET/MRI.

Methods

Cancer patients referred for routine staging or follow-up by PET/CT underwent consecutive PET/CT and PET/MRI, using single applications of [¹⁸F]FDG, [⁶⁸Ga]Ga-DOTANOC, or [¹⁸F]FDOPA, depending on tumor histology. PET/MRI and PET/CT were rated separately, and lesions were assessed per anatomic region; based on regions, per-examination and per-patient accuracies were determined. A simulated, multidisciplinary team meeting served as reference standard and determined whether differences between PET/CT and PET/MRI affected patient management. The McNemar tests were used to compare accuracies, and incremental cost-effectiveness ratios (ICERs) for PET/MRI were calculated.

Results

Two hundred sixty-three patients (330 same-day PET/CT and PET/MRI examinations) were included. PET/MRI was accurate in 319/330 examinations and PET/CT in 277/330 examinations; the respective accuracies of 97.3% and 83.9% differed significantly (P < 0.001). The additional findings on PET/MRI—mainly liver and brain metastases—had implications for patient management in 21/263 patients (8.0%). The per-examination cost was 596.97 EUR for PET/MRI and 405.95 EUR for PET/CT. ICERs for PET/MRI were 14.26 EUR per percent of diagnostic accuracy and 23.88 EUR per percent of correctly managed patients.

Conclusions

PET/MRI enables more appropriate management than PET/CT in a nonnegligible fraction of cancer patients. Since the per-examination cost is about 50% higher for PET/MRI than for PET/CT, a histology-based triage of patients to either PET/MRI or PET/CT may be meaningful.

First Clinicopathologic Evidence of a Non-PSMA-Related Uptake Mechanism for 68Ga-PSMA-11 in Salivary Glands

The intense accumulation of prostate-specific membrane antigen (PSMA) radioligands in salivary glands is still not well understood. It is of concern for therapeutic applications of PSMA radioligands, because therapeutic radiation will damage these glands. A better understanding of the uptake mechanism is, therefore, crucial to find solutions to reduce toxicity. The aim of this study was to investigate whether the accumulation of PSMA-targeting radioligands in submandibular glands (SMGs) can be explained with PSMA expression levels using autoradiography (ARG) and immunohistochemistry (IHC). Methods: All patients gave written informed consent for further utility of the biologic material. The SMG of 9 patients, pancreatic tissue of 4 patients, and prostate cancer (PCA) lesions of 9 patients were analyzed. Tissue specimens were analyzed by means of PSMA-IHC (using an anti-PSMA-antibody and an immunoreactivity score system [IRS]) and ARG using ¹⁷⁷Lu-PSMA-617 (with quantification of the relative signal intensity compared with a PSMA-positive standard). The SUV_max in salivary glands, pancreas, and PCA tissues were quantified in 60 clinical ⁶⁸Ga-PSMA-11 PET scans for recurrent disease as well as the 9 primary tumors selected for ARG and IHC. Results: PCA tissue samples revealed a wide range of PSMA staining intensity on IHC (IRS = 70-300) as well as in ARG (1.3%-22% of standard). This variability on PCA tissue could also be observed in ⁶⁸Ga-PSMA-11 PET (SUV_max, 4.4-16) with a significant correlation between ARG and SUV_max (P < 0.001, R ² = 0.897). On IHC, ARG, and ⁶⁸Ga-PSMA-11 PET, the pancreatic tissue was negative (IRS = 0, ARG = 0.1% ± 0.05%, SUV_max of 3.1 ± 1.1). The SMG tissue displayed only focal expression of PSMA limited to the intercalated ducts on IHC (IRS = 10-15) and a minimal signal on ARG (1.3% ± 0.9%). In contrast, all SMG showed a high ⁶⁸Ga-PSMA-11 accumulation on PET scans (SUV_max 23.5 ± 5.2). Conclusion: Our results indicate that the high accumulation of PSMA radioligands in salivary glands does not correspond to high PSMA expression levels determined using ARG and IHC. These findings provide evidence, that the significant accumulation of PSMA radioligands in SMG is not primarily a result of PSMA-mediated uptake.

Clinical value of 18F-FDG-PET/CT in suspected serious disease with special emphasis on occult cancer

PURPOSE

Suspected serious disease (SSD) is a disease designation often given to patients with one or more non-specific symptoms of severe disease that could be due to cancer; the optimal diagnostic strategy is largely left to the clinician's discretion. Being a sensitive non-invasive whole-body imaging modality ¹⁸F-FDG-PET/CT may have a potential role in this cancer-prevalent group of patients to confirm or refute suspected malignancy. We aimed to investigate the diagnostic value of ¹⁸F-FDG-PET/CT in SSD using long-term follow-up as reference.

METHODS

We retrospectively studied results obtained in all SSD patients referred for ¹⁸F-FDG-PET/CT at a single institution in 2010-2011 retrieving the following clinical data in all patients: journal entries, examinations, and evaluations made from 6 months before the scan and until the latest recorded entry. A true positive PET scan was a positive scan with a subsequently biopsy-confirmed diagnosis of cancer in the same target organ, whereas a false positive scan had no subsequent cancer diagnosis. A true negative PET scan was a negative scan without a cancer diagnosis during follow-up, whereas a false negative PET scan was one with a subsequently confirmed cancer diagnosis.

RESULTS

Ninety-three patients, aged 67 years (range 25-89) were included and followed for up to 7.3 years (median 6). Of these, 21 [22.6% (95% CI 15.3-32.1)] turned out to have cancer. With ¹⁸F-FDG-PET/CT, the sensitivity was 81.0% (95% CI 60.0-92.3), specificity 76.4% (95% CI 65.4-84.7), positive predictive value 50% (95% CI 34.1-65.9), and negative predictive value 93.2% (95% CI 83.8-97.3). Five patients with negative scans were subsequently diagnosed with cancer.

CONCLUSION

Cancer prevalence is substantial among patients with SSD. ¹⁸F-FDG-PET/CT is a promising option in this setting, in particular because a high negative predictive value equals a low incidence of cancer during follow-up. Further studies are needed to establish the role of ¹⁸F-FDG-PET/CT in SSD.

Lymphangioma on 68Ga-NOTA-Evans Blue PET/MRI

A 17-year-old adolescent boy with a history of hypoproteinemia underwent Ga-NEB PET/MRI to evaluate possible lymphatic disorders suggested by FDG PET/CT imaging. The images revealed multiple lesions with increased Ga-NEB uptake and high signal on T2-weighted images, consistent with likely lymphatic disorder. Histopathological examination from biopsied specimen confirmed lymphangioma.

Whole-Body 68Ga-DOTANOC PET/MRI Versus 68Ga-DOTANOC PET/CT in Patients With Neuroendocrine Tumors: A Prospective Study in 28 Patients

PURPOSE

The aim of this study was to assess the diagnostic performance of simultaneous whole-body Ga-DOTANOC PET/MRI compared with Ga-DOTANOC PET/CT for detection of distant metastatic disease in patients with well-differentiated neuroendocrine tumors (NETs).

METHODS

Patients with histologically proven, well-differentiated NET (G1 or G2) were included in this prospective, institutional review board-approved study. Patients underwent Ga-DOTANOC PET/CT and subsequent Ga-DOTANOC PET/MRI after a single tracer injection on the same day for staging or restaging purposes. Images were evaluated for the presence of NET lesions by 2 rater teams, each consisting of a nuclear medicine physician and a radiologist, in an observer-blinded fashion. Overall agreement, accuracy, sensitivity, and specificity, relative to a composite reference standard (consensus review including follow-up data), were calculated.

RESULTS

Between July 2014 and June 2016, 28 patients were enrolled. Overall agreement and accuracy between the 2 rater teams were 91.7% (95% confidence interval [CI], 87.5%-95.9%) and 97% (95% CI, 94.4%-99.6%) for PET/MRI and 92.3% (95% CI, 88.3%-96.3%) and 94.6% (95% CI, 91.2%-98.1%) for PET/CT, respectively (P = 1.00).Overall, PET/MRI reached 89.8% sensitivity (95% CI, 77.8%-96.6%) and 100% specificity (95% CI, 97%-100%); PET/CT showed 81.6% sensitivity (95% CI, 68%-91.2%) and 100% specificity (95% CI, 97%-100%) for the detection of metastatic disease in NETs.

CONCLUSIONS

Whole-body Ga-DOTANOC PET/MRI appears to be comparable to Ga-DOTANOC PET/CT for lesion detection in patients with well-differentiated NETs.

Combined PET/MRI: Global Warming-Summary Report of the 6th International Workshop on PET/MRI, March 27-29, 2017, Tübingen, Germany

The 6th annual meeting to address key issues in positron emission tomography (PET)/magnetic resonance imaging (MRI) was held again in Tübingen, Germany, from March 27 to 29, 2017. Over three days of invited plenary lectures, round table discussions and dialogue board deliberations, participants critically assessed the current state of PET/MRI, both clinically and as a research tool, and attempted to chart future directions. The meeting addressed the use of PET/MRI and workflows in oncology, neurosciences, infection, inflammation and chronic pain syndromes, as well as deeper discussions about how best to characterise the tumour microenvironment, optimise the complementary information available from PET and MRI, and how advanced data mining and bioinformatics, as well as information from liquid biomarkers (circulating tumour cells and nucleic acids) and pathology, can be integrated to give a more complete characterisation of disease phenotype. Some issues that have dominated previous meetings, such as the accuracy of MR-based attenuation correction (AC) of the PET scan, were finally put to rest as having been adequately addressed for the majority of clinical situations. Likewise, the ability to standardise PET systems for use in multicentre trials was confirmed, thus removing a perceived barrier to larger clinical imaging trials. The meeting openly questioned whether PET/MRI should, in all cases, be used as a whole-body imaging modality or whether in many circumstances it would best be employed to give an in-depth study of previously identified disease in a single organ or region. The meeting concluded that there is still much work to be done in the integration of data from different fields and in developing a common language for all stakeholders involved. In addition, the participants advocated joint training and education for individuals who engage in routine PET/MRI. It was agreed that PET/MRI can enhance our understanding of normal and disrupted biology, and we are in a position to describe the in vivo nature of disease processes, metabolism, evolution of cancer and the monitoring of response to pharmacological interventions and therapies. As such, PET/MRI is a key to advancing medicine and patient care.

Clinical performance of 68Ga-PSMA-11 PET/MRI for the detection of recurrent prostate cancer following radical prostatectomy

PURPOSE

Sensitive visualization of recurrent prostate cancer foci is a challenge in patients with early biochemical recurrence (EBR). The recently established ⁶⁸Ga-PSMA-11 PET/CT has significantly improved the detection rate with published values of up to 55% for patients with a serum PSA concentration between 0.2-0.5 ng/mL. The increased soft tissue contrast in the pelvis using simultaneous ⁶⁸Ga-PSMA-11 PET/MRI might further improve the detection rate in patients with EBR and low PSA values over PET/CT.

METHODS

We retrospectively analyzed a cohort of 56 consecutive patients who underwent a ⁶⁸Ga-PSMA-11 PET/MRI for biochemical recurrence in our institution between April and December 2016 with three readers. Median PSA level was 0.99 ng/mL (interquartile range: 3.1 ng/mL). Detection of PSMA-positive lesions within the prostate fossa, local and distant lymph nodes, bones, or visceral organs was recorded. Agreement among observers was evaluated with Fleiss's kappa (k).

RESULTS

Overall, in 44 of 56 patients (78.6%) PSMA-positive lesions were detected. In four of nine patients (44.4%) with a PSA < 0.2 ng/mL, suspicious lesions were detected (two pelvic and one paraaortic lymph nodes, and two bone metastases). In eight of 11 patients (72.7%) with a PSA between 0.2 and < 0.5 ng/mL, suspicious lesions were detected (two local recurrences, six lymph nodes, and one bone metastasis). Five out of 20 patients with a PSA < 0.5 ng/mL had extrapelvic disease. In 12 of 15 patients (80.0%) with a PSA between 0.5 and < 2.0 ng/mL, suspicious lesions were detected (four local recurrences, nine lymph nodes, and four bone metastases). In 20 of 21 patients (95.2%) with a PSA >2.0 ng/mL, suspicious lesions were detected. The overall interreader agreement for cancer detection was excellent (κ = 0.796, CI 0.645-0.947).

CONCLUSIONS

Our data show that ⁶⁸Ga-PSMA-11 PET/MRI has a high detection rate for recurrent prostate cancer even at very low PSA levels <0.5 ng/mL. Furthermore, even at those low levels extrapelvic disease can be localized in 25% of the cases and local recurrence alone is seen only in 10%.