Optimising TNM Staging of Patients with Prostate Cancer Using WB-MRI

MRI fat fraction imaging of nodal and bone metastases in prostate cancer

KEY POINTS

• Characterisation and quantification of tissue fat on MRI can be used to provide information on disease processes. • Fat in bone and lymph nodes up until recently have not been exploited for diagnostic purposes or response monitoring in prostate cancer. • Fat imaging on MRI using Dixon/PDFF sequences has the potential to add clinical value in the future but prospective data is needed.

Whole‑body MRI for metastatic workup in patients diagnosed with cancer

Early diagnosis and appropriate staging workup are crucial for cancer patients. Whole-body magnetic resonance imaging (WB-MRI) has been proposed as another practical whole-body approach for assessing local invasiveness and distant metastases in patients newly diagnosed with cancer. The current study aimed to evaluate the efficacy of WB-MRI in assessing metastasis in patients newly diagnosed with cancer using histopathologic data as the reference method. A prospective observational study was performed from April 2018 to July 2020. MRI sequences were utilized to acquire anatomical and functional images in three orthogonal planes. The discovery was classified as nodal, skeletal and visceral metastases. Patient-based analysis was used for visceral metastasis and region-based for skeletal, systemic and lymph node metastases. A total of 43 consecutive patients (mean age, 56±15.2 years) were assessed successively. In 41 patients, there was a concordance between the WB-MRI and histological confirmation. The most prevalent site of metastasis was the skeletal system (18 patients). There were 12 individuals with liver metastasis, 10 with lung metastasis and 4 with peritoneal metastasis, with just one brain metastatic lesion found. On WB-MRI, 38 lymph node groups were deemed positive. Out of the total, 66 skeletal locations contained metastases. The accuracy of WB-MRI for nodal, skeletal and visceral metastases was (98.45, 100 and 100%, respectively). In conclusion, WB-MRI in three orthogonal planes, including the diffusion-weighted MRI with background body signal suppression sequence, may be utilized efficiently and accurately for assessing metastasis staging and may thus be utilized in patients with newly diagnosed cancer.

The future of PSMA PET and WB MRI as next-generation imaging tools in prostate cancer

Radiolabelled prostate-specific membrane antigen (PSMA)-based PET-CT has been shown in numerous studies to be superior to conventional imaging in the detection of nodal or distant metastatic lesions. ⁶⁸Ga-PSMA PET-CT is now recommended by many guidelines for the detection of biochemically relapsed disease after radical local therapy. PSMA radioligands can also function as radiotheranostics, and Lu-PSMA has been shown to be a potential new line of treatment for metastatic castration-resistant prostate cancer. Whole-body (WB) MRI has been shown to have a high diagnostic performance in the detection and monitoring of metastatic bone disease. Prospective, randomized, multicentre studies comparing ⁶⁸Ga-PSMA PET-CT and WB MRI for pelvic nodal and metastatic disease detection are yet to be performed. Challenges for interpretation of PSMA include tracer trapping in non-target tissues and also urinary excretion of tracers, which confounds image interpretation at the vesicoureteral junction. Additionally, studies have shown how long-term androgen deprivation therapy (ADT) affects PSMA expression and could, therefore, reduce tracer uptake and visibility of PSMA⁺ lesions. Furthermore, ADT of short duration might increase PSMA expression, leading to the PSMA flare phenomenon, which makes the accurate monitoring of treatment response to ADT with PSMA PET challenging. Scan duration, detection of incidentalomas and presence of metallic implants are some of the major challenges with WB MRI. Emerging data support the wider adoption of PSMA PET and WB MRI for diagnosis, staging, disease burden evaluation and response monitoring, although their relative roles in the standard-of-care management of patients are yet to be fully defined.

Whole-body MRI-based multivariate prediction model in the assessment of bone metastasis in prostate cancer

PURPOSE

A whole-body MRI (WB-MRI) including T1, short time inversion recovery (STIR), diffusion-weighted imaging (high b value) was applied in our center for the detection of bone metastasis in prostate cancer (PCa) patients. We intended to assess the diagnostic performance of this examination.

METHODS

547 cases of PCa patients with higher risk of metastasis were referred to bone scintigraphy with SPECT/CT (BS + SPECT/CT) and whole-body MRI in Shanghai Changhai Hospital. Best valuable comparator (BVC) was applied for the final diagnosis of metastasis. A panel of radiologists interpreted the results. Decision curve analysis (DCA) and receiver operating characteristic curve (ROC) analysis were applied.

RESULTS

Bone metastasis was diagnosed in 110 cases, and others were non-metastatic by BVC. The area under the receiver operating characteristic curve (AUC) was higher in WB-MRI (0.778) than BS + SPECT/CT (0.634, p < 0.001). A WB-MRI-based prediction model was established with AUC of 0.877. Internal validation showed that the predictive model was well-calibrated. The DCA demonstrated that the model had higher net benefit than the BS + SPECT/CT-based model.

CONCLUSION

WB-MRI is more effective in identifying metastasis in PCa patients than BS + SPECT/CT. The prediction model combined WB-MRI with clinical parameters may be a promising approach to the assessment of metastasis.

Two cases of oligometastatic castration-resistant prostate cancer detected by diffusion-weighted whole-body imaging with background body signal suppression

INTRODUCTION

Treatment for oligometastasis in prostate cancer has changed from systemic therapy to metastatic lesion-targeted therapy. Early detection of metastatic lesions and assessment of the treatment response have become very important. Therefore, we started to perfume assessments with whole-body magnetic resonance imaging, especially diffusion-weighted imaging with background body signal suppression, as a modality to detect metastasis in patients with prostate cancer.

CASE PRESENTATION

We encountered two cases of castration-resistant prostate cancer in which oligometastasis was detected by diffusion-weighted imaging with background body signal suppression. Metastasis-directed therapy was initiated for to treat the lesions in each case. The treatment was effective for disease control and symptom relief. Diffusion-weighted imaging with background body signal suppression could detect new lesions at an early phase and delineate changes in lesions immediately after therapy.

CONCLUSION

Diffusion-weighted imaging with background body signal suppression enables early decision-making for metastasis-directed therapy compared with conventional imaging modalities. Further, metastasis-directed therapy targeting oligometastatic lesions detected by diffusion-weighted imaging with background body signal suppression may improve patients' overall survival and quality of life.

Belgian Radiology Research in Full Power!

In Belgium, there has always been a strong tradition to foster radiology and imaging research. The former Royal Belgian Society of Radiology (RBSR-KBVR-SRBR)—after the merger with the Consilium and NUR, now the Belgian Society of Radiology (BSR-BVR-SBR)—has persistently been one of the driving forces of support to individuals who wanted to innovate and put Belgian radiology research at the forefront.