Biparametric MRI prior to Radical Radiation Therapy for Prostate Cancer in a Caribbean Population: Implications for Risk Group Stratification and Treatment.

Purpose: To assess risk-group migration and subsequent management change following biparametric MRI using a risk-stratified approach in a group of Caribbean men with prostate adenocarcinoma being offered external beam radiation therapy (EBRT). Materials and Methods: This retrospective study assessed the biparametric MRI findings in men who opted for EBRT from January 2018 to June 2019 (n = 79; mean age, 67.9 years ± 6.2 [standard deviation]). Serum prostate-specific antigen level, digital rectal examination findings, histologic grade group (GG) from transrectal US-guided biopsy, prior androgen deprivation therapy (ADT), and any prior CT results were used to stratify patients into low-, intermediate-, and high-risk groups, according to the National Comprehensive Cancer Network risk categories. Risk-group stratification prior to MRI separated patients into low- (seven of 79 [8.9%]), intermediate- (36 of 79 [45.6%]) and high-risk (36 of 79 [45.6%]) groups. Following MRI, any risk group (low, intermediate, high, nodal involvement, and metastatic disease) or oncologic management changes were recorded. Multivariable binary logistic regression analyses were used to assess predictor of upgrade status, with adjustment for demographic covariates jointly. Results: Following MRI, 30 of 79 (38.0%) patients had risk-group upshifts compared with their original assessment. Patients were recategorized into low risk (one of 79, 1.3%), intermediate risk (19 of 79, 24.1%), high risk (51 of 79, 64.6%), nodal involvement (one of 79, 1.3%), and metastatic disease (seven of 79, 8.9%). From the original groupings, there were six of seven (85.7%) from the low group, 18 of 36 (50.0%) from the intermediate group, and six of 36 (16.7%) from the high group that had risk group upward shifts. There was no association with GG: GG2 versus GG1, P = .53; GG3 versus GG1, P = .98; or prior ADT (P = .37) and the adjusted odds of risk-group upshifts. MRI findings resulted in treatment plan modification for 39 of 79 (49.4%) men overall. Conclusion: Prostate MRI should be considered for patients in high-risk populations prior to EBRT because upstaging from MR image assessment may have implications for modification of treatment.Keywords: MR-Imaging, Prostate, Radiation Therapy© RSNA, 2020See the commentary by Davenport and Shankar in this issue.

Plexiform neurofibroma of the wrist: imaging features and when to suspect malignancy.

Plexiform neurofibromas are essentially pathognomonic for neurofibromatosis type 1 (NF1), occurring when there is diffuse involvement along a nerve segment and its branches. Transformation into a malignant peripheral nerve sheath tumour (MPNST) is a major cause of mortality in NF1 patients. These tumours are highly aggressive and particularly difficult to diagnose in NF1 patients due to the clinical overlap between benign and malignant lesions. We present a case of a plexiform neurofibroma and discuss the typical imaging characteristics on ultrasound, CT, and MRI, including the target sign and continuity with the parent nerve. Certain imaging features should raise suspicion for malignancy however, these modalities may not always reliably differentiate between benign and malignant lesions. Recent studies show a very high negative predictive value for FDG-PET making it quite useful in excluding malignancy. In positive scans, PET/CT aids in guiding biopsy to the most metabolically active area of the tumour.