Prospective evaluation of 68Gallium-prostate-specific membrane antigen positron emission tomography/computed tomography for preoperative lymph node staging in prostate cancer

OBJECTIVES

To assess the accuracy of 68Gallium-prostate-specific membrane antigen (68Ga-PSMA) positron emission tomography/computed tomography (PET/CT) for lymph node (LN) staging in intermediate- and high-risk prostate cancer (PCa).

MATERIALS AND METHODS

From April to October 2015, 30 patients with intermediate- (n = 3) or high-risk (n = 27) PCa were prospectively enrolled. Patients underwent preoperative 68Ga-PSMA PET/CT. Both visual and semi-quantitative analyses were undertaken. Subsequently, all patients underwent radical prostatectomy (RP) with an extended pelvic lymph node dissection. The sensitivity, specificity, and positive (PPV) and negative predictive value (NPV) for LN status of 68Ga-PSMA were calculated using histopathology as reference.

RESULTS

Eleven patients (37%) had lymph node metastases (LNMs); 26 LNMs were identified in the 11 patients. Patient analysis showed that 68Ga-PSMA PET/CT had a sensitivity of 64% for the detection of LNMs, its specificity was 95%, the PPV was 88%, and the NPV was 82%. In total, 180 LN fields were analysed. In the LN-region-based analysis, the sensitivity of 68Ga-PSMA PET/CT for detection of LNMs was 56%, the specificity was 98%, the PPV was 90% and the NPV was 94%. The mean size of missed LNMs was 2.7 mm. Receiver-operating characteristic curve analysis showed a high accuracy of maximum standardized uptake value (SUV_max ) for the detection of LNMs, with an area under the curve of 0.915 (95% confidence interval 0.847-0.983); the optimum SUV_max was 2.0.

CONCLUSIONS

In patients with intermediate- to high-risk PCa, 68Ga-PSMA PET/CT had a high specificity and a moderate sensitivity for LNM detection. 68Ga-PSMA PET/CT had the potential to replace current imaging for LN staging of patients with PCa scheduled for RP.

Prospective Comparison of 18F-Fluoromethylcholine Versus 68Ga-PSMA PET/CT in Prostate Cancer Patients Who Have Rising PSA After Curative Treatment and Are Being Considered for Targeted Therapy

In prostate cancer with biochemical failure after therapy, current imaging techniques have a low detection rate at the prostate-specific antigen (PSA) levels at which targeted salvage therapy is effective. (11)C-choline and (18)F-fluoromethylcholine, though widely used, have poor sensitivity at low PSA levels. (68)Ga-PSMA (Glu-NH-CO-NH-Lys-(Ahx)-[(68)Ga-N,N'-bis[2-hydroxy-5-(carboxyethyl)benzyl]ethylenediamine-N,N'-diacetic acid]) has shown promising results in retrospective trials. Our aim was to prospectively compare the detection rates of (68)Ga-PSMA versus (18)F-fluoromethylcholine PET/CT in men who were initially managed with radical prostatectomy, radiation treatment, or both and were being considered for targeted therapy.

METHODS

A sample of men with a rising PSA level after treatment, eligible for targeted treatment, was prospectively included. Patients on systemic treatment were excluded. (68)Ga-PSMA, (18)F-fluoromethylcholine PET/CT, and diagnostic CT were performed sequentially on all patients between January and April 2015, and the images were assessed by masked, experienced interpreters. The findings and their impact on management were documented, together with the results of histologic follow-up when feasible.

RESULTS

In total, 38 patients were enrolled. Of these, 34 (89%) had undergone radical prostatectomy and 4 (11%) had undergone radiation treatment. Twelve (32%) had undergone salvage radiation treatment after primary radical prostatectomy. The mean PSA level was 1.74 ± 2.54 ng/mL. The scan results were positive in 26 patients (68%) and negative with both tracers in 12 patients (32%). Of the 26 positive scans, 14 (54%) were positive with (68)Ga-PSMA alone, 11 (42%) with both (18)F-fluoromethylcholine and (68)Ga-PSMA, and only 1 (4%) with (18)F-fluoromethylcholine alone. When PSA was below 0.5 ng/mL, the detection rate was 50% for (68)Ga-PSMA versus 12.5% for (18)F-fluoromethylcholine. When PSA was 0.5-2.0 ng/mL, the detection rate was 69% for (68)Ga-PSMA versus 31% for (18)F-fluoromethylcholine, and when PSA was above 2.0, the detection rate was 86% for (68)Ga-PSMA versus 57% for (18)F-fluoromethylcholine. On lesion-based analysis, (68)Ga-PSMA detected more lesions than (18)F-fluoromethylcholine (59 vs. 29, P < 0.001). The tumor-to-background ratio in positive scans was higher for (68)Ga-PSMA than for (18)F-fluoromethylcholine (28.6 for (68)Ga-PSMA vs. 9.4 for (18)F-fluoromethylcholine, P < 0.001). There was a 63% (24/38 patients) management impact, with 54% (13/24 patients) being due to (68)Ga-PSMA imaging alone. Histologic follow-up was available for 9 of 38 patients (24%), and 9 of 9 (68)Ga-PSMA-positive lesions were consistent with prostate cancer ((68)Ga-PSMA was true-positive). The lesion positive on (18)F-fluoromethylcholine imaging and negative on (68)Ga-PSMA imaging was shown at biopsy to be a false-positive (18)F-fluoromethylcholine finding ((68)Ga-PSMA was true-negative).

CONCLUSION

In patients with biochemical failure and a low PSA level, (68)Ga-PSMA demonstrated a significantly higher detection rate than (18)F-fluoromethylcholine and a high overall impact on management.

Flow-induced separation in wall turbulence

One of the defining characteristics of turbulence is its ability to promote mixing. We present here a case where the opposite happens-simulation results indicate that particles can separate near the wall of a turbulent channel flow, when they have sufficiently different Schmidt numbers without use of any other means. The physical mechanism of the separation is understood when the interplay between convection and diffusion, as expressed by their characteristic time scales, is considered, leading to the determination of the necessary conditions for a successful separation between particles. Practical applications of these results can be found when very small particles need to be separated or removed from a fluid.

Vision outcomes and major complications after endovascular coil embolization of ophthalmic segment aneurysms

BACKGROUND AND PURPOSE

As aneurysms arising from the ophthalmic segment of the internal carotid artery increase in size, they can compress the optic nerve, prompting patients to present with visual disturbances. The purpose of this article is to describe the clinical and angiographic results with an emphasis on visual outcomes following the endovascular treatment of ophthalmic segment ICA aneurysms.

MATERIALS AND METHODS

The records of 1254 patients who presented for endovascular treatment of a cerebral aneurysm were retrospectively reviewed to identify 65 consecutive patients who underwent coil embolization of an ophthalmic segment ICA aneurysm. The clinical records, treatment reports, and imaging were reviewed with a focus on visual outcomes.

RESULTS

Twenty-two of the 65 patients (34%) who presented for treatment of an ophthalmic aneurysm reported a visual disturbance at presentation. Fifteen of the 22 patients (68%) experienced an improvement in their symptoms after treatment. Overall, patients with visual symptoms were significantly more likely to benefit from treatment than to have a decline in vision (P = .03). The overall morbidity was 4%, and mortality was 0%. The retreatment rate was high at 30%, though this was disproportionately weighted by an 86% retreatment rate in patients with ruptured aneurysms.

CONCLUSIONS

Patients with visual symptoms attributable to ophthalmic segment ICA aneurysms undergoing endovascular coil embolization were statistically more likely to experience an improvement in their vision than to have worsening or unchanged vision. Coiling was associated with a low morbidity rate, though an elevated retreatment rate.