V08-08: A novel case combining PSMA based (18)F-DCFPyL PET/CT and MRI/ultrasound fusion guided biopsy to assess local recurrence of prostate cancer

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INTRODUCTION

11-31% of radical prostatectomies (RP) are associated with positive surgical margins (PSM) depending on approach and pre-operative risk.1 Differentiating residual normal tissue from persistent or recurrent cancer in the setting of biochemical recurrence can be challenging. Modern MRI studies have reported 94% sensitivity and 100% specificity for detecting local recurrence in lesions 7.6mm or greater in length.2 If the tissue in question is detected on MRI, MRI/ultrasound fusion biopsy (fusion biopsy) of these lesions have demonstrated per patient cancer detection rates of 80%.3 PSMA based F:18 PET CT has shown promise at detecting recurrence, with optimal cut-off PSA value to predict a positive 18F-DCFBC scan reported to be as low as 0.78 ng/mg.4 The combination of these modalities can be used to more accurately differentiate benign tissue from residual or recurrent disease.

METHODS

We present a case of a patient enrolled on National Institutes of Health (NIH) protocol 2017-C-0109, (18)F-DCFPyL PET/CT (DCFPyL) in High Risk and Recurrent Prostate Cancer. This 73M underwent RP with PSM with invasive carcinoma at margins. Post-operative PSA was detectable. He was initially treated with salvage radiation and later referred to the NIH for continued PSA rise. Metastatic workup with conventional imaging was negative. Between July-September 2018, he underwent MRI prostate, DCFPyL, and fusion biopsy.

RESULTS

MRI: 2.6 cm lesion at inferior-mid portion of the prostatectomy bed. Score: Likely residual normal prostate tissue. 0.8 cm tissue lesion at 2 o’clock direction at mid-prostatectomy bed. Score: Low-moderate.1.6 cm lesion right superior portion of the prostatectomy bed. Score: Moderate. Seminal vesicles (SV) present bilaterally with a subtle focus at DCE MRI in the right seminal vesicles. No bony or nodal disease. DCFPyL: Avid focus at the right superior aspect of the prostatectomy bed suggesting disease recurrence. Fusion biopsy pathology: Differentiated adenocarcinoma with treatment effect at the right superior portion of the prostatectomy bed that corresponded with the DCFPyL. Differentiated adenocarcinoma in remnant right SV. Remaining lesions: benign prostate tissue.

CONCLUSION

Combining DCFPyL and fusion biopsy can more accurately differentiate remnant benign prostate tissue from residual or recurrent local disease and help guide management.

Funding: none