Characterization of the histological response to the Butterfly Prostatic Retraction Device in patients with benign prostatic hyperplasia

Purpose: The Butterfly Prostatic Retraction Device (“Butterfly”) is a permanent nitinol implant for benign prostatic hyperplasia. This study examines the chronic response of prostate tissue to the Butterfly in histological specimens from patients in the Butterfly pilot clinical study. Methods: Retrospective qualitative and semi-quantitative review of histological specimens of seven (7) patients who participated in the Butterfly pilot clinical study. Patients had at least 1-month implantation with the Butterfly prior to implant removal and TURP. Tissue samples were graded by two pathologists. Results: Four out of six patients had IPSS decreased from baseline. All seven patients’ samples had signs of chronic inflammation; one demonstrated acute inflammation and one demonstrated fibrosis. In three cases, intraglandular calcification was identified. There was no ischemic necrosis induced by the implant, and no encrustation, urethral edema, or cellular atypia was noted. Conclusion: The Butterfly demonstrated an overall favorable safety profile in terms of tissue response. This study demonstrates that there is no significant tissue reaction in the prostatic urethra due to presence of Butterfly device.