Transcutaneous high-intensity focused ultrasound and irradiation: an organ-preserving treatment of cancer in a solitary testis

Abstract

Objectives: The aim of this study was to determine the feasibility and safety of transcutaneous ablation of human testicular tissue by high-intensity focused ultrasound (HIFU).

Methods: Transcutaneous ablation of human testicular tissue by HIFU was performed with equipment previously developed for transrectal prostate ablation. This device utilizes a piezoceramic transducer operating at 4.0 MHz with a site-intensity of 1,600-2,000 W/cm2. To study the histological impact of transcutaneous HIFU, tests of 4 patients with prostate cancer were subjected to transcutaneous HIFU-therapy prior to scrotal orchiectomy in a phase I trial. In a phase II clinical trial, 4 patients with the typical sonographic pattern of a tumor in a solitary testis were treated with transcutaneous HIFU as a minimally invasive organ-preserving approach followed by a 6 weeks' course of prophylactic irradiation of the testis with 20 Gy. In all 4 patients, the contralateral testis had been previously removed for testis cancer.

Results: Histologically, HIFU-treated areas exhibited signs of cellular necrosis in all cases (n = 4). The border between viable and necrotic tissue was extremely sharp comprising only 5-7 cell layers. In the phase II clinical study, we aimed to ablate the entire cancer in a single therapeutic HIFU session. HIFU treatment was performed under general anesthesia. As negative side effects we observed a cutaneous thermolesion in 1 individual. One patient refused to undergo postoperative irradiation and developed a local failure. This patient underwent radical orchiectomy. Another patient received two cycles of chemotherapy for a single suspicious retroperitoneal lymph node diagnosed 6 months after HIFU therapy. Three patients are tumor-free with a follow-up of 16, 23 and 31 months, respectively.

Conclusions: This study demonstrates the feasibility and safety of transcutaneous testicular tissue ablation by HIFU. Despite the major drawback of this technique, i.e. that no tumor histology is obtained, we believe that transcutaneous HIFU followed by irradiation has the potential to be established as a minimally invasive treatment alternative to organ-preserving surgery for tumors in a solitary testis.