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To examine the safety and efficacy of microwave tissue coagulation (MTC) for prostate cancer and assess its use in lesion-targeted focal therapy in a non-clinical study and a clinical phase II trial.In the non-clinical study using MicrotazeThe region of coagulative necrosis was predictable by monitoring of ultrasonically visible vaporization; thus, by placing the MTC needle at a certain distance, we were able to perform a safe procedure without adverse events affecting the surrounding organs. Based on the non-clinical study, which used various combinations of output and irradiation time, MTC with 30-W output for 60-s irradiation was selected for the prostate. Based on the predictable necrosis, the therapeutic plan (where to place the MTC needle to achieve complete ablation of the target and how many sessions) was strictly determined per patient. There were no serious adverse events in any patient and only temporary urinary symptoms related to MTC therapy were observed. Furthermore, post-treatment satisfaction was very high. All preoperative MRI-visible lesions disappeared, and PSA decreased by 55% 6 months after surgery.Microwave tissue coagulation may be an option for lesion-targeted focal therapy for prostate cancer.

A 23-year-old man presented with complaints of macrohematuria and hematospermia and was referred to our hospital for further examination. Magnetic resonance imaging revealed a round 30 × 25 mm tumor in the right peripheral zone; hence, a rare prostate tumor was suspected. Grayscale transrectal ultrasonography (TRUS) was performed using the Aplio-i800 PVL-715RST-transducer and revealed a well-defined round tumor. Although regular color Doppler flow imaging could not detect internal blood flow, superb microvascular imaging (SMI) identified the low-velocity blood flow in the tumor. Based on the results of a TRUS-guided targeted biopsy assisted by SMI, the patient was diagnosed with stromal sarcoma. He underwent total pelvic exenteration with construction of ileal conduit and colostomy, the tumor was finally diagnosed as prostate stromal sarcoma (PSS). Since PSS is a rare malignant prostate tumor, reports on the characteristic findings in imaging tests are scarce. To the best of our knowledge, this study reports the first case in which a poor internal blood flow was detected in PSS, but not through regular color Doppler flow imaging. SMI revealed that the blood flow signal to the PSS was relatively poor; however, its definite presence was confirmed, suggesting a malignant disease with relatively poor blood supply and the findings of SMI would assist the adequate targeted biopsy-sampling from the presence site of viable cells with the blood supply.