Endoscopic management of large prostate volumes (PV) > 80–100 ml remains a clinical scenario with limited available treatment options. Although electrode vaporization is less reported than laser surgery, transurethral electro vaporization of the prostate (TUVP) demonstrated advantages of low bleeding risk and no TUR syndrome. However, there are no prospective randomized trials to compare prostate vaporization to resection in prostates larger than 80ml. In 2018, the new oval-shaped electrode (Olympus, Japan) was developed as a second-generation TUVP with improved efficacy of vaporization of prostate tissue. We evaluated the efficacy of this novel oval electrode for large benign prostatic enlargement (BPE) of more than 100ml.

106 consecutive patients underwent second-generation TUVP with the oval-shaped electrode (Figs. 1A and 1B) between July 2018 and July 2020. Six patients (2 prostate cancer, 3 dementia and 1 in terminal stages of non-prostate cancer) were excluded because of lack of ability to complete outcome measures. The remaining 100 patients were enrolled in this study. Prostate volumes were measured by abdominal ultrasound scan or prostate MRI scan.
Surgical indications were as follows; the presence of moderate to severe LUTS (International Prostate Symptoms Score (IPSS) >7) despite proper medication, maximum flow rate (Qmax) <15 mL/s, persistent or recurrent urinary retention or bladder stones, or post-void residual urine volume (PVR) >100 ml. The patients with PSA ≥10 ng/ml were recommended to undergo prostate MRI and subsequently all patients with MRI showing suspected prostate cancer were recommended to undergo needle biopsy before TUVP.
The patients’ characteristics and treatment outcomes were retrospectively compared between patients with prostate volume <100ml and ≥100ml. Haemoglobin (Hb) was measured at pre-operative baseline and at 1 POD (post-operative day). Main treatment outcome were measured by IPSS, IPSS Quality of Life Index (IPSS-QoL), overactive bladder symptom score (OABSS), the Benign Prostatic Hyperplasia Impact Index (BII), uroflowmetry tests (voided volume and Qmax) and PVR at pre-operative baseline and 1, 3 and 6 POM (post-operative months). PSA serum value was also evaluated at pre-operative baseline and 3 POM.
The OABSS, originally developed in Japan, is a 4-item questionnaire that expresses OAB symptoms on a single scale. The OABSS question items address the following individual symptoms: daytime frequency, nocturia, urgency, and urgency incontinence. Gotoh et al. reported that the OABSS was useful for assessing the effects of treatment on OAB symptoms and was responsive to treatment-related changes. The BII, developed by the AUA, assesses the impact of BPH symptoms on patient health and functioning. The BII is a self-administered questionnaire with 4 questions about urinary problems during the past month regarding physical discomfort, worry about health, how bothersome symptoms are, and whether the symptoms are interfering with doing usual activities.

Operative procedure
A preoperative antibiotic was administered, and spinal or general anesthesia was applied. The patient was placed in the lithotomy position and sterile draped. A 26.5-Fr continuous flow resectoscope (30° cystoscopic lens) was inserted into the urethra with the obturator. An oval-shaped electrode (Olympus, Japan) was used for vaporization of the prostate. Normal saline was irrigated with a 26.5-Fr resectoscope with the transurethral resection in saline system. After identifying the ureteral orifice, the verumontanum and external urethral sphincter were identified, and the vaporisation procedure started with the creation of a working space at 5 and 7 o’clock. Then, the median and lateral lobes were vaporized. Vaporization was carried out with cutting setting in TURis system. To minimize bleeding through the procedures, the coagulation setting could rapidly be deployed with the same electrode.

Among the 100 cases, 41 patients had prostate volume more than 100ml and the remaining 59 cases had prostate volume less than 100ml. The average ages were 75.8±7.4 and 74.8±6.9 years-old and average prostate volumes were 75.1±49.3 and 137.6±33.4 ml in patients with prostate <100ml and ≥100ml, respectively. Twenty four and seventeen patients were catheterised pre-operatively due to urinary retention in patients with prostates <100ml and ≥100ml, respectively, there was no significant difference in urinary retention rate between the 2 groups (40.7% and 41.5%).
Average operation time for prostate volumes ≥100ml (123.7±25.1 mins) was significantly higher than <100ml (99.2±25.1 mins, P<0.001). The duration of post-operative catheter placement and hospital-stay period of prostate volume ≥100ml (3.1±1.3 days and 5.6±2.3 days, respectively) were not different from prostate volume <100ml (2.7±1.2 days and 5.0±2.4 days, respectively) (not significant (N.S.)). 
Qmax significantly increased and PVR significantly decreased after surgery in both the PV≥100ml and <100ml groups (at least P<0.05, pre-operation compared with each of 1,3 and 6 POM). Catheter free status after surgery was achieved in 18/24 and 14/17 pre-operative retention cases in patients with <100ml and ≥100ml, respectively. Four of 17 patients with PV≥100ml needed a second TUVP because of persisting urinary retention and all 4 cases then obtained catheter free status. 
IPSS, IPSS-QoL, OABSS and BII scores significantly lower after surgery in both ≥100ml and <100ml groups (at least P<0.01, pre-operation vs 1,3 and 6 POM). 
Pre-operative Hb, 13.6±1.4 g/dL (PV <100ml) and 13.6±1.9 g/dL (PV ≥100ml), slightly declined to 13.1±1.3 g/dL (PV <100ml) and 13.1±1.7 g/dL (PV ≥100ml) at 1 POD). There was no significant difference in post-operative Hb after TUVP, which was 97.0±5.4% of baseline for PV <100ml and 96.9±6.1% for PV ≥100ml. Serum PSA values reduced by almost half at 3POM compared to pre-operation levels in both the ≥100ml and <100ml groups (P<0.001). 
In terms of post-operative complications, post-operative fever arose in 7 cases of PV ≥100ml and 14 cases of <100ml (N.S.). There were 2 cases of septic shock needing catecholamine therapy. Post-operative bleeding (prolonged gross hematuria more than 3 days after TUVP) occurred in 7 cases of ≥100ml and 14 cases of <100ml (N.S.). One case of PV ≥100ml needed return to theatre for transurethral coagulation and the rest of them were treated by conservative treatment. No blood transfusion was needed and no TUR syndrome occurred.

This preliminary study showed the high efficacy and reliable safety of TUVP for treating substantial prostatic enlargement, as well as mild-moderate enlargement. Voiding and storage symptoms, derived from IPSS, OABSS and BII, clearly and significantly improved after TUVP. 32 of 41 cases of urinary retention achieved catheter-free status after first TUVP. This study also found low severity of Hb decrease after surgery, indicating less bleeding during surgery, and fewer surgical complications in substantially enlarged prostates (more than 100ml). These observations suggest that TUVP can be considered a first line option for any size prostate undergoing interventional therapy. The hospital stay duration and postoperative catheter duration for PV more 100ml did not differ significantly from for smaller prostates, also indicating the clinical feasibility of TUVP for any size of gland.

This is first report of efficacy of TUVP on large BPE of more than 100ml. TUVP is clinically effective for the relief of lower urinary tract symptoms and urinary retention of patients with large BPE. TUVP offers low levels of perioperative bleeding and short catheterization times with short hospital stay. Hence, there are potential financial and health benefits for patients and institutions.