European Urology

Benign Prostatic Hyperplasia

Several procedures have become available for the minimally invasive treatment of lower urinary tract symptoms (LUTS) due to benign prostatic hyperplasia (BPH). Each has specific features and variable outcomes. Potassium titanyl phosphate (KTP) laser photoselective vaporization of the prostate (PVP) has gained attention as a promising treatment option for BPH because it offers an efficient and bloodless procedure [1] with a short learning curve. Its wide acceptance among practicing urologists has been widely recognized [2].

Data on the effect on sexual function in patients undergoing PVP have remained scarce, so the available evidence is low, despite the fact that to date, >350 000 PVP procedures have been performed worldwide. In recent years, only three prospective trials have analyzed the impact of PVP on erectile function (EF). Paick et al. [3] first reported a significant increase in International Index of Erectile Function (IIEF-5) score after surgery at 6-mo follow-up in a population with preoperative normal EF. Kavoussi et al. [4] and Hamann et al. [5] both reported no changes in EF after PVP at 12 mo. For all of these studies, the short follow-up represented a major limitation.

The long-term impact of PVP on EF in men with LUTS/BPH is addressed in the study by Bruyère et al. [6], appearing in the current issue of the Platinum Journal. With their findings, the authors are able to provide new elements for our knowledge on this interesting topic.

Their main finding is that EF is not compromised in the overall population, as IIEF-5 scores are comparable pre- and postoperatively. Nevertheless, the authors also emphasize that in patients with normal EF (IIEF-5 >19), postoperative scores were significantly decreased at 6 mo, 12 mo, and 24 mo.

At first glance, findings from this prospective trial might seem in line with what has been previously reported, although the reader must be cautious when interpreting them.

Compared to the study by Bruyère et al. [6], in which the highest energy level is used (4200 J/cm³ of prostate), patients in the study by Paick et al. [3] received PVP at lower energy levels and obtained the same results for efficacy of urinary symptoms with a lower incidence of erectile dysfunction at 6-mo follow-up. Similarly, Kavoussi et al. [4] and Hamann et al. [5] reported no worsening of EF after PVP at 12-mo follow-up but, again, used lower levels of laser energy. Notably in these two reports, preoperative sexual functional scores were significantly low, defining selected populations of patients with preoperative erectile dysfunction.

Large, prospective, controlled, randomized studies with long-term follow-up have not been reported so far for the PVP technique, so the level of current available evidence remains low. The study by Bruyère et al. [6] represents a reflection of real-life clinical practice. A major limitation of such studies is represented by the variation in patient characteristics. In fact, the study population included patients with or without catheter and with different baseline EF as well as patients who were treated with different laser generators. Real-life practice studies, however, usually have large enough sample sizes to allow subgroups analysis, but this is not the case in this study.

Although long-term data presented by Bruyère et al. [6] are interesting, this study raised some criticism because of the high attrition rate. At 2 yr, only 17 of the original 39 patients with preoperative normal EF (initial IIEF-5 >19) were evaluated. Firm conclusions on long-term follow-up can only be made when a more substantial percentage of patients are followed for >1 yr.

The reported finding that PVP might have a negative influence on EF in preoperatively potent patients warrants further, more accurate evaluation, possibly within the framework of a prospective randomized controlled study. Currently, we can only speculate about the pathophysiology of erectile dysfunction in potent men undergoing PVP. Theoretically, thermal damage of the periprostatic structures, such as neurovascular bundles (NVBs), is unlikely because of a relatively consistent penetration of <1 mm [7]. Because this is a disobstructive procedure providing a transurethral resection (TUR)–like cavity but not removing a large amount of prostatic adenomas, NVBs are further from the lumen after PVP than in a standard TUR of the prostate.

Experimental evidence is available on the dispersion of the laser energy in the residual prostate toward the capsule causing damage to the NVBs. Lee et al compared the histopathologic effect of 80- and 120-W lasers on canine prostates [8]. The 120-W high-performance system laser demonstrated a higher rate of vaporization; in particular, the depth of vaporization injury was associated either with a longer time of vaporization or with higher laser power applied. As more energy is applied and dispersed, more damage to the NVB is likely to occur. Bruyère et al. [6] did not find any difference between patients who underwent an 80-W procedure and patients treated with 120 W, but this comparison was performed in the overall population. Questions remain about the results obtained on patients treated with 80-W KTP and 120-W lithium triborate generators.

Hermanns et al have recently demonstrated that tissue damage could be also related to the energy dispersion caused by deterioration of the fibers [9]. They evaluated the relationship between loss of power and fiber deterioration after or during 80-W vaporization, demonstrating a median power drop of >80% compared with baseline after application of 275 kJ. A significant decrease of the median power output was found in 90% of the fibers during vaporization, leading to potential energy dispersion with severe damage of the tip (melting effect).

The energy used in this study from Bruyère et al. [6] is among the highest (255 ± 129 kJ), with a ratio of power to prostate volume of 4250 J/cm³. Unfortunately, the authors do not provide information on mean fiber numbers for patients used to generate such energy. This bias could have caused severe energy dispersion in the prostatic tissue. Improvements in the overall quality of the fibers are awaited to lower the reported deterioration and to minimize energy dispersion.

The concept of dispersion of energy causing erectile dysfunction and sclerosis of the prostate capsule is also based on a study from Horasanli et al. [10], in which postoperative storage symptoms and urge incontinence after laser treatment are reported up to 25.7% of subjects. In their experience, the high applied laser energy (247 ± 129 kJ) might have been beneficial with respect to hemostasis, but a significant number of patients probably had to pay a price in terms of postoperative urgency likely due to of the excessive dispersion of energy toward the prostatic capsule.

To reinforce this theory, it could have been of interest to evaluate the correlation of erectile dysfunction and postoperative storage symptoms and the rate of reintervention by including only preoperatively potent patients undergoing PVP. Currently available data do not provide enough evidence-based information to draw sound conclusions on this topic. We look forward to higher quality data to increase the current level of evidence.

Given the many shortcomings of this prospective analysis, a word of caution seems warranted, with a practical take-home message for the practicing clinician: A potential harmful effect of PVP on EF in potent patients should be considered when counseling on laser treatment for BPH. Long-term results from large-scale randomized trials at high-volume centers are eagerly awaited to definitively and properly assess the impact of KTP PVP on EF.