DISCUSSION
HoLEP procedure was first described by Gilling et al in 1998 and over the last two decades this technique became a valuable alternative in the management of large prostates due to the excellent functional outcomes, low perioperative morbidity as well as long-term durability of its efficiency.3Following its clinical introduction, the procedure has been performed by using a 100 W Ho:YAG laser device with energy levels of 2 J and frequency settings of 40–50 Hz for a long period of time.3, 21 In 2008 however, Rassweiller et al. published the first study regarding the efficacy and safety of a 50-W holmium laser device for HoLEP procedure.15 Although they were able to demonstrate the safe and effective application of the enucleation technique with this medium power device, majority of the practicing surgeons still tend to use more efficient high power HoLEP devices with this aim. With the false perception that MP devices are not effective and practical for tissue removal, high devices for HoLEP procedure are still being preferred. This approach also is forcing the industry to develop more powerful laser devices (exceeding 100W) which will bring higher cost issue together. Related with this issue again, since 2008, several studies have focused on the use of MP devices (50-80 W) with low energy settings in the effective and safe enucleation based removal of enlarged prostatic tissue which will clearly be more cost effective than the high power devices.14, 16, 18, 22In our present prospective comparative study, by using two different laser devices (50 W vs 100 W) the enucleation efficiency was found to be 1.14 g / min. where there was no statistically significant difference between Group 1 and Group 2 (1.15 vs. 1.11, p = 0.775). Similarly, in their original study Minagawa et al., performed HoLEP procedure with a 30 W power device and similar enucleation efficiency has been reported, although the average removed specimen weight was less than the values obtained in our study. Additionally they compared the outcomes on a surgeon’s experience based manner and enucleation time was shown to be significantly lower in HoLEP procedure when performed by experienced surgeon. Since the authors had no HP control group in the study, the results were compared with other HoLEP series performed with 100W power setting and the outcomes in terms of enucleation efficiency were acceptable as well as comparable compared with other reports using a HP laser.14 In another study, regarding the HoLEP procedure performed with 50 W device (2,2J- 18Hz) HoLEP by two experienced surgeons, the EE was again found to be similar to our findings. Again, the authors did not have include a control group and the obtained results were compared with the outcomes of previously performed HP HoLEP series where they found the EE values they found were higher than the results obtained by HP laser devices. They emphasized that the experience of the surgeon was an important factor ( rather than the power of the device used) to obtained such higher EE values.16 In the first randomized controlled trial comparing LP-HoLEP vs standard HP-HoLEP (50W and 100W energy settings), the authors reported no significant difference between 50W and 100W groups in terms of all operative parameters including the EE values.17 When we evaluate the outcomes of studies comparing different energy settings in the efficiency of enucleation during HoLEP procedure, it is noteworthy that EE has been reported to be lower in studies conducted prior to 2013 15, 23, 24compared to studies conducted in 2017 and thereafter. While mean EE values was ranging between 0.45-0.94 in previous studies, it has been found to range between 1.1-1.7 in recent studies.16, 17, 20 These findings in turn again emphasize well the importance of accumulated experience over the years by indicating that as surgeons acquire more experience the efficiency of the procedure increases as well independent from the power of the devices used. This has been also confirmed with our findings and we believe that depending on the experience of the surgeon the technique applied for enucleation is the key factor for an effective tissue removal regardless of the device power used. By using 25W vs 40W power settings, in their original study Rassweiller et al., reported an average hemoglobin decrease of 3.1 g / dl and a transfusion rate of 8% in their groups.15 Although these values were unexpectedly high, acceptable values have been reported in later studies involving patients treated with low and medium power settings. In their retrospective study including the data of more than two thousand patients, Becker et al. used the 100 W energy setting for HoLEP procedure and they reported an average hemoglobin decrease of 0.9 g/dl and a transfusion rate of 0.4%. 25 In another study comparing 50W and 100W energy settings, decrease in hemoglobin values were 0.9 g/dl and 0.7 g/dl, respectively.17 In our study, median hemoglobin decrease values were 1.3 g / dl in Group 1 patients, and 1.4 g / dl in Group 2 respectively. There was no statistical difference between the two groups on this aspect and, even the hemoglobin decrease was lower in Group 1 patients. Multiple regression analysis of our findings demonstrated that, the only independent variable in the prediction of hemoglobin decrease was the presence of biopsy anamnesis. We showed that hemoglobin decrease was higher in patients undergoing biopsy before HoLEP procedure. Regarding the possible underlying causes for the high likelihood of bleeding, acute or chronic inflammatory response may cause granulation in the tissue and these alterations could make it more difficult to separate the adenomatous tissue from the prostatic capsule during HoLEP. In addition to high risk of bleeding, difficulty in the separation of capsule may prolong the operation time and / or worsen of the surgical field visibility. Catheterization and hospitalization time were other important parameters correlating with laser settings used in HoLEP procedure. In our study, catheterization and hospitalization time were similar in the two groups. In a recent study performed by Becker et al., 40W energy setting was used for HoLEP procedure and catheterization, and hospitalization times were found to be similar to those in our study.16Lastly, evaluation of the functional outcomes during 3-months follow-up visit in our study showed a significant relief of obstructive symptoms in Group 1 patients with LUTS due to symptomatic BPH. Significant improvement observed in voiding parameters (Qmax, PVR) and validated questionnaires (IPSS, QoL) in Group 1 cases after 3 months following HoLEP procedure and these values were comparable with the results obtained in Group 2 cases. In summary, our study is the first study in the literature comparing the efficacy and safety of two different laser devices (MP vs HP) and we were able to show the efficient use of MP device in order to enucleate the large prostatic adenomas with excellent functional outcomes after 3- months. Our findings obtained with MP device were all comparable with the outcomes of HP devices. In the light of these observations we may claim that if the surgeon is experienced by applying his technique of enucleation in a successful as well as practicle manner, outcomes will be acceptable regardless of the power of the device used. This will in turn decrease the traditional huge demand for HP devices to perform HoLEP procedure with the false perception of “high power means higher efficiency” and as a result cost of the devices will be less by allowing the HoLEP procedure to be perfomed in a widespread manner in all parts of the world. Our study may have several limitations. Since our main purpose was to investigate EE and hemoglobin decrease, lack of the long-term functional results in these patients may be an important drawback. However as the first prospective study performed with this aim (by comparing two different power levels for HoLEP procedures performed by a single experienced surgeon) we believe that our well assessed functional outcomes during the postoperative 3 months into account may also contribute well to the existing information in the literature with reliable clinical implications. However we also believe that further studies with larger series of cases focusing on the role of power levels of the devices in HoLEP procedure are certainly needed. In conclusion, our current findings indicate well that HoLEP surgery can be performed in an effective and safe manner by using MP (50 W) devices. Surgeon’s experience is an important factor on this aspect and HoLEP devices with different maximum powers may provide similar efficiency and reliability. As a result, use of HP-HoLEP devices may lead to unnecessary equipment costs without changing the perioperative functional outcomes and complication rates. This will certainly limit the common application and acception of this valuable technique in all parts of the world due to higher costs.