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Keywords:

  • laser surgery;
  • prostate cancer;
  • radical prostatectomy;
  • laparoscopic surgery

Abstract

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. CONFLICT OF INTEREST
  8. REFERENCES

OBJECTIVE

To examine, in a pilot study, the feasibility of laser dissection of the neurovascular bundle (NVB) during nerve-sparing laparoscopic radical prostatectomy (NSLRP). NSLRP demands precise NVB mobilization with minimal collateral tissue trauma and optimal haemostasis. Unlike other methods of delivering energy, lasers have the potential to provide rapid, precise dissection with good haemostasis and minimal adjacent tissue injury.

PATIENTS AND METHODS

Five patients were treated with NSLRP; in patient 1 the right NVB was dissected using clips and scissors and the left NVB using the 1064 nm Nd:YAG laser (8 W, continuous-wave mode). In the subsequent four patients, the NVB was dissected bilaterally using the laser. The NVBs were excised for histological analysis.

RESULTS

In patient 1, the estimated blood loss for the left (laser) NVB dissection was 20 mL, while the estimated blood loss for the right NVB was 100 mL. The maximum depth of laser necrosis was 327 µm. For the next four patients the mean (range) total operative duration was 214 (166–245) min, the mean NVB dissection time 22 (8–33) min, the mean total blood loss 213 (100–300) mL, the mean estimated NVB blood loss 28 (10–45) mL and the mean depth of tissue injury was 687 µm. There were no complications. There was no recurrence, as assessed by prostate-specific antigen levels, at a mean follow-up of 12 months and all patients were continent.

CONCLUSION

Laser NSLRP was relatively straightforward and caused minimal blood loss, allowed a rapid dissection and minimal adjacent tissue injury. It is a promising technique that warrants further evaluation.


Abbreviations
NVB

neurovascular bundle

NSLRP

nerve-sparing laparoscopic radical prostatectomy

EBL

estimated blood loss.

INTRODUCTION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. CONFLICT OF INTEREST
  8. REFERENCES

Nerve-sparing laparoscopic radical prostatectomy (NSLRP) demands accurate and precise mobilization of the prostate from the neurovascular bundles (NVBs); however, the haemostatic energy sources, such as diathermy and ultrasonic shears, currently used by many might adversely affect cavernosal nerve function [1]. Laser energy differs from other energy sources in that it potentially provides rapid and precise dissection with minimal adjacent tissue injury, while securing effective haemostasis.

The principal laser types used laparoscopically are those based on CO2, KTP, Ho:YAG and Nd:YAG. CO2 lasers have a shallow depth of penetration but the currently used rigid delivery systems preclude fine laparoscopic dissection. The 532 nm KTP laser has good haemostatic properties combined with a shallow depth of penetration [2]. However, its green light emission necessitates the use of a filter to prevent interference with the camera system, and tinted safety glasses must be worn, both of which significantly detract from the laparoscopic view. The 2100 nm Ho:YAG laser does not require a filter and the safety goggles are clear. However, higher power settings are generally required and its photomechanical properties result in explosive effects on tissues, producing irregular cut margins and greater thermal tissue injury [2]. The 1064 nm Nd:YAG laser does not require a filter system and achieves good dissection and haemostasis with less photomechanical effects than the Ho:YAG laser, and was therefore selected for this analysis [2].

We hypothesised that Nd:YAG laser dissection of the NVBs during NSLRP might afford more precise dissection with better haemostasis and better nerve preservation than with current techniques. In the present pilot series we aimed to assess whether laser dissection of the NVBs is technically feasible. To our knowledge, this is the first study to examine the application of laser energy in NSLRP.

PATIENTS AND METHODS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. CONFLICT OF INTEREST
  8. REFERENCES

The feasibility of laser NSLRP was examined between September 2004 and January 2005 in five patients with clinically localized adenocarcinoma of the prostate. All patients had a PSA level of ≤ 15 ng/mL, a Gleason sum of ≤ 7 and clinical stage T1c. All patients either had pre-existing erectile dysfunction or preoperative variables (primary Gleason 4, PSA level >10 ng/mL) that precluded a definitive nerve-sparing procedure in accordance with our standard practice. This allowed the NVBs to be excised at the completion of each case for histological analysis. The primary endpoints assessed were the practicality of dissection, total operative duration, NVB dissection time (time taken, after dividing the lateral pedicles, to mobilize the NVBs to the prostatic apex), total estimated blood loss (EBL), EBL during NVB dissection, complications and depth of laser-induced necrosis (Table 1).

Table 1.  Results (mean values calculated for patients 2–5)
VariablePatientMean (patients 2–5)
12345
  • *

    Operative time excluding time taken to excise the NVBs and lymphadenectomy time. CR, control right; LL, laser left; NR, not recorded.

Total operative duration, min225 229 166 216 245 214
NVB dissection time, minCR NVB 5 LL NVB, 31   8  24  33  22  22
Total laser time, min12.58   5.97  12.38  15.55   6.05   8.63
Total energy, J593228645951747136394981
Adjusted NSLRP time, min*NR 217 132 162 197 177
EBL total, mL300 200 100 300 250 213
Estimated EBL for NVB, mLCR NVB, 100 LL NVB, 20  20  10  45  35  28
Hospitalization, nights2   2   2   3   3   2.5
Maximum depth of laser necrosis, µmleft NVB 327 8401400 182 326 687
Surgical marginsNegApex +NegApex +Neg

We previously evaluated the 532 nm KTP laser but found that the technical issues relating to the intraoperative laparoscopic view precluded any further evaluation of this laser type. Therefore in patient 1, to determine if Nd:YAG laser NVB dissection was practical, the right NVB was dissected using our standard technique of a combination of titanium clips and scissors, while the left NVB was dissected using the Nd:YAG laser.

NVB dissection times and blood loss from each NVB were compared and the depth of laser-induced necrosis was assessed. As the laser dissection compared favourably to our standard technique, we proceeded with a further four procedures using the Nd:YAG laser bilaterally.

An extraperitoneal, five-port, open access, antegrade laparoscopic approach was used, as we previously described [3]. The lateral pedicle was initially divided using a combination of titanium clips and sharp scissors dissection, stopping just short of the commencement of the NVBs, thus leaving a small amount of lateral pedicle tissue. The lateral prostatic fascia was then incised. The remaining right lateral pedicle and the right NVB in patient 1 was then mobilized using titanium clips and scissors. The 1064 nm Nd:YAG laser (Laserscope, San Jose, CA, USA) was used to divide the remaining left lateral pedicle and mobilize the left NVB in patient 1 and both NVBs in the subsequent four patients (Fig. 1).

image

Figure 1. Mobilization of the left NVB from the prostate using a 1064-nm Nd:YAG laser applied in the continuous-wave mode at 10 W.

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The NVBs were dissected as far distally towards the prostatic apex as possible, using a combination of laser energy and blunt dissection. The laser was used primarily to divide the tissue, but in areas where the NVB separated readily from the prostate, the hand-held instrument was used to bluntly dissect the NVB from the prostate. Irrigation was not used to simultaneously cool the area of dissection. Separate suction devices were used to estimate blood loss during NVB dissection on each side. The dorsal venous complex and urethra were then divided with scissors and, if required, any residual attached NVB was freed using the laser, and this additional NVB dissection time recorded. After the prostate was freed, each NVB was excised with scissors. To avoid confounding the histological analysis, diathermy was not used. The NVBs and prostate were placed into separate 10-mm laparoscopic organ-retrieval bags and removed. If required, the bladder neck was reconstructed before the urethrovesical anastomosis with interrupted 3/0 polylactic/polyglycolic acid copolymer suture. Wound closure and postoperative care proceeded as described previously [3].

In patients 1–4 a 300-µm fibre was passed down a Surgiwand II (Auto Suture, Norwalk, CO, USA) suction device. However, to improve stability of the tip of the laser fibre, in patient 5 a 600-µm fibre was passed through a 4.8 F Stamey open-ended ureteric catheter, both of which were then passed down a laparoscopic cholangiogram clamp (Fig. 2). The fibre, protected by the ureteric catheter from breakage by the metallic clamp jaws, was then secured into position. Using low power settings in the pulsed rather than continuous-wave mode might minimize the depth of tissue penetration. Therefore, in patient 1 dissection was commenced in the pulsed mode with the fibre applied as near-contact to the tissues at an 8-W power setting. However, as dissection proceeded too slowly this was changed to the continuous-wave mode applied in direct tissue contact. This mode of delivery resulted in faster dissection and was used in patients 1–4. A 10-W power setting was required in patient 5 because the larger 600 µm fibre decreases the applied power density and therefore a higher power setting is required to achieve the same speed of dissection.

image

Figure 2. Equipment used for laser dissection: (A) Suction cannula containing 300 µm laser fibre. (Insert A) Detailed view of cannula tip and laser fibre tip. (B) Cholangiogram clamp securing 600 µm laser fibre within 4.8 F Stamey open-ended ureteric catheter. (Insert B) Detailed view of cholangiogram clamp tip showing the laser fibre protected by the ureteric catheter secured by clamp jaws.

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The surgical samples were assessed histologically by one uropathologist experienced in examining radical prostatectomy specimens. The prostate and NVB specimens were embedded in paraffin wax, sectioned, and stained with haematoxylin and eosin. The NVBs were assessed at several locations to determine the maximum depth of laser-induced necrosis and the presence of underlying neural and vascular injury. The prostate margin status and Gleason grade were also recorded. Additional staining techniques to assess traditional histological changes of nerve injury were not used, as the nerve fibres are small and unmyelinated, and such further histological assessment is not indicative of nerve function [1]. Furthermore, the depth of coagulative necrosis correlates with the degree of thermal injury [4].

RESULTS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. CONFLICT OF INTEREST
  8. REFERENCES

The mean (range) patient age was 66  (61–69) years, the mean PSA level was 9.2 (6.0–12.6) ng/mL and the mean biopsy Gleason score was 6. All patients had clinical stage T1c disease. The mean weight was 76 (69–94) kg. In patient 1, the total operative duration was 225 min and total blood loss was 300 mL. The dissection time for the right NVB was 5 min, with an EBL (during right NVB dissection) of 100 mL. The dissection time for the left NVB was 31 min, with a laser activation time of 12.51 min and total laser energy of 5932 J. The EBL during left NVB dissection was ≈ 20 mL. Histological analysis of the left NVB showed a depth of laser injury of 327 µm with preservation of the underlying neurovascular architecture (Fig. 3). There were no complications, hospitalization was 2 nights and at 15 months of follow-up his PSA level was undetectable and he is continent (no pads/day).

image

Figure 3. Patient 1, left NVB tissue (haematoxylin and eosin, × 40) showing the zone of necrosis (327 µm) with preservation of the underlying neurovascular structures.

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Because patients 2–5 had bilateral laser NVB dissection their results are presented collectively. The mean total operative duration for these patients was 214 (166–245) min, but this time included a mean of 21 min to excise and remove the NVB for histological assessment, and a mean of 24 min for lymphadenectomy in patients 3–5, as patients eligible for NSLRP typically do not require a staging lymphadenectomy in our standard practice. When these times are removed the mean NSLRP time was 177 (132–217) min. The mean NVB dissection time was 22  (8–33) min, mean total laser time 8.63  (5.97–15.55) min and mean total energy usage 4981 (2864–7471) J. The mean EBL was 213 (100–300) mL and mean EBL during NVB dissection was 28 (10–45) mL.

The histological assessment of these four patients showed a mean prostate weight of 38 (32–44) g. The mean of the maximum depths of laser-induced necrosis of the NVBs for these four patients was 687  (182–1400) µm; the mean of the maximum depths of necrosis for all five patients was 623.6 µm. Two patients had positive apical margins but their PSA levels remained undetectable at 11 and 12 months of follow-up. There were no positive postero-lateral margins in any case. All patients had pT2 disease. The final Gleason score was 8 in patient 3, and 6 in the others. There was no tumour in the lymph nodes excised from patients 3–5. None of the patients was transfused and there were no complications. The mean hospitalization was 2.5 nights. At a mean of 11.5 months of follow-up all have undetectable PSA values and all are continent (no pads/day).

DISCUSSION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. CONFLICT OF INTEREST
  8. REFERENCES

NSLRP requires precise and accurate mobilization of the NVBs with effective haemostasis, a minimum of tissue handling and minimal injury to the periprostatic tissue containing the cavernosal nerves. However, currently used methods of haemostasis in LRP can affect cavernosal nerve function [1]. Diathermy and ultrasonic shears decrease the erectile response to cavernosal nerve stimulation [1]. Laparoscopic clips are much larger than the periprostatic vessels and can dislodge as dissection and tissue manipulation proceed. Consequently, to secure haemostasis, the clips need to be re-applied or alternatively the vessels can be over-sewn or treated with diathermy. However, such manoeuvres increase the handling of and potential injury to the NVBs, and might thus affect cavernosal nerve function and recovery. Clips placed on the NVBs can also traumatise the nerves. By contrast, laser energy potentially offers precise and accurate dissection with effective haemostasis and minimal injury to the NVBs.

The practicality of laser dissection was initially assessed in the first patient. The longer operative duration for the left NVB dissection (31 min) than the right (5 min) was related to our unfamiliarity with the laser technique. However, this patient had minimal blood loss during laser dissection, of ≈ 20 mL, and a minimal degree of adjacent tissue injury, with a depth of laser-induced necrosis of 327 µm and preservation of the underlying neurovascular architecture. We therefore proceeded with four further cases.

In these four patients (2–5) the mean operative duration was 214 min, but the mean time adjusting for lymphadenectomy and NVB excision was 177 (132–217) min, which compares favourably to our standard nerve-sparing mean operative duration of 188 min (unpublished data). NVB dissection was rapid, with a mean NVB dissection time of 22 min and a mean laser activation time of 8.6 min. The mean EBL was 213 mL, which compares favourably to our standard nerve-sparing mean EBL of 292 mL (unpublished data).

Laser dissection was relatively straightforward, and as our experience increased so too did the speed of dissection. As there was no requirement for a camera-filter system the operative view was not compromised, which contrasts with our previous experience with the KTP laser. Haemostasis was effective and secondary manoeuvres to control NVB bleeding, such as the application of clips or diathermy, or the over-sewing of bleeding points, were largely not required. We found that the occasional larger vessel of >2–3 mm, such as those found in the remaining lateral pedicle tissue, were difficult to control with the laser, and in two of the five patients additional clips were required to secure haemostasis.

Adjacent tissue injury was minimal, with a mean of the maximum depth of injury for all five patients of 615 µm. The depth of necrosis was variable and did not directly relate to either total laser time or energy. The effect of the Nd:YAG laser on tissue relates to the applied power density, which is influenced by the angle of incidence of the laser beam, the distance of the fibre tip from the tissue and the duration of exposure. In the first four patients, the laser fibre was passed down a suction cannula device and the unsecured fibre tip tended to ‘whip’ across the tissue with the laser beam applied tangentially. Therefore, the duration of activation and total energy generated by the laser source might not necessarily correlate with the actual laser dose delivered directly to the tissue. In addition, tissue folding, displacement and tangential sectioning during pathological processing can also affect the estimate of the depth of necrosis. In particular, the measurement of 1400 µm is by comparison disproportionately deep and could represent either an area of tissue at which the laser was particularly focused, or a pathological processing artefact.

The depth of laser injury compares favourably to that induced by ultrasonic shears and bipolar or monopolar diathermy which injure tissues across distances of ≈ 0.9 cm, 1.3 cm and 2.1 cm, respectively, depending on the tissue type and duration of activation [4]. Furthermore, evidence of injury related to monopolar diathermy can be evident several centimetres from the site of instrument activation [4]. The tips of the activated blades of the ultrasonic shears can reach temperatures of up to 150° C, whilst diathermy devices reach temperatures of >300° C [5]. Temperatures of >60° C, at which protein denaturation begins to occur, spread laterally over 1 and 2.2 cm for ultrasonic shears and diathermy, respectively [5]. In addition, the heat retained in the tip of these instruments after their activation can produce additional tissue damage should they be used for blunt dissection immediately after their use.

Bipolar diathermy forceps typically have an active cautery area of 12 × 5 mm, while the active blade of ultrasonic shears is 15 × 1 mm with a backstop of 15 × 3 mm. By comparison, the Nd:YAG laser fibre had a diameter of only 300 or 600 µm, which is much finer than the working surfaces of either the bipolar forceps or the ultrasonic shears. The combination of a shallow depth of laser injury, with the small diameter of the laser fibres, potentially allows for extremely fine and accurate dissection with a minimum of collateral tissue damage, particularly for the cavernosal nerves.

There were no complications during or after surgery, and the length of stay was similar to that of patients after our standard NSLRP, at 2–3 nights. No patient had positive postero-lateral margins, and PSA values remained undetectable. While two patients had positive margins present at the apical shave, it is unlikely that this was a result of laser dissection, as scissors were used to divide the urethra and mobilize the adjacent apex. While the Nd:YAG laser was used to mobilize any attached residual bundle near to the apex, there was no pathological evidence of laser use near the positive margins. There was no cancer in the resected NVBs. Any firm interpretation of oncological results is limited by the few patients in the series and the short follow-up. All five patients are pad-free.

This series evaluated the technical feasibility of laser dissection and the depth of laser injury during NVB mobilization during NSLRP. As the NVBs were excised erectile functional data could not be assessed, which is a limitation of the study. While intraoperative cavernosal nerve stimulation could be used as a surrogate endpoint for potency, the positive predictive value of this tool is low and most patients had pre-existing erectile dysfunction [6]. The depth of tissue injury might have been underestimated in the present study. The NVBs were assessed acutely and temporal changes of injury were not evaluated. In addition, ultrastructural features were not assessed and sublethal thermal injury could spread beyond the zone of necrosis. Ultimately, a functional assessment of the NVBs will provide the most meaningful evaluation of cavernosal nerve injury. As with any pilot series, the few patients and the short follow-up are limitations, and firm conclusions about the efficacy of laser dissection cannot be made. Further evaluation is required to confirm these data and to examine the effects of laser dissection on cavernosal nerve function.

In conclusion, this study is the first to report the use of laser energy to dissect the NVBs during NSLRP. Laser dissection of the NVBs using the 1064 nm Nd:YAG laser at a setting of 8–10 W in the continuous-wave mode is rapid, with good haemostasis and minimal adjacent tissue injury. This preliminary study suggests that Nd:YAG laser NSLRP is a feasible technique that warrants further assessment.

REFERENCES

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. CONFLICT OF INTEREST
  8. REFERENCES