Comparison of Surgical Stress in Patients Undergoing Open Versus Laparoscopic Radical Prostatectomy by Measuring Perioperative Serum Cytokine Levels

Abstract

Purpose:

We evaluated the perioperative serum levels of inflammatory cytokines in patients with prostate cancer (PCa) treated with open or laparoscopic radical prostatectomy (RP) and assessed the surgical stress based on the cytokine levels in addition to conventional clinical stress markers after surgery.

Patients and Methods:

One hundred sixty-five patients who received RP for clinically localized PCa were enrolled. Serum levels of interleukin (IL)-10, IL-6, tumor necrosis factor-α, IL-1β, IL-8, and IL-12p70 were quantitatively measured using a multiplex bead array at three time points (i.e., before the operation [pre-OP], immediately after the operation [post-OP], and on postoperative Day 1 [POD1]). The perioperative changes in serum stress markers, including cytokines, were compared between patients who underwent open and laparoscopic RP, and the predictors for high levels of postoperative cytokines were assessed.

Results:

The median age and estimated blood loss were significantly lower in the laparoscopic RP group than in the open RP group (P=.003 and P<.01, respectively). In all patients, body temperature, white blood cell count, and serum IL-10 and IL-6 levels were significantly higher at post-OP and POD1 than at pre-OP. Patients who underwent laparoscopic RP had significantly lower levels of serum IL-10, IL-6, and IL-1β at post-OP and POD1 than those who underwent open RP. Multivariate regression analyses showed that the surgical group (open versus laparoscopic) was an independent influencing factor on the levels of serum IL-6 and IL-10 at POD1 (P=.031 and P<.004, respectively) among various clinical perioperative parameters.

Conclusions:

Several inflammatory cytokines, particularly IL-6 and IL-10, are potential surgical stress markers in patients with PCa treated with RP. Based on cytokine production, our data support the view that laparoscopic RP is less invasive than open RP.

Introduction

Prostate cancer (PCa) is currently the most common malignancy in men and the second leading cause of cancer-related death in Western populations.¹ In Japan, morbidity and mortality due to PCa have been increasing. Radical prostatectomy (RP) is one of the standard treatments for localized PCa, and operative outcomes have been improving because of recent advances in surgical procedures.² To achieve a less invasive surgery, the laparoscopic technique is gaining popularity in the field of urology, including RP for localized PCa.^3,4 Accumulating evidence suggests that the outcome of laparoscopic RP (LRP) is comparable to that of open RP (ORP) despite less blood loss and an earlier recovery.⁵ However, an objective assessment of surgical stress response is difficult, and further investigation is needed to identify more precise markers to evaluate surgical stress.

Surgical trauma causes local activation of various cells, which release various cytokines and other mediators.⁶ Few studies have reported changes and differences in perioperative serum levels of acute response markers in patients with PCa who underwent RP.^3,7,8 Although measuring levels of humoral mediators such as inflammatory cytokines has the potential to be a predictive marker for surgical stress response, it is largely unknown how the levels of serum cytokines change during the perioperative period and which cytokine is the best marker for assessing surgical response in patients who undergo RP for PCa.

Here, we evaluated the perioperative serum levels of six inflammatory cytokines and well-known conventional stress markers such as body temperature (BT), white blood cell (WBC) count, and C-reactive protein (CRP) in patients with PCa treated with RP. We also compared ORP and LRP based on these markers and assessed candidate serum predictors of surgical stress after RP.

Subjects and Methods

Between April 2005 and December 2009, 165 patients who received RP for clinically localized PCa were included. All patients were treated at Akita University Hospital, Akita, Japan, and provided written informed consent to surgery and to use of their clinical data for this study. The selection of surgical approach was based on the surgeon's discretion and patient's request.

All patients who received ORP underwent the standard bilateral limited lymphadenectomy procedure reported by Walsh.⁹ LRP was performed using the transperitoneal approach in 2 patients and the retroperitoneal approach in 64 patients without pelvic lymphadenectomy. Clinical variables including age, body mass index, American Society of Anesthesiologists score, operation time, and estimated blood loss were also assessed.

Serum samples were obtained at three time points (i.e., before the operation [pre-OP], immediately after the operation [post-OP], and on postoperative Day 1 [POD1]). In each case, 4 mL of blood was drawn, and the serum was separated by centrifugation. The samples were aliquoted and stored at −80°C until assay. Six inflammatory cytokines (interleukin [IL]-10, IL-6, tumor necrosis factor [TNF]-α, IL-1β, IL-8, and IL-12p70) were quantitatively measured using the BD Cytometric Bead Array Human Inflammatory Cytokine Kit according to the manufacturer's instructions (BD Bioscience, Sparks, MD). In brief, the serum samples were incubated with a mixture of human inflammatory cytokine capture beads for 2 hours at room temperature. Samples and standards were processed using a FACSCalibur™ flow cytometer (BD Bioscience), and the data were analyzed using the CBA software program (BD Bioscience). The concentrations of the six cytokines were calculated using the standard curve method.

Data are reported as mean±standard error values and compared using the Mann–Whitney U test. A multivariate linear regression analysis was used for all variables to determine the potential significance of a host of factors on the levels of serum IL-6 and IL-10. Comparisons were considered statistically significant at P<.05.

Results

The characteristics and surgical outcomes of the patients who underwent ORP and LRP are summarized in Table 1. The mean age was significantly lower in the LRP group than in the ORP group (P=.003). The mean estimated blood loss was significantly lower in the LRP group than in the ORP group (P<.001). No significant difference was observed between the two groups for mean body mass index, American Society of Anesthesiologists score, or operation time.

Table 1.

Patient Characteristics and Surgical Outcomes

Characteristic	ORP (n=99)	LRP (n=66)	P value
Age (years)	67.4±0.6	64.8±0.6	.003
BMI (kg/m²)	24.3±0.3	24.0±0.4	.508
ASA score	1.3±0.5	1.2±0.5	.103
Operation time (minutes)	232.3±5.0	237.8±6.6	.497
Estimated blood loss (mL)	1274.5±88.8	491.4±40.2	<.001

Data are mean±standard error values.

ASA, American Society of Anesthesiologists; BMI, body mass index; LRP, laparoscopic radical prostatectomy; ORP, open radical prostatectomy.

We assessed the perioperative trends in the levels of clinical stress markers (BT, WBC, and CRP) and six inflammatory cytokines in all patients who underwent RP and compared the mean levels of the markers at post-OP or POD1 with those at pre-OP (Fig. 1). BT, WBC count, and the serum levels of IL-10, IL-6, IL-1β, and IL-8 were significantly higher at post-OP than at pre-OP (P=.002, P<.001, P<.001, P=.009, P<.001, and P<.001, respectively). BT, WBC count, and the serum levels of IL-10 and IL-6 continued to be significantly higher at POD1 than at pre-OP (P<.001). The mean levels of IL-1β and IL-8 decreased at POD1, and no differences in the levels of IL-1β and IL-8 were observed between pre-OP and POD1. No significant difference was observed in the CRP level between pre-OP and post-OP, whereas the CRP levels at POD1 were significantly higher than those at pre-OP (P<.001). No differences were observed for the perioperative levels of serum IL-12p70 or TNF-α. These results suggest that BT, WBC count, and the serum levels of IL-10 and IL-6 are surgical stress markers at post-OP and POD1. Serum IL-1β and IL-8 levels reflected surgical stress at post-OP but not at POD1. Serum CRP levels may increase at a later phase compared with other stress markers.

FIG. 1.

Perioperative changes in stress markers, including clinical factors and six inflammatory cytokines, in all patients treated by radical prostatectomy. *P<.05 compared with the preoperative (pre-OP) value. CRP, C-reactive protein; IL interleukin; POD1, postoperative Day 1; Post-OP, immediately postoperatively; TNF, tumor necrosis factor; WBC, white blood cell.

Table 2 shows the mean serum levels of the six inflammatory cytokines and the levels of BT, WBC, and CRP at pre-OP, post-OP, and POD1 according to the ORP and LRP groups. No differences were observed in any of the variables tested between the two groups for the pre-OP parameter levels. The only significant difference observed at post-OP was in the WBC count. The mean WBC count was significantly lower in the ORP group than in the LRP group (10,877±349.5 versus 11,993±391.7 cells/μL, P=.038). At POD1, BT, WBC count, and CRP were significantly lower in the LRP group than in the ORP group (P=.013, P<.01, and P=.008, respectively). Among the levels of six inflammatory cytokines, significant differences were observed in the levels of serum IL-10, IL-6, and IL-1β at POD1 between the two groups (P=.001, P=.006, and P=.046, respectively). The mean levels of these three cytokines were lower in the LRP group than in the ORP group (6.3±0.6 versus 4.2±0.4 pg/mL, 135.4±23.4 versus 68.0±4.8 pg/mL, and 3.8±1.0 versus 1.5±0.4 pg/mL, respectively). No differences in the levels of other cytokines were observed at POD1. The LRP group had significantly lower levels of several stress markers including inflammatory cytokines, and the differences in the stress markers appeared to be more evident at POD1 than at post-OP.

Table 2.

Changes in Inflammatory Markers

Marker, interval	ORP	LRP	P value
Body temperature (°C)
Pre-OP	36.3±0.0	36.2±0.05	.588
Post-OP	37.6±0.1	37.7±0.06	.530
POD1	37.4±0.1	37.1±0.07	.013
WBC count (cells/μL)
Pre-OP	5776.5±142.5	5368.2±138.9	.051
Post-OP	10,877.3±349.5	11,993.9±391.7	.038
POD1	10,519.4±262.1	8872.3±228.6	<.001
CRP (mg/L)
Pre-OP	0.2±0.1	0.1±0.0	.068
Post-OP	0.1±0.0	0.1±0.0	.202
POD1	6.6±0.3	5.4±0.3	.008
IL-12p70 (pg/mL)
Pre-OP	1.8±0.3	1.2±0.3	.220
Post-OP	1.6±0.3	1.1±0.3	.178
POD1	1.5±0.3	1.3±0.3	.609
TNF-α (pg/mL)
Pre-OP	18.6±3.9	9.9±2.9	.074
Post-OP	12.4±5.6	10.5±2.1	.795
POD1	25.2±10.0	8.2±2.2	.100
IL-10 (pg/mL)
Pre-OP	2.1±0.2	2.0±0.2	.665
Post-OP	7.0±1.1	5.3±0.8	.225
POD1	6.3±0.6	4.2±0.4	.001
IL-6 (pg/mL)
Pre-OP	43.7±19.4	58.4±49.1	.751
Post-OP	187.9±76.1	174.2±36.3	.889
POD1	135.4±23.4	68.0±4.8	.006
IL-1β (pg/mL)
Pre-OP	4.7±1.1	13.1±10.5	.323
Post-OP	42.8±22.3	30.6±16.2	.692
POD1	3.8±1.0	1.5±0.4	.046
IL-8 (pg/mL)
Pre-OP	412.0±108.5	204.7±94.9	.152
Post-OP	845.7±380.7	1583.4±557.2	.259
POD1	361.6±166.8	131.9±41.2	.588

Data are mean±standard error values.

CRP, C-reactive protein; IL, interleukin; LRP, laparoscopic radical prostatectomy; POD1, postoperative Day 1; Post-OP, immediately postoperative; Pre-OP, preoperative; ORP, open radical prostatectomy; TNF-α, tumor necrosis factor α; WBC, white blood cell.

Next, we evaluated the perioperative factors influencing the levels of IL-6 and IL-10 at POD1 (Tables 3 and 4, respectively). Multivariate regression analyses showed that surgical group (LRP versus ORP) was an independent influencing factor on the levels of serum IL-6 and IL-10 at POD1 (P=.031 and P=.004, respectively). Pre-OP serum IL-10 was also an independent influencing factor for the levels of serum IL-10 at POD1 (P<.001). These results indicate that the selection of surgical approach was a critical factor influencing the high inflammatory cytokine levels after RP.

Table 3.

Multivariate Analysis of Potential Influencing Factors on Levels of Interleukin-6 at Postoperative Day 1

Variable	Standardized coefficient	P value
Age (years)	0.033	.699
Body mass index (kg/m²)	−0.018	.825
ASA score	−0.031	.708
Open versus laparoscopic	−0.182	.031
Preoperative IL-6 (pg/mL)	0.002	.976
Operative duration	0.720	.444
Estimated blood loss	−0.380	.718

ASA, American Society of Anesthesiologists; BMI, body mass index; IL, interleukin.

Table 4.

Multivariate Analysis of Potential Influencing Factors on Levels of Interleukin-10 on Postoperative Day 1

Variable	Standardized coefficient	P value
Age (years)	0.038	.632
Body mass index (kg/m²)	0.052	.499
ASA score	−0.038	.615
Open versus laparoscopic	−0.225	.004
Preoperative IL-10 (pg/mL)	0.296	<.001
Operative duration	−0.005	.957
Estimated blood loss	−0.088	.365

ASA, American Society of Anesthesiologists; BMI, body mass index; IL, interleukin.

Discussion

We evaluated the perioperative changes in stress markers, including six inflammatory cytokines, in patients with PCa who underwent RP and found that several stress markers were altered significantly after RP. Additionally, LRP was suggested to be associated with significantly less tissue damage than ORP based on the surgical stress markers evaluated in this study. In the multivariate analysis, the selection of a laparoscopic approach was an independent predictor for low serum IL-6 and IL-10 levels at POD1 among the preoperative variables reported to be risk factors for a surgical stress response.

Cytokines, which are produced during and participate in inflammatory processes including surgical trauma, are the chief stimulators of the production of acute-phase proteins.¹⁰ These inflammation-associated cytokines include IL-6, IL-1β, TNF-α, IL-8, IL-10, and IL-12.^3,10–13 The pattern of production of specific cytokines is believed to vary and differ under different inflammatory conditions. In our study, serum IL-10, IL-6, IL-β, and IL-8 levels increased after RP. Serum IL-6 and IL-10 levels continued to be high even at POD1. In contrast, IL-1β and IL-8 levels peaked just after surgery and then immediately decreased, although we did not measure cytokine levels between post-OP and POD-1. A study that assessed perioperative levels of cytokines in patients with colorectal cancer showed that serum levels of IL-1β and IL-8 peaked at an early stage after surgery and then immediately decreased.^14,15 These results suggest that some markers, such as IL-1β and IL-8, are available to use as stress markers but only at the early period after surgery. IL-6 is the chief stimulator of the production of most acute-phase proteins¹⁶ and is useful for predicting complications and organ failure after surgery.^17,18 IL-10, an anti-inflammatory cytokine, is produced by monocytes and macrophages, T-helper 2 cells, and B lymphocytes,¹⁰ and an elevation in serum IL-10 level after surgery has been reported.¹⁹ Of the six inflammatory cytokines investigated in this study, IL-6 and IL-10 were relevant candidate stress markers for patients with PCa who underwent RP because these markers remained at high levels at least at post-OP and POD1. In our correlation analyses, postoperative serum levels of IL-6 and IL-10 were significantly associated with estimated blood loss, operative duration, postoperative BT, and postoperative serum levels of CRP, which are well-known surgical stress markers. It would be interesting to know whether the differences in the postoperative cytokine levels are associated with recurrence rate and long-term outcome after RP.

Several urological studies have investigated the immune response during surgery using serum cytokine levels,^3,8,7,20 and several studies support our finding that IL-6 and IL-10 are good candidate serum predictors or markers for surgical stress. Miyake et al.³ found that serum levels of Il-6, IL-10, and granulocyte elastase are useful as objective surgical stress markers and that laparoscopic surgery is considered markedly less stressful than open surgery based on cytokine production. Wang et al.²⁰ investigated surgical stress in patients with bladder cancer treated with radical cystectomy to measure serum levels of IL-6 and interferon-γ; they showed that serum IL-6 levels in the laparoscopic group were significantly lower than those in the open group during and after surgery. In contrast, Jurczok et al.⁸ reported a direct comparison between ORP and extraperitoneal LRP by measuring CRP, serum amyloid A, IL-6, and IL-10 before, during, and after surger; in contrast to the results in our study, they reported no differences in serum levels of these acute-phase markers between the two groups. Although we do not know the exact reason for these discrepancies, they may have been caused by differences in racial background, blood sample timing, operative method, postoperative protocol, mode of anesthesia, or patient age and gender. A recent study found that patients who underwent robotic RP have lower tissue trauma than those who underwent open surgery based on serum CRP and IL-6 levels.⁷ It is interesting to compare surgical responses between robotic and laparoscopic prostatectomy. Because elevated serum IL-6 is associated with PCa aggressiveness and a predictive marker for biochemical recurrence after prostatectomy,²¹ a preoperative evaluation of changes in serum IL-6 levels would be valuable not only for detecting surgical stress but also for predicting prognosis.

Some limitations affecting the current findings must be considered. First, the choice of surgical approach was based on the surgeon's discretion and patient's request. Second, the two groups had slight differences in background such as mean age and estimated blood loss. Additionally, the laparoscopic group included a slightly different kind of surgical procedure. Thus, the results may require validation by a standardized study such as a multicenter prospective trial.

In conclusion, several inflammatory cytokines, particularly IL-6 and IL-10, are potential surgical stress markers in patients treated with RP. Based on cytokine production, our data support the view that LRP is less invasive than ORP. The long-term oncological effect of the differential cytokine levels remains unknown.

Footnotes

Acknowledgments

We thank Yuka Izumida, Tomomi Kakizaki, and Yoko Mitobe for their excellent technical assistance.

Disclosure Statement

No competing financial interests exist.

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