prostate cancer ( pca ) is the fastest growing cancer in korea . according to the statistical data of the national cancer information center , the incidence of pca , 8.5 per 100,000 population in 1999 ,
the annual growth rate , 13.5% , is the fastest of all cancers in korea .
radical prostatectomy ( rp ) is the standard treatment for patients with clinically localized pca ( ct1-t2 ) and is associated with a life expectancy of > 10 years .
whereas open radical retropubic prostatectomy ( orp ) has been considered the gold standard for surgical treatment , minimally invasive procedures have been introduced with the intention of minimizing peri- and postoperative morbidities . despite the widespread use of robot - assisted laparoscopic prostatectomy ( ralp ) over the past decade , there are ongoing debates regarding the benefits of ralp compared with orp .
oncological controls in comparative studies have shown that ralp yields results similar to those of orp .
one recent study suggested that ralp results in no significant improvement in urological complications such as incontinence and erectile dysfunction .
however , not many studies have undertaken well - controlled , single - surgeon , direct comparisons of the outcomes of ralp and orp .
there have in fact been some reports on the impact of prostate volume on surgical outcomes . in orp
, a large - volume prostate is associated with longer operation time and increased complications .
patients with a small - volume prostate , meanwhile , have higher rates of biochemical recurrence ( bcr ) . in ralp , a small - volume prostate is correlated with early return of potency . however , there are few comparative reports on the impact of prostate volume on oncological and functional outcomes between the two types of surgery .
the aim of the present study was to investigate differences in oncological and functional outcomes according to prostate volume in patients with localized pca who underwent orp or ralp .
between september 2003 and april 2010 , 408 consecutive patients underwent single - surgeon rp for biopsy - confirmed pca at seoul national university hospital .
a total of 103 patients ( 25% ) underwent ralp and 305 patients ( 75% ) underwent orp .
preliminarily , after approval from our institutional review board , a total of 253 patients were included in this study .
we initially selected 176 consecutive orp and 77 ralp cases for clinically localized pca ( ct1-t2 ) .
the first 100 patients who had undergone orp and the first 25 to undergo ralp were excluded from the analysis owing to the learning curve .
postsurgery follow - up visits typically were scheduled at 3-month intervals for 1 year , and then semiannually for 1 year , and yearly thereafter .
patients within each surgical group were divided into two subgroups according to their prostate volume as measured by preoperative transrectal ultrasound : less than 40 g and 40 g or larger .
the oncological outcomes were assessed as positive surgical margin ( psm ) and 24 month bcr rates .
bcr was defined as two consecutive prostate - specific antigen ( psa ) measurements 0.2 ng / ml . the functional outcomes were assessed as continence and potency .
urinary continence was defined as the absence of any urinary leakage or the use of only one security pad .
potency was defined as spontaneous erectile function satisfactory for intercourse or with the use of phosphodiesterase-5 inhibitors on demand .
preoperative erectile function was assessed by use of a validated questionnaire , the international index of erectile function-5 ( iief-5 ) .
we evaluated postoperative potency in all patients who had been potent before surgery , defined as an iief-5 score of 12 , and who had undergone a bilateral or unilateral nerve - sparing procedure .
postoperative potency was determined at each follow - up by means of a detailed surgeon - conducted interview .
ralp was performed by the transperitoneal antegrade approach with the use of the da vinci robot system ( intuitive surgical inc . ,
the choice of surgical approach accorded with patient preference after discussion of the risks , benefits , and alternatives with the patient 's physician . in both groups ,
a uni- or bilateral nerve - sparing procedure was performed if clinically indicated by patient age , preoperative erectile function , and oncological parameters .
the baseline characteristics of the patients were summarized as the mean standard deviation for continuous variables and frequencies or as percentages for categorical variables .
the ralp and orp groups were compared by using the student 's t - test ( continuous factors ) and pearson chi - square test ( categorical factors ) .
kaplan - meier survival curves were compared across techniques by using the log - rank test for up to 24 months of follow - up . in all of the tests ,
a statistical analysis was performed with the spss ver . 13.0 ( spss inc . ,
the mean patient age was 67.06.76 years , and the median body mass index was 24.02.67 kg / m .
the mean preoperative psa level was 7.417.74 ng / ml . the mean preoperative transrectal ultrasound prostate volume was 4217.92 ml .
as for the patients ' clinical stages , 171 cases ( 68% ) were stage i and 82 cases ( 32% ) were stage ii .
the preoperative baseline clinicopathological demographics of the orp and ralp groups were comparable ( table 1 ) .
the mean operation time was significantly shorter in the orp group ( 151 minutes vs. 220 minutes , p<0.001 ) , whereas the mean estimated blood loss was significantly less in the ralp group ( 917 ml vs. 642 ml , p<0.001 ) .
the number of patients who had undergone a nerve - sparing procedure ( unilateral or bilateral ) was significantly higher in the ralp group ( 63% vs. 83% , p=0.004 ) .
the pathological stages were very similar in each group , with 53% of patients with organ - confined disease in the orp group compared with 54% in the ralp group .
however , there was a significant difference in the proportion of patients with a pathologic gleason score ; the proportion was more favorable in the ralp group ( p=0.008 ) .
the most common location of a psm in the two groups was at the apex .
psms were encountered less often with ralp than with orp , but without statistical significance ( 42% vs. 38% , p=0.394 ) .
the 2-year bcr - free survival rates were 88% ( 154 of 176 ) in orp and 94% ( 72 of 77 ) in ralp patients during the follow - up period .
a log - rank test showed no statistical difference between the two groups ( p=0.140 ) within 2 years of follow - up ( fig .
, urinary continence had been regained in 55% of patients at 1 month , 80% at 3 months , 92% at 6 months , 95% at 9 months , 96% at 12 months , and 98% at 24 months .
the corresponding ralp recovery rates were 38% , 71% , 84% , 88% , 94% , and 95% ( fig .
2 ) . after adjustment for age , operation type was not found to significantly affect postoperative urinary continence recovery ( p=0.058 ) .
of the 177 patients who underwent orp , 55 ( 31% ) were potent preoperatively , compared with 41 of the 77 patients ( 53% ) who underwent ralp .
in the orp group , nerve - sparing status was bilateral in 47 ( 85% ) and unilateral in 8 patients ( 15% ) ; the corresponding numbers in the ralp group were 33 ( 81% ) and 8 ( 19% ) , respectively . in the subset of potent patients , 28 of 55 ( 51% ) treated with orp and 23 of 41 ( 56% ) treated with ralp were potent at the 2-year follow - up .
the recovery rates after orp were 2% at 1 month , 6% at 3 months , 15% at 6 months , 22% at 9 months , 40% at 12 months , and 51% at 24 months ; after ralp , they were 0% , 17% , 29% , 29% , 54% , and 56% , respectively ( fig .
after adjustment for age and nerve - sparing status , the recovery of sexual function was comparable between the orp and ralp groups throughout the follow - up period ( p=0.418 ) . in the subgroup analysis for which patients were classified according to prostate volume into small ( < 40 g ) and large ( 40 g ) volume groups , in the orp small - volume subgroup ,
the potency rates were 0% at 1 month , 0% at 3 months , 10% at 6 months , 21% at 9 months , 35% at 12 months , and 55% at 24 months .
in the ralp small - volume subgroup , they were 0% , 24% , 36% , 36% , 56% , and 60% , respectively ( fig .
ralp was associated with quick potency recovery in the small - volume subgroup ( p=0.020 ) . between the two small - volume subgroups
, there was no significant difference in the time to continence or oncological outcomes . within the large - volume subgroups ,
patients who had undergone ralp were less likely to become continent than were those who had undergone orp ( p=0.048 ) .
in the orp large - volume subgroup , the continence rates were 57% at 1 month , 77% at 3 months , 91% at 6 months , 95% at 9 months , 95% at 12 months , and 97% at 24 months . in the ralp large - volume subgroup
, they were 31% , 56% , 75% , 81% , 88% , and 91% , respectively ( fig .
, there was no significant difference in the recovery of sexual function or oncological outcomes .
in the present study we compared the surgical , oncological , and functional outcomes of orp and ralp . whereas the study was not randomized , its main strengths were the single - center and single - surgeon setting ; the use of a validated questionnaire to evaluate preoperative erectile function , specifically , the iief-5 ; and the inclusion of consecutive patients . the same protocols for preoperative diagnosis and staging evaluation of pca , perioperative treatment , pathological evaluation , and surgical approaches were adopted for both study groups , and the follow - up periods were sufficiently long for evaluation of functional outcomes .
another strength of the methodology was the comparability of the baseline clinicopathologic characteristics between the two groups .
bcr and psm are the two commonly used indexes for assessment of oncological outcomes following rp . in the present study ,
the psm rates were similar in the two groups , and consistent with other , prior series .
the reported incidences of psm ranged from 11% to 37% after orp and from 9.6% to 26% after ralp .
although more nerve - sparing procedures were performed in the ralp group , the technique did not significantly increase the incidence of adverse outcomes .
the difference in the short - term bcr rates between the two groups was not statistically significant .
also reported similar bcr rates for ralp and orp groups at short follow - ups of 1 and 3 years , respectively .
sooriakumaran et al .   recently reported that biochemical - free survival after ralp was 84.8% at a median follow - up of 6.3 years .
long - term outcome data on psa progression are not yet available for ralp , owing to the relatively short history of their availability .
further follow - up is required to determine long - term oncological outcomes such as disease - specific death and overall survival . in the present study ,
the recovery of erectile function was more rapid in ralp patients with small - volume prostates .
we found a significant advantage of ralp over orp for those who had small - volume prostates at the 3- and 6-month follow - up , particularly for preoperatively potent patients ( iief-512 ) undergoing unilateral or bilateral neurovascular bundle sparing .
our postoperative potency rates were 24% after ralp and 0% after orp at the 3-month follow - up ( p=0.007 ) , and 36% and 10% at the 6-month ( p=0.026 ) , respectively . however , there was no difference in potency rates between the ralp and orp small - volume groups at 12 months ( 56% vs. 35% , p=0.095 ) or 24 months ( 60% vs. 55% , p=0.468 ) postoperatively .
neither was there any statistical difference in recovery of erectile function between the two large - volume groups .
tewari et al .   reported that patients after ralp had a more rapid return of erection : 50% at a mean follow - up of 180 days versus 440 days after orp .
rocco et al .   reported a significant ralp advantage over orp for patients , particularly younger patients , who had undergone a nerve - sparing procedure at 3 , 6 , and 12 months postoperatively .
however , krambeck et al .   reported no significant difference in potency rate at the 1-year follow - up .
this early return of erectile function could be attributed to preservation of potency with minimized damage to the neurovascular bundles , better magnified visualization , precise anatomical dissection , reduced blood loss , or improved anatomical - reconstruction ability by use of robotic assistance .
it has been postulated that in larger prostates , the neurovascular bundles are displaced posteriorly , where they are possibly obscured by the prostate , making them prone to injury .
also , a large prostate is less mobile in the pelvis , owing to the smaller available space .
these factors could offset the advantage of ralp for potency preservation . in the present findings
interestingly , patients with large - volume prostates seemed to recover continence more quickly after orp than after ralp .
found that 84% of patients were continent at the 12 month follow - up after ralp .
hu et al .   reported that men undergoing ralp were more likely to be diagnosed as incontinent .
malcolm et al .   found no difference in health - related quality - of - life " bother scores " related to incontinence .
reported no difference in continence after ralp or rrp at the 1-year follow - up .
others , meanwhile , have reported 12 month urinary continence rates as high as 97% after ralp .
our findings are interesting in light of the fact that ralp is thought to increase the precision of anastomosis and decrease the incidence of traumatic maneuvers on the urethrosphincteric complex .
we suspect that these outcomes are related to a combination of extensive apical dissection and overzealous diathermy at the bladder neck with over - tight suturing , though we have no direct evidence for this
. this difference might be attributable to the necessarily lengthy learning curve for making a running anastomosis compared with the interrupted anastomosis used for orp . or
, it might also be due to the differences between the retrograde and antegrade approaches .
in any case , there is no real explanation for such findings at the present time .
the main limitation of this study , a retrospective review of our database , was the lack of randomized allocation of patients into one of the two treatment arms .
the choice of surgical approach was based mainly on patient preferences and requests after they were fully informed about both procedures .
still , given that these groups were relatively well matched regarding the comparability of the patients ' baseline characteristics , the substantial differences in functional outcomes shown in the present results can be attributed mainly to the two different surgical approaches .
another concern is that because the patients underwent rp at a tertiary - care centre , the present study might not fully reflect epidemiological trends and , indeed , might have incorporated a certain degree of selection bias .
the other limitations of this study were the relatively small number of patients and the short follow - up period .
in this single - surgeon consecutive series , patients after ralp demonstrated early recovery of erectile function , especially those with small - volume prostates .
ralp was also associated with lower blood loss but slightly longer operation times when compared with orp .
a large - volume prostate was associated with lower rates of postoperative urinary continence recovery , particularly in ralp patients .
long - term follow - up and well - designed randomized controlled trials are required before definitive conclusions on oncological and functional outcomes between orp and ralp can be drawn .
 purposewe compared the impact of prostate volume on oncological and functional outcomes 2 years after robot - assisted laparoscopic prostatectomy ( ralp ) and open radical retropubic prostatectomy ( orp).materials and methodsbetween 2003 and 2010 , 253 consecutive patients who had undergone prostatectomy by a single surgeon were serially followed over 2 years postoperatively . 
 ralp was performed on 77 patients and orp on 176 . 
 the patients were divided into two subgroups according to prostate volume as measured by transrectal ultrasound : less than 40 g and 40 g or larger . 
 recoveries of potency and continence were checked serially by interview 1 , 3 , 6 , 9 , 12 , and 24 months postoperatively.resultsralp was associated with less blood loss ( orp vs. ralp : 910 ml vs. 640 ml , p<0.001 ) but a longer operation time ( 150 minutes vs. 220 minutes , p<0.001 ) than was orp . 
 no statistically significant differences were found between the two groups for oncological outcomes , such as positive surgical margin ( 40% vs. 39% , p=0.911 ) or biochemical recurrence ( 12% vs. 7% , p=0.155 ) . 
 the overall functional outcomes showed no statistically significant differences at 2 years of follow - up ( continence : 97% vs. 94% , p=0.103 ; potency : 51% vs. 56% , p=0.614 ) . in the results of an inter - subgroup analysis , 
 potency recovery was more rapid in patients who underwent ralp in a small - volume prostate than in those who underwent orp in a small - volume prostate ( 3 months : 24% vs. 0% , p=0.005 ; 6 months : 36% vs. 10% , p=0.024 ) . 
 however , patients who underwent ralp in a large - volume prostate were less likely to recover continence than were patients who underwent orp in a large - volume prostate ( 97% vs. 88% , p=0.025).conclusionspatients can be expected to recover erectile function more quickly after ralp than after orp , especially in cases of a small prostate volume . 
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
CONCLUSIONS