Advances in nerve sparing for radical prostatectomy

Abstract

E impotence has been recognized as a sequela of radical prostatectomy since the operation was first reported. After Walsh and Donker described the anatomic course of the neurovascular bundle containing the cavernous nerve,1 and Walsh defined the anatomic radical prostatectomy,2 potency preservation has been sought after by urologists and patients. Initial reports by Walsh of potency rates as high as 80% contributed to a rekindling of interest in the operation. Coincidentally, a sharp rise in the detection of localized prostate cancer because of the advent of prostate-specific antigen (PSA) screening afforded unprecedented numbers of patients for whom prostatectomy was a treatment option. The nerve-sparing prostatectomy is now offered routinely to patients with localized prostate cancer throughout North America. However, major doubts remain about the efficacy of the nerve-sparing approach in most urologists’ hands. Despite the adoption of Walsh’s surgical modifications,3 a number of studies have found considerably lower rates of potency preservation than he reported. The American Urological Association Treatment Guidelines for localized prostate cancer reviewed the published reports before 1995 and found a rate of potency preservation between 15% and 80%.4 A meta-analysis of treatment outcomes in prostate cancer by Wasson et al.5 reported the probability of retaining erectile function after surgery to be 15%. This analysis was performed on studies published between 1966 and 1991. However, it included many studies performed before the nervesparing era and no studies published after 1991. Furthermore, many of the reports included patients who had sexual dysfunction before surgery. A more recent attempt to model the effect of treatment6 on erectile function on the basis of data from published reports derived a probability of maintaining normal erectile function after prostatectomy of 42% (95% confidence interval 40% to 43.3%). This calculation was based on studies up to 1995, with 15 additional studies carried out since the earlier meta-analysis and 14 studies specifically using a nerve-sparing prostatectomy. In short, there is room for improvement in the outcome of nerve-sparing prostatectomy with respect to recovery of potency. Injury to the neurovascular bundles may occur at three critical points: during urethral dissection, when the neurovascular bundle may be transected with the urethra; along the base of the prostate during division of the lateral pedicles; or during dissection of the seminal vesicles. Identification of the neurovascular bundles by anatomic landmarks may be obscured by bleeding, overlying tissue, surrounding fat, or blood vessels. Numerous issues cloud the precise analysis of erectile function after prostatectomy. Controversy exists regarding mechanisms responsible for erectile failure. Both vascular impairment and alterations in hormone levels after surgery have been implicated, in addition to neurogenic causes. Apoptosis has been reported to be induced by division of the cavernous nerves,7 supporting a multifactorial etiology for erectile failure after prostatectomy. The definition of erectile function is imprecise. Many studies report degrees of erectile function (ie, partial, full), which makes interpretation difficult. For example, erection is often defined by the ability to have intercourse. With an adequate supply of willingness, lubrication, and pushing, intercourse can be achieved with virtually no tumescence. Whether this patient is potent may be in the eye of the beholder. Thus, this apparently “hard” outcome measure lacks reliability and suffers from between-observer variability. The degree of erectile function preoperatively is L. Klotz has in the past received funding from Uromed Corporation for research projects. From the Division of Urology, Sunnybrook and Women’s Health Science Center, University of Toronto, Toronto, Ontario, Canada Reprint requests: Laurence Klotz, M.D., Division of Urology, Sunnybrook and Women’s Health Science Center, University of Toronto, 2075 Bayview Avenue, MG-408, Toronto, Ontario M4N 3M5, Canada Submitted: June 2, 1999, accepted (with revisions): July 22, 1999 UPDATE