Surgery Section - Sural Nerve Graft in Association with Radical Prostatectomy

IMPORTANT REMINDER

This Medical Policy has been developed through consideration of medical necessity, generally accepted standards of medical practice, and review of medical literature and government approval status.

Benefit determinations should be based in all cases on the applicable contract language. To the extent there are any conflicts between these guidelines and the contract language, the contract language will control.

The purpose of medical policy is to provide a guide to coverage. Medical Policy is not intended to dictate to providers how to practice medicine. Providers are expected to exercise their medical judgment in providing the most appropriate care.

Description
Erectile dysfunction is a common problem after radical prostatectomy. In particular, spontaneous erections are absent in patients whose extent of prostate cancer requires bilateral resection of the neurovascular bundles as part of the radical prostatectomy procedure. A variety of noninvasive treatments are available, including vacuum constriction devices and intracavernosal injection therapy. However, spontaneous erectile activity is clearly preferred by patients.

Recently, there has been interest in sural nerve grafting to replace cavernous nerves resected at the time of prostatectomy. The sural nerve is considered expendable and has been used extensively in other nerve grafting procedures, such as brachial plexus and peripheral nerve injuries. As applied to prostatectomy, a portion of the sural nerve is harvested from one leg and then anastomosed to the divided ends of the cavernous nerve. Studies report results from bilateral nerve grafts, as well as unilateral grafts when only one neurovascular bundle has been resected.  Reports are also being published  using other nerves, such as the genitofemoral nerve.

Policy/Criteria

Unilateral or bilateral nerve graft is considered investigational in patients who have undergone resection of one or both neurovascular bundles as part of a radical prostatectomy.

Scientific Background

Limited data are published regarding the long-term outcomes of sural nerve grafting; the largest study reported is a case series of 23 men with a mean 23 month follow-up. (2.) All men had clinically localized, but high volume prostate cancer such that bilateral resection of the neurovascular bundles was considered necessary. Prior to surgery all men reported spontaneous erection. Outcomes included assessment of erectile function based on: 1) the International Index of Erectile Function; 2) visual assessment; and 3) assessment by patient partners. Patients were also encouraged to use a variety of erectile dysfunction treatments, including intracavernosal injections, vacuum constriction devices, or sildenafil citrate, as needed. The results were compared to a group of 12 men who had undergone prostatectomy with bilateral nerve resection, but who declined nerve graft placement. Of the 23 men undergoing nerve graft, six (26%) had spontaneous medically unassisted erection sufficient for sexual intercourse. An additional six men (26%) reported 40% to 60% spontaneous erection that was insufficient for intercourse; four of these patients were able to have intercourse using sildenafil. Therefore, a total of ten of the 23 patients were able to have intercourse, either spontaneously or with pharmacologic therapy. A total of eleven men had no clinical response even with the use of sildenafil. Not unexpectedly, all outcomes were significantly better compared to the control group. Side effects of the sural nerve donor site, which included incisional pain and a sensory deficit along the lateral aspect of the foot, were considered tolerable. The authors noted improvement eight to twelve months postoperatively and accelerated improvement at twelve to eighteen months postoperatively. In addition, there are reports from the same group of surgeons who reported in 2001 that some 220 sural nerve grafts had been performed at their institution. (3) Some surgeons have performed unilateral sural nerve grafts. However, without a controlled study in this population, it is not possible to isolate the contribution of the sural nerve graft compared to the spontaneous recovery of erectile activity.

Singh and colleagues investigated whether unilateral sural nerve graft would improve urinary function after radical prostatectomy. (4) Patients with and without a sural nerve graft were invited to complete a questionnaire. At 12 months after surgery, 94.7% of patients with a sural nerve graft reported complete urinary control compared to 58.3% without a sural nerve graft. The authors concluded that these preliminary results required validation in larger, multicenter, prospective randomized studies.

Secin and colleagues reported results on 44 consecutive patients who underwent bilateral nerve grafting (5) The overall 5-year recovery of erectile function was 34% and the rate of consistent function was 11%. None of a number of variables (e.g., age, type of nerve [sural, genitofemoral, ilioinguinal], comorbidities) was significantly associated with recovery of postoperative erectile function. The authors concluded that nerve grafts might be beneficial in select patients but a randomized controlled trial was needed.

Sim reported on 2-year results in 41 patients who received unilateral sural nerve grafts following radical prostatectomy when one neurovascular bundle was resected. (6) In this series, recovery of erectile function was reported for 63% of patients (based on 24 of 38 patients). This study also reported on erectile function in another group of patients who had unilateral resection at the same institution but without a nerve graft. In this group that was older and was not matched on key characteristics to the group who received a nerve graft, the erectile function was 26.5% (13 of 49).

Nelson reported on results of using genitofemoral nerve grafts in 27 patients (5 with bilateral grafts) receiving radical prostatectomy. (7) At a mean follow-up of 14 months, 56% of patients reported erectile function sufficient for penetration. The authors noted uncertainty about whether their findings were a consequence of an effective unilateral nerve-sparing dissection or of the nerve grafting.

Zorn reported on sexual and neurologic function over a mean of 26 months in 27 patients receiving sural nerve grafts (23 unilateral, 4 bilateral). (8)  Several comparisons were made using their prospectively collected database of non-grafted patients.  At one year, continence rates were not different for the grafted versus non-grafted, but nerve-spared groups.  Sexual function was defined using validated questionnaires, and 24 of 27 nerve-grafted patients were potent preoperatively.  No difference between unilateral nerve graft and unilateral nerve-sparing with no grafting were noted with respect to return to baseline sexual function.  At a mean follow-up of 26 months, 47.8% of unilaterally grafted patients had regained potency, compared to 56% for age-matched unilateral nerve sparing with no grafting.

Namiki and colleagues published results from a 3-year study from Japan of unilateral sural nerve graft on recovery of sexual and urological function. (9)  A total of 113 patients were compared: 19 patients with unilateral nerve sparing plus sural nerve graft, 60 patients with unilateral nerve sparing but no grafting, and 34 patients with bilateral nerve sparing surgery.  Sexual function was assessed with validated questionnaires, and at two years, there was no difference between the nerve-grafted and the bilateral nerve-sparing patients with regard to sexual function scores.  At three years, 25% and 28% of patients in the nerve grafted and bilateral nerve-sparing groups, respectively, considered their sexual function as fair or good.  Urinary function returned to baseline in the nerve-grafted and bilateral nerve-sparing groups at 6 months and in the unilateral nerve-sparing group at 12 months.  Differences in sexual function were present at baseline with the nerve-grafted and bilateral nerve-sparing patients reporting higher baseline function than the unilateral nerve-sparing group.

While these numerous studies demonstrate that unilateral or bilateral nerve grafting is feasible, whether or not this technique results in improved patient outcomes following radical prostatectomy requires further study in randomized controlled trials. Randomized trials are needed to isolate the effects of treatment from spontaneous recovery and to remove selection biases present in the current studies.

References

1. BlueCross BlueShield Association Medical Policy Reference Manual, Policy No. 7.01.81
2. Kim ED, Nath R, Kadmon D et al. Bilateral nerve graft during radical retropubic prostatectomy: extended follow-up.  Urology  2001;58(6):983-7
3. Canto EI, Nath RK, Slawin KM. Cavermap-assisted sural nerve interposition graft during radical prostatectomy. Urol Clin North Am 2001;28(4):839-48
4. Singh H, Karakiewicz P, Shariat SF, et al.  Impact of unilateral interposition sural nerve grafting on recovery of urinary function after radical prostatectomy.  Urology  2004;64(6):1122-7
5. Secin FP, Koppie TM, Scardino PT et al.  Bilateral cavernous nerve interposition grafting during radical retropubic prostatectomy: Memorial Sloan-Kettering Cancer Center experience.  J Urol  2007;177(2):664-8
6. Sim HG, Kliot M, Lange PH et al.  Two-year outcome of unilateral sural nerve interposition graft after radical prostatectomy.  Urology  2006;68(6):1290-4
7. Nelson BA, Chang SS, Cookson MS et al.  Morbidity and efficacy of genitofemoral nerve grafts with radical retropubic prostatectomy.  Urology  2006;65(4):789-92
8. Zorn KC, Bernstein AJ, Gofrit ON et al.  Long-term functional and oncological outcomes of patients undergoing sural nerve interposition grafting during robot-assisted laparoscopic radical prostatectomy.  J Endourol  2008 Apr 17 [Epub ahead of print]
9. Namiki S, Saito S, Nakagawa H et al.  Impact of unilateral sural nerve graft on recovery of potency and continence following radical prostatectomy: 3-year longitudinal study.  J Urol  2007;178(1):212-6

Cross References
Erectile Dysfunction, TRG Medical Policy Manual, Surgery, Policy No. 25

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