Pelvic Lymphadenectomy

The pelvic lymph nodes are the initial site of spread of prostatic, bladder, and proximal urethral malignancies. Tumors of the penis, scrotum, and distal urethra spread primarily to the inguinal lymph nodes but can involve the pelvic lymph nodes. Testicular tumors rarely involve the pelvic lymph nodes unless there is massive retroperitoneal disease or a history of orchidopexy or prior pelvic procedures. Most urologists perform pelvic lymph node dissections in patients with prostate or bladder cancer.

DIAGNOSIS

Pelvic lymphadenectomy is performed as a staging procedure in patients with prostate or bladder cancer.

INDICATIONS FOR SURGERY

Presence of lymph node metastases from prostate cancer has prognostic significance and is a harbinger of disease progression.1 In a series from Memorial Sloan-Kettering Cancer Center, 86% of patients with pelvic lymph node metastases measuring over 3 cc had disease progression within 5 years. Pelvic lymph node dissection has not been shown to be of therapeutic benefit in the treatment of prostate cancer.4 However, there are patients who have small-volume nodal disease and prolonged survival after lymphadenectomy and radical prostatectomy. It is unclear whether this prolonged survival is a consequence of tumor biology, the treatment, or a combination of the two.

P>Pelvic lymph node dissection may be performed as a staging procedure before definitive radiation therapy, as a separate procedure for prostate cancer, i.e., before a radical perineal prostatectomy, or concomitant with a radical retropubic prostatectomy.

Serum PSA screening has led to a stage migration in newly diagnosed cases of prostate cancer and to a lower incidence of pelvic lymph node positivity. The incidence of unsuspected pelvic lymph node disease found at exploration has decreased. In the past, nearly 25% of patients with clinically localized prostate cancer were found to have lymph node metastases at the time of surgery.10 A review of the last 140 pelvic lymph node dissections performed at the University of California–Davis, for clinically localized prostate cancer revealed four cases of lymph node involvement.

We perform pelvic lymph node dissections concomitantly with a retropubic prostatectomy but feel that, with the lower incidence of nodal disease, performing them as a separate procedure, i.e., laparoscopically, is not cost-effective. For patients undergoing a perineal prostatectomy, there are a small number who would benefit from a lymphadenectomy. For patients being treated with radiation therapy, we no longer perform a lymph node dissection.

For bladder cancer, there is more agreement in favor of the benefits of pelvic lymphadenectomy. A series from Memorial Sloan-Kettering Cancer Center demonstrated that the 5-year survival rate for patients with pelvic lymph node metastases was 9%.3 This would suggest that the pelvic lymph node dissection is mainly of prognostic rather than therapeutic value. However, Skinner reported a 35% 3-year survival rate for patients who were found to have a limited number of positive lymph nodes at the time of surgery, suggesting that the node dissection may have therapeutic benefits. The presence of positive lymph nodes in bladder cancer patients has implications for treatment options. Some urologists would treat with chemotherapy and reevaluate the bladder rather than proceeding with the radical cystectomy, but others favor debulking the tumor with cystectomy followed by postoperative chemotherapy. If we find grossly enlarged lymph nodes with histologic evidence for metastatic disease, we follow the former course of therapy. However, if the lymph nodes are grossly normal, we proceed with the radical cystectomy without sending the lymph nodes for frozen section evaluation. A national study is under way assessing the value of neoadjuvant chemotherapy. If it reveals an advantage for preoperative chemotherapy, the finding of nodal disease at the time of surgery becomes more challenging. Some urologists might argue that, in this situation, surgery would be the only chance for the patient, but others would argue that, neoadjuvant chemotherapy having failed, surgery would have little role in the management of these patients.

ALTERNATIVE THERAPY

Noninvasive methods of detecting pelvic lymph node spread have not been reliable. Various radiologic tests, i.e., ultrasound, computerized tomography, magnetic resonance imaging, and pedal lymphangiography, have been used to detect pelvic lymph node disease, but these have had low sensitivity. As a marker for prostate cancer, the use of serum prostate acid phosphatase (PAP) has low sensitivity and specificity. In addition, the use of serum prostate-specific antigen (PSA) alone is not a good predictor of pathologic stage, as there can be significant overlap between the PSA and the pathologic stage. Pelvic lymph node dissection is the definitive means of evaluating lymph node status in patients undergoing extirpative procedures for urologic malignancy.

With the arrival of minimally invasive techniques, laparoscopic lymphadenectomy has been performed. Another modification is to perform the dissection through a minilaparotomy incision when it is done as a separate procedure. In comparing the efficacy, morbidity, and cost effectiveness of a minilaparotomy pelvic lymph node dissection to those of a laparoscopic or standard open pelvic lymphadenectomy, the minilaparotomy approach had a similar lymph node yield to the standard open procedure and a similar shortened hospital course to the laparoscopic dissection, but at a lower cost compared to the other two.8

Much has recently been written questioning the need for pelvic lymph node dissection before definitive treatment for prostate cancer. On preoperative evaluation, there may be patients with a low likelihood of lymph node disease who do not need a lymphadenectomy. This may not eliminate lymphadenectomies completely, but it could decrease the number performed. A similar change occurred with PSA values and bone scans for prostate cancer staging. Narayan et al. found an 11% overall incidence of positive pelvic lymph nodes.6 In patients with PSA values less than or equal to 10 and Gleason grades less than or equal to 6, fewer than 3% had lymph node metastases. They felt that, in this group of patients, a staging pelvic lymphadenectomy would not be necessary. Campbell et al. reported a lymph node positive rate of 6.5% in patients with clinically localized prostate cancer, whereas if at least one favorable characteristic (Gleason grade less than 6, PSA less than 10, or nonpalpable tumor) was present, only 2.2% had lymph node involvement. Patients with a low probability of lymph node involvement, i.e., low Gleason grade and low PSA, might not require a pelvic lymph node dissection, which adds both cost and time to the definitive treatment. However, this is still somewhat controversial.

DESCRIPTION OF PROCEDURE

Prostate Cancer

The boundaries of the traditional pelvic lymph node dissection were those used in combination with radical cystectomies for bladder malignancies. They included the pelvic sidewall laterally, the paravesical fascia and peritoneum medially, the genitofemoral nerve superiorly, the obturator nerve inferiorly, and the femoral canal distally. Proximally, the dissection was carried varying distances up the common iliac artery. Most urologists now feel that only the obturator nodal packet need be removed for three reasons:

First, the obturator nodes are involved in 87% of cases when lymphatic metastases are found.

Second, the procedure is for staging and not therapy, so a more extensive dissection is of little benefit.

Third, if radiation therapy is used for local control following surgery, patients who had an extensive lymphadenectomy have a higher incidence of scrotal or lower limb edema.

Preoperatively, pneumatic compression devices (PCDs) are placed, and patients are given subcutaneous heparin as prophylaxis against deep venous thrombosis. Supine or lithotomy position may be used, although we use the low lithotomy position. The sacrum is positioned over the table break or a roll to allow for hyperextension of and better vision into the pelvis. The bladder is emptied using a Foley catheter. A midline incision is made from below the umbilicus to the symphysis pubis down through the anterior rectus sheath. The posterior rectus sheath is incised for 2 to 3 cm above the linea semilunaris to aid in lateral retraction of the wound. An extraperitoneal lymph node dissection is usually performed. If the peritoneum is entered during this incision, the defect is closed with absorbable suture.

The transversalis fascia is sharply divided in the midline to allow lateral dissection superficial to the peritoneum. This helps to avoid injuring the inferior epigastric vessels. The iliac vessels are exposed by bluntly sweeping the peritoneum superomedially. The vas deferens are encountered during this maneuver and may be divided. The table is tilted toward the first side for evaluation. If the prostate cancer is confined to one lobe, the dissection is begun on that side. A self-retaining retractor is applied, with care taken not to injure the inferior epigastric vessels. We use the Buchwalter retractor without the post, as it can be more quickly applied and the post can interfere with the surgeon. Other self-retaining refractors may be used.

We place the Buchwalter retractor on top of sterile towels, one on each thigh and one on the abdomen. A bladder blade and moist lap sponge are used to retract the wound laterally on the side of the dissection. A malleable retractor and moist lap are placed on the bladder and used to retract the bladder toward the contralateral side. A third retractor is placed at the apex of the wound. With these three retractors, excellent visibility can be obtained.

The nodal packet is palpated to detect grossly enlarged lymph nodes. If such nodes are found, they are sent for frozen section evaluation following removal. If no enlarged nodes are palpated, we continue with the lymphadenectomy and prostatectomy and do not send the lymph nodes for frozen section.

The external iliac artery is identified, and dissection of the lymph node packet is begun over its anteromedial aspect. The correct plane of dissection is easily found here, and there are no other structures in this area to be damaged. The dissection is brought proximally to the bifurcation of the common iliac vessels and distally to the femoral canal. The lymph node of Cloquet is the most distal aspect of the dissection. Lymphatic channels into this node and surrounding the external iliac vein are carefully clipped and divided. We place a right-angle clamp around the lymph node packet and ligate it with a 2-0 silk tie. A large right-angle clip is placed below the tie. As the nodal packet is divided and swept superiorly, an accessory obturator vein may be found and should be ligated and divided to avoid avulsion. Identification of this vein is necessary, as damage can cause extensive bleeding.

With gentle lateral retraction of the external iliac vein, the lymph node packet is dissected off the pelvic sidewall laterally. Although a vein retractor is usually used for this maneuver, we use a peanut/Kittner dissector. Identification of the obturator nerve is essential as the dissection is carried into the pelvic fossa to avoid injuring it. The packet is freed from the obturator nerve and vessels. The obturator vessels are spared if they are in their usual location below the nerve. If they are above the nerve or involved with the lymph node packet, it is best to ligate and divide them before bleeding can occur. This is especially true near the femoral canal. The superior attachment of the packet is now near the internal iliac artery. We previously identified and dissected out the ureter, but, in most cases, we no longer do this. To ensure the ureter is not damaged by a clip, the specimen is split over the obturator nerve, and a right-angle clip is placed over either limb of the split packet on each side of the nerve so that the ureter cannot accidentally be included in the clip. Additional loose attachments to the proximal hypogastric vessels are clipped and divided. The entire packet is sent to pathology as the two portions divided over the obturator nerve. The obturator fossa is irrigated. It had been our routine to leave a gauze sponge in the fossa for hemostasis; however, we now do this only for minimal oozing. The same dissection is then performed on the contralateral side to complete the lymph node dissection. We place one or two Jackson–Pratt drains in the pelvis postoperatively.

Bladder Cancer

The dissection is similar to the one described above for prostate cancer with some differences. The incision is carried to just above the umbilicus and down to the pubic bone. We palpate the pelvic lymph nodes while remaining extraperitoneal. If no grossly enlarged nodes are felt, the dissection becomes intraperitoneal. The peritoneum is entered in midline, and inspection is performed of the intra-abdominal organs for signs of metastatic disease. If none are found, dissection is continued by mobilizing the cecum and ascending colon. The peritoneum is incised along the white line of Toldt, and the right hemicolon is rolled medially. The right ureter is identified and freed superiorly and inferiorly. Inferiorly, this leads to the bifurcation of the iliac vessels. In freeing the peritoneum, we routinely divide the vas deferens. On the left, the peritoneum is incised lateral to the sigmoid colon, and it is reflected medially. The left ureter is identified and freed as on the right. Mobilization is aided by dividing the vas deferens.

The self-retaining retractor may be placed as described above. The bowel can easily be retracted into the upper abdomen, as it has been mobilized. The node dissection begins over either common iliac artery just proximal to the bifurcation. It is carried down the hypogastric artery to the superior vesicle artery, which is identified and divided. The remainder of the lymph node dissection is similar to that for prostate cancer.

OUTCOMES

Complications

Although pelvic lymph node dissection is usually a relatively short procedure with little morbidity, it has a potential for significant complications. These can be divided into intra- and postoperative complications. Paul et al. reported an 8.6% incidence of intraoperative complications, an 8.7% immediate postoperative wound complication incidence, and an additional 31.4% immediate non-wound-related complication rate. They also reviewed the complication rates reported in multiple studies. These ranged from 4% to 53% with a mean rate of 26.6%. Intraoperative complications can be minimized by familiarity with the pelvic anatomy and careful dissection to identify vulnerable structures. The most common vascular injury is to the accessory obturator vein. Care should be taken not to avulse the obturator vessels as they enter the pelvic foramina, as they will retract caudally, and ligation will be difficult. If this occurs, bone wax can be used. Significant injuries to the external iliac vessels require repair, sometimes with the aid of a vascular surgeon. Transection or avulsion of the obturator nerve leads to difficulties with adduction of the ipsilateral leg and is usually irreparable. Splitting the nodal packet as described reduces the chance of inadvertent nerve injury.

Ureteral injuries are uncommon and require repair when encountered. A problem with ureteral injuries is that they are not always identified at the time of surgery. These are often the result of a clip inadvertently being placed across the ureter. Therefore, as we now dissect out the lymph node packet, we no longer specifically look for the ureter. However, we always place a clip on the upper end of the nodal packet after splitting it over the obturator nerve in a cranial-to-caudal direction to avoid injury to the ureter, identified or not. If there is any concern for ureteral injury, the ureter must be dissected out and fully visualized.

Postoperative complications include those related and unrelated to the wound. Wound infections are uncommon, especially when prophylactic antibiotics are given. Dehiscence is similarly uncommon. Seroma and hematoma formation are more common and may require drainage and local wound care.

Prolonged lymph drainage and lymphocele formation may occur in 3% to 12% of patients. Prolonged drainage is treated by instilling autologous blood or Betadine solution through the preexisting drains as sclerosing agents. If Jackson–Pratt or similar drains are used, tissue will eventually grow into the drains. This has occurred twice in our experience, and in both cases a general anesthetic was required for drain removal. We now remove all drains or treat them as described above for prolonged drainage at the end of 2 weeks. Although it has been reported that the use of subcutaneous heparin increases the incidence of prolonged lymph drainage, this has not been our experience. Our rate of prolonged lymph drainage and/or symptomatic lymphocele formation is under 3%. Symptomatic lymphoceles can often be successfully treated with percutaneous drainage under radiologic guidance. Although some lymphatic drainage is expected, careful dissection and meticulous ligation of lymphatic channels help minimize the risk of prolonged drainage.

Any patient with prolonged or excessive lymph drainage must be evaluated for a urinary leak. This may be done by sending a sample of the fluid for creatinine. If a urine leak is found, this may be from either the anastomosis or an unrecognized ureteral injury. If the latter is suspected, it should be immediately investigated.

Thrombophlebitis and deep venous thrombosis are recognized complications of pelvic lymph node dissection. Although the studies are conflicting, most have shown that some method of anticoagulation, low-dose heparin or pneumatic compression stockings, are beneficial in reducing the risk of these complications. We routinely administer subcutaneous heparin preoperatively and every 8 to 12 hours postoperatively as well as use pneumatic compression stockings until the patient is discharged.

Chronic lymphedema of the lower extremities and external genitalia may occur, and these may be worsened by radiotherapy or an extensive dissection. The modified pelvic lymph node dissection has been a reliable way of preventing chronic lymphedema.

Results

Staging pelvic lymphadenectomy is an essential part in the clinical evaluation of patients with prostate and bladder cancer. Within the obturator fossa, 87% of positive nodes will be detected. In patients with low-grade prostate cancer and with a PSA < 10, the incidence of positive nodes is so low that it may become prudent not to perform a pelvic node dissection as a separate procedure. In bladder cancer, the value of a node dissection may be to identify those patients in whom preoperative chemotherapy may be of benefit, though this remains to be shown in a clinical trial.

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