What is a pelvic lymph node dissection and what are the risks?

If it goes outside of the prostate, the first location to which prostate cancer tends to spread is the pelvic lymph nodes. It is important to know whether the cancer has spread to the lymph nodes because the success rates of treatments such as interstitial seed therapy and radical prostatectomy are lower if the cancer has spread into the pelvic lymph nodes. Thus, the urologist or radiation oncologist should have a good idea whether there is prostate cancer involvement of the pelvic lymph nodes before recommending a therapy. Unfortunately, radiologic studies such as CT scans have not been helpful in identifying individuals with smaller amounts of cancer in the pelvic lymph nodes. CT or MRI may be warranted for staging men with high-risk clinically localized prostate cancer and PSA values > 20.0 ng/ml or when the Gleason score is greater than or equal to 8.

The most accurate way to assess the lymph node status is to remove the lymph nodes and have them examined by the pathologist. The lymph nodes to which prostate cancer typically spreads are located in the lateral aspect of each side of the pelvis (see Question 12). Removing the lymph nodes requires surgery, either an open procedure or a laparoscopic procedure, and has risks. The use of the ProstaScint scan to detect prostate cancer in the pelvic lymph nodes is being evaluated.

Not everyone needs a pelvic lymph node dissection. When the risk of having positive lymph nodes is low, such as occurs in men with a low Gleason score and a PSA < 10 ng/ml, a lymph node dissection is unnecessary, and one can proceed directly with definitive therapy, such as interstitial seed therapy, external beam radiation therapy (EBRT), and radical prostatectomy. In high-risk patients, those with higher Gleason scores (8-10), or those with a PSA > 10 ng/ml, a lymph node dissection may be performed at the same time as a planned radical prostatectomy, before planned EBRT, or before interstitial seed therapy. If an open prostatectomy or laparoscopic robotic prostatectomy is planned, the lymph nodes can be removed using the same approach as for the prostatectomy and can be examined by the pathologist (frozen section) just before the prostatectomy. Frozen section specimens are interpreted by the pathologist shortly after they are removed from the patient, and the findings are reported to the surgeon in the operating room. The surgeon then decides whether to proceed with removal of the prostate based on whether cancer has been identified in the lymph nodes. Some surgeons remove the prostate in the presence of small amounts of cancer in the lymph nodes, whereas others do not. The slides are then made into permanent sections and reviewed again by the pathologist. In most cases, the interpretation of the frozen section is the same as that of the permanent section; rarely do the two differ. In a perineal prostatectomy, the perineal incision does not allow access to the pelvic lymph nodes, and a separate midline incision or a laparoscopic approach is needed for the lymph node dissection. With EBRT or interstitial seed therapy, the pelvic lymph node dissection may be performed laparoscopically or via an open incision that is located below the umbilicus on a separate day, before EBRT/interstitial seeds.

A lymph node dissection should be performed in high-risk patients because it may affect treatment. The likelihood of having positive nodes varies with the stage of the prostate cancer, the PSA value, and the Gleason score. Approximately 5-12% of men who are believed to have clinically localized prostate cancer (low stage) have cancer that has spread to the pelvic lymph nodes. Before the pelvic lymph node dissection, you should discuss with your doctor how your planned prostate cancer treatment would be affected if you had cancer involving the pelvic lymph nodes.

The main risks of a pelvic lymph node dissection are bleeding, nerve injury, and lymphocele. The obturator nerve supplies muscles in the leg and is surrounded by some of the pelvic lymph nodes. If this nerve is damaged at the time of surgery and not repaired, it may lead to permanent inability to cross your leg on the side of the injury. A lymphocele is a collection of lymph fluid that accumulates in the pelvis, resulting from injury the lymph vessels. Lymphoceles require treatment if they are large and causing pressure/pain and/or become infected. Usually they can be drained by placing a small drainage tube through the skin into the lymphocele.

Before the pelvic lymph node dissection, you should discuss with your doctor how your planned prostate cancer treatment would be affected if you had cancer involving the pelvic lymph nodes.