Robotic prostatectomy (RP) is a common surgical procedure for prostate cancer, involving the precise removal of the prostate gland using a minimally invasive, robot-assisted approach. Pelvic Lymph Node Dissection (PLND) is a separate surgical step performed concurrently with the robotic prostatectomy in certain cases, but it is not automatic for every patient. Whether lymph nodes are removed depends entirely on the likelihood that cancer cells have already spread beyond the prostate capsule. This determination is based on a careful assessment of the individual patient’s risk factors for nodal involvement.
The Function of Lymph Nodes in Cancer Staging
Lymph nodes are small, bean-shaped organs that function as filters within the lymphatic system. For prostate cancer, the lymphatic system represents a primary pathway for cancer cells to travel and establish new tumors outside the prostate gland. When cancer cells break away from the primary tumor, they often enter these lymphatic vessels and lodge in the closest lymph nodes in the pelvis, such as the obturator, internal iliac, and external iliac nodes.
The status of these lymph nodes is a fundamental component of cancer staging, specifically the “N” (Node) part of the widely used Tumor, Node, Metastasis (TNM) system. Finding cancer cells in these nodes, known as N1 disease, indicates that the disease has progressed beyond the localized stage. This pathological information provides a more accurate prognosis and helps determine whether additional treatments, such as hormone therapy or radiation, may be necessary after surgery. Proper surgical staging via lymph node dissection is currently the most accurate method to detect these small deposits of cancer cells.
Patient Risk Assessment and Surgical Strategy
The decision to perform a pelvic lymph node dissection during robotic prostatectomy is made pre-operatively, based on a patient’s estimated risk of having cancer spread to the nodes. Surgeons use validated tools called nomograms, which incorporate several pathology and clinical factors to predict the probability of nodal involvement. The primary factors considered include the pre-operative Prostate-Specific Antigen (PSA) blood level, the clinical T-stage (which describes the size and extent of the primary tumor), and the Gleason Grade Group (which reflects the aggressiveness of the cancer cells).
For patients categorized as very low-risk or low-risk, the probability of finding cancer in the lymph nodes is typically less than 2%. Current guidelines often recommend omitting the lymph node dissection entirely. This approach is favored because the staging information gained is minimal, and avoiding the procedure eliminates the risk of its specific complications. However, for intermediate-risk and high-risk patients, the likelihood of nodal metastasis rises significantly, and a dissection is almost always performed.
The extent of the dissection is also determined by risk, distinguishing between a “Limited/Standard” and an “Extended” Pelvic Lymph Node Dissection (PLND). Standard PLND typically involves removing lymph nodes only from the obturator fossa and external iliac regions. An Extended PLND (ePLND) is performed for higher-risk disease and includes a wider template, encompassing the internal iliac, common iliac, and sometimes the presacral nodes. Extended dissection removes a greater number of nodes compared to a standard approach, and has a greater chance of detecting occult metastases, which provides more precise staging information. The robotic platform’s precision and magnification facilitate the meticulous dissection required for an extended template.
Potential Complications of Lymph Node Dissection
While lymph node dissection provides important staging and potential therapeutic benefits, it carries unique risks separate from the radical prostatectomy itself. The most common complication is the formation of a lymphocele, which is a collection of lymphatic fluid that accumulates in the pelvis where the nodes were removed. Lymphoceles are often asymptomatic and resolve on their own, but if they grow large, they can cause pain, pressure, or become infected, sometimes requiring drainage.
Another specific risk is lymphedema, which is chronic swelling that typically affects the legs or genital area. This occurs because the removal of lymph nodes disrupts the normal drainage pathways of lymphatic fluid, causing it to pool in the tissues. Surgeons must also take care during the dissection to avoid injury to nearby structures, particularly the obturator nerve, which controls some movement and sensation in the inner thigh. Injury to this nerve can result in temporary or permanent weakness in the leg.