Robotic-Assisted Laparoscopic Partial Nephrectomy

Localized kidney cancer treatment overview

Kidney cancer (most commonly renal cell carcinoma) is one of the top ten commonly diagnosed cancers in men and women. ^[1]

While the incidence of renal cell carcinoma is increasing, there is also an increased rate of cancer detection because of the common use of cross-sectional imaging. As a result, many cancers are detected at earlier stages, ^[2] increasing the available treatment options. ^[3]

Evidence also shows that many small kidney cancers may be indolent and may progress slowly, ^[4] but there is no reliable method for predicting which patients will develop metastatic cancer. Although several systemic treatments have been developed in the last decade, the outcomes for metastatic renal cell carcinoma remain poor. ^[5] As a result, aggressive treatment is usually recommended in patients who do not have serious medical comorbidities. ^[6]

Surgery for localized renal cell carcinoma

In patients with renal cell carcinoma confined to the kidney (pathologic stage T1 or T2), surgery is effective treatment, with 5-year cancer-free rates of around 95% in large series. ^[1]

For 5 decades, the recommended treatment was complete removal of the kidney (radical nephrectomy), ^[2] which was effective but associated with an increased risk of chronic renal failure. ^[3]

Historically, partial nephrectomy was not offered as a standard treatment to otherwise healthy patients but was reserved for patients with a solitary kidney, poor renal function, or bilateral tumors. ^[4] However, in the 1990s, preserving renal function by removing only the tumor was popularized and accepted for selected patients with small renal masses.

To date, the vast majority of studies have shown equivalent cancer control in patients treated with complete removal of the kidney or removal of the tumor only, ^[6] with only rare exceptions. ^[7] In the American Urological Association (AUA) guidelines for small renal masses, when technically feasible, partial nephrectomy is the standard option for treatment of tumors less than 4 cm in otherwise healthy patients. ^[8]  The National Comprehensive Cancer Network (NCCN) recommends partial nephrectomy for a T1a renal mass, stating that radical nephrectomy should not be used when nephron-sparing approaches are possible. For T1b tumors, the NCCN guideline states that the standard of care is either radical nephrectomy or partial nephrectomy (when possible). ^[9]

In efforts to reduce the morbidity of open surgery, surgeons developed laparoscopic partial nephrectomy, with the initial large series showing excellent cancer-specific outcomes ^[10] but higher complication rates than open surgery. ^[11]

Other techniques that limit the morbidity of treatment for small renal cell carcinomas include active surveillance and laparoscopic or percutaneous ablation (cryoablation, radiofrequency ablation, and microwave ablation). ^[5] However, ablation techniques and surveillance have not demonstrated equivalent cancer outcomes to surgery and are not generally offered to otherwise healthy patients as first-line treatment.

With improvements in robotic technology for surgery, robotic-assisted partial nephrectomy (RPN) has emerged as a preferred technique, with excellent short-term cancer and functional outcomes and decreased morbidity in selected patients. ^[12]

Evolution of minimally invasive surgery for kidney cancer

Open nephrectomy for kidney tumors can be performed through a flank, subcostal, or midline abdominal incision.

The kidneys are located in the retroperitoneum deep to the colon and other peritoneal organs that may require a larger incision for proper access. In the 1980s and 1990s, reports of the feasibility of laparoscopic renal surgery were published, ^{[13, 14]} with the first hand-assisted laparoscopic nephrectomy performed in 1997. ^[15]

Laparoscopic techniques allowed smaller incisions, reduced postoperative pain, and hastened recovery. Multiple series have now demonstrated excellent long-term cancer outcomes for laparoscopic nephrectomy. ^[16] As laparoscopic techniques evolved, several authors demonstrated the feasibility ^[17] and favorable outcomes with laparoscopic partial nephrectomy performed by experienced laparoscopic surgeons. ^[18]

With the evolution of robotic technology for surgery, robotic-assisted partial nephrectomy has evolved as a technique that offers similar outcomes to laparoscopic or open techniques but that may have the advantage of improved maneuverability and precision to decrease ischemia times and improve postoperative renal function. ^[12]

Potential advantages and disadvantages of robotic assistance

The kidneys filter 10%-20% of an individual’s blood volume per minute. Therefore, partial nephrectomy requires precise control for excision and prompt repair to minimize bleeding and to decrease ischemic time to the kidney.

The robot offers two main advantages over conventional laparoscopy. First, the binocular camera allows the surgeon depth perception to easily operate in 3 dimensions. Second, the “wrist” of the robotic arms has 7 degrees of freedom, which allow the surgeon better control over certain aspects of the operation, most importantly precise suturing with minimal tissue manipulation. The technological advantages of robotic-assisted partial nephrectomy over conventional laparoscopy may allow novice surgeons a shorter learning curve. ^[19]

Several authors speculate that the technical difficulty of laparoscopic partial nephrectomy has precluded its widespread acceptance, whereas the technical improvements of robotic-assisted partial nephrectomy may allow even novice laparoscopic surgeons to safely perform minimally invasive partial nephrectomies. ^[20]

The most notable disadvantage of robotic-assisted partial nephrectomy is the added cost of purchasing and maintaining a surgical robot. In 2012, a new robot cost approximately $1.75 million, with a yearly service agreement of $150,000 (da Vinci Surgical System, Intuitive Surgical, Sunnyvale, CA). However, future research is needed to evaluate whether the increased cost of using the surgical robot may be offset by increased utilization of nephron-sparing surgery and better patient outcomes. ^{[21, 22]}

History of robotics in urology

The first use of a surgical robot was in orthopaedics in 1983, and the first use of robotics for urologic surgery was in 1988. Initial robots in urology were designed for transurethral surgery, laparoscopic camera holding, or endoscopic applications. ^[23] In 2000, the da Vinci robotic surgical system was approved by the US Food and Drug Administration, and the first robotic prostatectomy was performed the same year. ^[24] Surgeons quickly adopted this technique, and, by 2007, it is estimated that 60%-70% of all prostatectomies were performed using robotic assistance. ^[25]

For kidney surgery, robot assistance has been used for various types of surgery but has particular application to partial nephrectomy ^[26] and pyeloplasty ^[27] because of the ease of laparoscopic suturing compared to conventional laparoscopy.

Optimal patient selection for robotic assisted partial nephrectomy

As the understanding of renal cell carcinoma has evolved, the role of partial nephrectomy has expanded. Partial nephrectomy was originally offered only to patients with a solitary kidney, bilateral masses, or poor renal function. Gradually, partial nephrectomy became the standard of care among patients with renal masses smaller than 4 cm, and many surgeons argue that partial nephrectomy is currently the standard of care regardless of tumor size, when technically feasible. ^{[28]   [29]}

When deciding whether partial nephrectomy is feasible, the ability to safely remove all tumor completely is the primary consideration. The position of the tumor within the kidney with respect to the blood vessels and collecting system are of paramount importance when considering partial nephrectomy. Multiple systems have been developed to help standardize and make this judgement more objective. ^{[30, 31]   [32]}

The use of robotic assistance may facilitate better control when excising tumors and faster repair of the defect when the tumor is removed. Ideal tumors for robotic excision are exophytic and smaller than 4 cm. Larger tumors and those closer to hilar vessels decrease the ability to successfully perform robotic partial nephrectomy. However, larger central tumors may also be removed robotically based on the location of the tumor and experience of the surgical team. ^{[32, 29, 33]}

Other patient factors such as severe heart or lung disease may make the robotic approach less suitable.

Preoperative screening

Potential advantages of robotic-assisted partial nephrectomy include a 3-dimensional stereoscopic vision, articulating instruments, and scaled-down movements, reducing tremor. Such articulating instruments and increased freedom of movement may also allow the surgeon to quickly replicate the well-established open surgical maneuvers. ^[34] However, robotic-assisted partial nephrectomy is a technically challenging procedure because of the time constraints posed by hilar clamping. When the renal hilum is clamped, every minute of ischemia may decrease the patients subsequent renal function. ^[35] Therefore, the surgeon should be well versed with handling and troubleshooting the robotic interface. ^[36]

The preoperative screening for this relatively complex robot-assisted laparoscopic procedure is identical to that of a laparoscopic nephrectomy/partial nephrectomy. The evaluation is largely based on anesthesia risk and tumor stage, size, and location; any candidate suitable for a laparoscopic partial nephrectomy is suitable for a robot-assisted laparoscopic partial nephrectomy.

Preoperative evaluation should include stratification of cardiovascular risks, serum laboratory studies, and 3-dimensional imaging (CT or MRI) to accurately delineate the relationship of the mass to the renal vasculature and collecting system. ^[37] The number of renal vessels and any aberrant vasculature should be noted and may be further delineated with MRI.

Perioperative antibiotics may be given as per standard laparoscopic nephrectomy.

Nephron-sparing surgery is an established treatment for renal tumors smaller than 4 cm in diameter. ^[38] The standard open approach to partial nephrectomies has been permeated in recent years by laparoscopic surgery, allowing for a minimally invasive approach to this surgery. Furthermore, the indications for laparoscopic nephron-sparing surgery have expanded over the years, largely facilitated by robotic assistance. This technology has enabled overcoming the technical challenges and steep learning curve inherent to laparoscopic partial nephrectomies, ^[39] and several reports indicate that similar functional and oncologic outcomes can be achieved when compared to the standard open approach. ^{[40, 37]}

The general indications for an open partial nephrectomy apply to the robotic approach—bilateral synchronous or metachronous tumors, tumor in a solitary or solitary functioning kidney, or renal tumors as a manifestation of syndromes such as von Hippel-Lindau (VHL) disease or Birt-Hogg-Dubé (BHD) syndrome, given their multifocality and bilaterality.

While standard laparoscopic partial nephrectomy has been limited to relatively small exophytic tumors, robotic assistance permits nephron-sparing surgery for larger, more central, endophytic, and complex tumors that would otherwise be relegated to an open approach.

In experienced centers, robot-assisted laparoscopic partial nephrectomies have been performed for tumors larger than 4 cm ^[41] and central masses. ^[42] The main advantage with robotic assistance is its added dexterity and improved manipulation of the tumor, allowing for rapid control of postexcisional bleeding and renorrhaphy while minimizing blood loss and ischemia time. Accordingly, the indications for contemporary robotic partial nephrectomy are very similar to those of open partial nephrectomies in experienced hands, with comparable ischemic times, blood loss, and oncologic outcomes. Note that, while ischemic times approach those of open surgery, intraoperative parenchymal cooling cannot be applied during ischemia and tumor excision.

In general, robotic nephron-sparing surgery should not be offered for higher-stage tumors that are located in the hilum (ie, >T2, extension into vena cava, or with obvious nodal involvement). These parameters are generally assessed with preoperative CT- or MRI-based abdominal imaging.

When nephron-sparing surgery is absolutely indicated (ie, solitary kidney, bilateral tumors, renal insufficiency), some of these contraindications can be overlooked, especially in the hands of highly experienced surgeons. It should be kept in mind that the threshold to use the open approach or conversion to open should be held low in these complex scenarios. In addition, the standard relative contraindications to laparoscopic surgery (eg, significant prior abdominal surgeries, bowel obstruction) still apply to robot-assisted surgery.

The robotic approach to renal surgery, particularly partial nephrectomy, has some inherent challenges, and some familiarity with the da Vinci robotic system is necessary. The surgeon must gain an understanding of the robotic arm movements and range of motion, especially in relation to the clutch and camera.

Procedure Planning

In preparation for nephron-sparing surgery, the patient must undergo a complete metastatic workup, which involves abdominal imaging with CT or MRI, chest radiography, and blood work (complete blood cell count [CBC], electrolytes, liver and coagulation profile). The abdominal imaging should include reconstructed series to clearly delineate the vasculature, specifically the number and course of renal arteries and veins. This is critical to plan intraoperative hilar dissection and clamping.

In addition, tumor size, location, endophytic nature, and proximity to the collecting system are examined on preoperative imaging, and a renal nephrometry score is determined. ^[43] Arrangements should also be made for intraoperative ultrasonography to more precisely mark out the tumor prior to resection.

Of equal importance to the console surgeon is the bedside assistant, especially when applying the vascular clamps extra corporally. Sufficient assist ports must be placed prior to beginning dissection. All instruments, sutures, and pledgets should be carefully prepared prior to commencing the tumor excision; it would be prudent to “walk through” the procedure in detail with the bedside assistant, scrub nurse, and other operating-room personnel involved in the case.

Since 2004, more than 65 published articles have documented outcomes of robotic-assisted laparoscopic partial nephrectomy. Until recently, most studies were from a single institution and comprised small patient numbers. However, as the experience with the surgery has improved, so have outcomes. Furthermore, as surgeons have become more adept at performing this procedure, the ability to safely surgically remove renal masses in the hilar, endophytic, and multiple tumor locations has also improved. ^[44]

In the data in Table 1, the vast majority of renal masses excised were smaller than 4 cm (pT1a), and, as would be expected, approximately 70% were malignant. Operative times were longer than would be expected for open partial nephrectomy, and blood loss is similar across the series.

Table 1. Overall Demographics of Robotic-Assisted Laparoscopic Partial Nephrectomy (Open Table in a new window)

Concerning the data in Table 2, it should be noted that clamp times improved during the experience for each institution and averaged approximately 20 minutes overall.

Unlike traditional open partial nephrectomy, in which a kidney is normally cooled with ice for 10 minutes following clamping, laparoscopic and robotic partial nephrectomies are often performed with warm ischemia. Gettman et al ^[45] performed intra-arterial cooling of the renal artery in a few select patients. As the experience improved, some institutions began performing selective renal hilar arterial clamping or off clamp completely. Positive margin rates are similar to those reported for open partial nephrectomy.

Table 2. Warm Ischemia Time Associated With Renal Arterial Clamping and Positive Margin Rate (Open Table in a new window)

In Table 3, grade 1 and 2 complications included postoperative bleeding requiring transfusion, infection, and ileus. The most common Clavien 3 complications included urinoma requiring cystoscopy and stent placement and angioembolization.

Intraoperative complications were also rare and were primarily seen during procedures in which patients had prior abdominal procedures. Examples include enterotomy primarily repaired without sequelae and conversion to an open procedure. Tumor recurrences were uncommon across the board; however, most series had a limited follow-up.

Table 3. Postoperative Complications as Classified With the Clavien-Dindo system. (Open Table in a new window)

In Table 4, not all studies provided baseline and postoperative creatinine assessments. Some studies reported both 1-month and 6-month measurements overall. The estimated glomerular filtration rate (eGFR) was provided in several of the more recent studies and averaged a decrease of 5%. Overall, effects on renal function were minor, even in patients with multiple tumors. None of the studies reported the need for hemodialysis postoperatively.

Table 4. Assessment of Renal Function (Open Table in a new window)

Summary

Robotic partial nephrectomy achieves similar oncologic outcomes, less blood loss, minimal effects on renal function, and an excellent safety profile when performed at high-volume centers. Further studies with long-term cancer and functional outcomes may establish robotic-assisted partial nephrectomy as the standard of care for selected patients with small renal masses.