Partial nephrectomy with robot may be advantageous

August 1, 2010

A robot-assisted laparoscopic approach to partial nephrectomy maintains oncologic principles and renal function while offering several benefits compared with a conventional laparoscopic technique.

The analyses, reported at the AUA annual meeting, were based on 146 patients identified through propensity score matching, taking into account age, gender, body mass index, Charlson comorbidity index, preoperative renal function, imperative versus elective indication, and tumor characteristics (size, location, and proximity to the hilum).

Results showed that compared with the conventional group, patients operated on with the robotic technique had a significantly shorter mean operative time (213 vs. 271 minutes) and a significantly shorter hospital stay (3.2 vs. 4.1 days). The robotic group had a significantly longer, but still acceptable warm ischemia time compared with the conventional laparoscopy patients (25.9 vs. 15.0 minutes) that resulted in a significantly greater increase in serum creatinine at 2 weeks (21.5% vs. 10.0%). However, the increase from baseline serum creatinine was comparable in both groups at 3 months, and the postoperative decrease in estimated glomerular filtration rate was similar in the two groups at both follow-up intervals.

There were no significant differences between groups in rates of intraoperative or postoperative complications or transfusions, and the single case of a positive surgical margin was in the conventional group, reported first author Brian Irwin, MD, assistant professor of urology at the University of Vermont, Burlington.

"Minimally invasive nephron-sparing surgery for the treatment of small renal masses is increasingly being applied with robot-assisted platforms," Dr. Irwin said. "Using propensity-matched scoring to minimize any bias from differences between surgical groups, our study suggests robot-assisted and conventional laparoscopic partial nephrectomy are associated with very similar results."

The propensity-matched cohort was derived from consecutively operated patients undergoing partial nephrectomy by conventional (759 patients) or robot-assisted laparoscopy (103 patients) between 2006 and 2008 at two high-volume centers-Hartford Hospital, Hartford, CT, and Cleveland Clinic-where Institutional Review Board-approved laparoscopic databases are maintained.

Dr. Irwin noted that institutional differences in surgical technique may also be contributing to the procedure-related differences in warm ischemia time and length of hospital stays.

"Whereas most of the robotic procedures were done at Hartford Hospital, the conventional laparoscopy group was entirely from the Cleveland Clinic, where there was greater use of an 'early unclamping' technique," he told Urology Times.

Propensity matching reveals differences

Comparisons of the baseline demographic and clinical features of the two surgical groups showed several statistically significant differences that underline the value of using propensity matching to create comparable groups for the case-controlled analysis while also highlighting some logistical benefits of the robotic technique.

Compared with the conventional patients, the robot-assisted group had significantly higher proportions of central (62% vs. 50%), hilar (16% vs. 5%), and posterior (46% vs. 36%) tumors and a significantly lower mean Charlson index (0.73 vs. 1.06), Dr. Irwin reported.

"The robot-assisted technique has possible benefits for improved visualization and instrument articulation that should enable more precise excision and suturing. Our data on tumor characteristics and patient comorbidities, combined with the surgical outcomes, indicate that these features of robot-assisted laparoscopy allowed surgeons to successfully tackle more complex cases earlier in their learning curve. In fact, the overall patient accrual data showed a clear trend favoring a transition to the robotic technique over the 3-year study interval," he said.