Thymectomy: Does The Robotic Approach Improve Outcomes For Non-thymomatous Myasthenia Gravis Patients?
Zhuoran Yao1, John K. Waters2, Hellen Chiou3, Allante Milsap1, Rachel Hurst4, Michael A. Wait2, Scott I. Reznik2, Michael E. Jessen2, Shaida Khan5, Steven Vernino5, Kemp H. Kernstine2.
1The University of Texas Southwestern Medical School, Dallas, TX, USA, 2Department of Cardiovascular and Thoracic Surgery, The University of Texas Southwestern Medical Center, Dallas, TX, USA, 3Department of Surgery, Rutgers Robert Wood Johnson Medical School, New Brunswick, NJ, USA, 4Department of Emergency Medicine, The Medical College of Wisconsin, Milwaukee, WI, USA, 5Department of Neurology, The University of Texas Southwestern Medical Center, Dallas, TX, USA.
BACKGROUND: Thymectomy has significantly altered the course of myasthenia gravis (MG). Few long-term outcomes have been reported for minimally invasive, especially robotic, thymectomy in treating non-thymomatous myasthenia gravis (NTMG). This study aimed to compare the outcomes of robotic (minimally invasive overall) vs. non-minimally invasive thymectomies for NTMG patients.
METHODS: A retrospective, IRB-approved single-institution review of thymectomies between 1/1/2006 and 6/21/2017 compared the indications, demographics, clinical data, outcomes, and hospital costs for different approaches. Long-term outcomes were assessed and managed by our neurologists. Perioperative outcomes were analyzed for all cases, with long-term outcomes evaluated for NTMG patients. MGFA post-intervention status (MGFA-PIS) was tracked postoperatively to assess long-term symptomatic changes. Pyridostigmine, mycophenolate, and prednisone requirements were followed for up to 10 years. There was no protocol for weaning medications. Chi-squared and Fisher's exact tests were used for categorical variables and two-tailed t and Mann-Whitney U tests for continuous variables with a threshold of p<0.05.
RESULTS: In 179 thymectomies (32% NTMG), the mean patient age was 47 years [14-82]. The patients were 64% female and 47% white. The thymectomies were 43% transsternal, 8% thoracoscopic, 11% transcervical, and 38% robotic. Compared to the 81 patients who underwent open thymectomies, those undergoing robotic thymectomies experienced 83% less blood loss (p<0.0001), 76% lower inpatient narcotic usage (p<0.0001), 48% lower ICU admission rates (p<0.0001), and 50% shorter hospital stay (p<0.0001), as shown in Table 1. Robotic thymectomies cost 53% less than transsternal ones (p=0.02). Preoperatively, in the 58 NTMG patients, 38% had MG for >24 months and 7% for <6 months. The median follow-up was 78 months [3-120]. Two recipients of robotic thymectomy (7%) and two of transsternal thymectomy (7%) achieved complete remission. There were no significant differences in long-term MG outcomes between minimally invasive (robotic & VATS) and open (transsternal) approaches in terms of changes in MGFA-PIS (Figure 1) and MG medication requirements (Figure 2a-d).
CONCLUSIONS: For NTMG, robotic thymectomy is associated with reduced perioperative blood loss, duration of stay, ICU admission, inpatient narcotic use, and inpatient costs without compromising long-term benefits when compared to non-minimally invasive approaches. To confirm these findings, a prospective trial is warranted. 
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