To the best of our knowledge, this is the largest study on robotic transthoracic esophagectomy till date which represents the comprehensive experience from our institute. As the available data in the literature on this advancement is scarce, we feel that the present study perhaps will provide a better idea on the ‘real world’ scenario.
Esophagectomy for esophageal carcinoma is a technically challenging procedure associated with relatively high mortality and morbidity [7,12-14]. To reduce the morbidity as a result of surgical trauma from open procedures, minimal invasive procedures were introduced in the recent past. There are published reports that favored the use of MIE due to advantages of shorter operative time; reduced blood loss and shorter hospital stay [7,12,15-17]. Nevertheless, the conventional MIE methods are limited by the technical difficulties. Mainly, the use of long instruments with limited degree of freedom and two-dimensional view can become hindrance for optimal dissection [18,19].
The more recent introduction of robotic systems in surgical oncology has answered the limitations of MIE. Compared to the traditional minimally invasive procedures, robotic-assisted surgery offers several potential advantages. The improved visualization with the magnified three-dimensional view is of particular benefit that allows a precise and atraumatic dissection of the peri-esophageal tissue along the vital structures, such as pulmonary vein, trachea, thoracic duct, aorta and vagus nerve [9,20]. More importantly, the magnified view of the surgical field can assist in a more extensive dissection of the lymph nodes. The lymphatic spread of esophageal cancer is generally irregular due to submucosal lymphatic drainage system. The radical resection of esophagus with surrounding lymph nodes offers the best possible cure. With the use of robotic arms, we were able to achieve the mean lymph node yield of 18.36 (range 13 to 24). A study from van Hillegersberg R et al. harvested a median of 20 lymph nodes (range, 9–30) through robot-assisted thoracoscopic esophagectomy . Cerfolio et al. reported median number of 20 through the same approach . Galvani et al. achieved mean lymph nodes yield of 12 (range 7 to 27) using robot-assisted transhiatal esophagectomy . The same approach was utilized by Dunn et al., who harvested a median of 20 lymph nodes (range, 3–38) . Sarkaria et al. reported median number of 20 lymph nodes (range, 10–49) using combined thoracoscopic and laparoscopic robotic-assisted approach . We believe that the transthoracoscopic approach offers an outstanding access to the mediastinum and thereby allows an extended lymphadenectomy. When performing the procedure through the transhiatal approach, these potential metastatic lymph nodes might be leftover in situ . In fact, the R0 resection was achieved in 97.59% of our study population. Few other case series using the similar approach showed R0 resection rate varying from 76% to 100% [21,26,27].
The advantages of robotic surgery are more valuable when operating in the confined area, as in the esophageal surgery. The dexterity and articulated instruments permit seven degrees of motion including in/out; rotation; pitch at wrist; yaw at wrist; pitch at fulcrum; yaw at fulcrum and grip strength . The improved tremor free motion stability can add to fine movements and facilitate a precise dissection and suturing in a confined operating space. As a result, we enjoyed atraumatic dissection during the mediastinal dissection of the esophagus and surrounding lymph nodes. Additionally, we did not encounter any iatrogenic trauma during the procedure and achieved advantages in operative time and blood loss.
In comparison to previously reported studies, our study showed reduced total operating time. The total operating time of the procedure in our series was 204.94 mins. The first performed robotic-assisted esophagectomy in 2003 reported total operative time of 246 mins . Subsequent case series by van Hillgers et al. reported total operative time of 450 (range 370–550) min and thoracoscopic time of 180 (range 120–240) mins from experience in 21 patients . Boone et al. reported median operative time of 450 mins in a series of 47 patients . Some of the transhiatal approached had reported total operative time of 267.71 mins  and 311 mins . In the report from Sarkaria et al. the median total operative time was 556 min (range 395–807) . The relatively low total operative time in our series was a result of increased experience in robotic surgery, a well focused operating team as well as nursing staff’s familiarity with the procedures and equipments. We were able to reduce the docking time from 30 mins in initial days to 5 mins in the most recent case. This significant decrease represents the learning curve of the surgeon and team. The estimated blood loss was 86.75 ml in our study. Other publications have reported blood loss ranging from 40–625 ml using similar approach [9,21,27]. Papers focused on the transhiatal approach reported blood loss of 54 ml  and 97.2 ml . None of our patient required blood transfusion. This is of clinical significance as various studies have indicated that esophageal cancer patients with major blood loss receiving blood transfusions have a worse prognosis [29,30].
The mean ICU stay and hospital stay in our study was 1.2 days and 8 days, respectively. Other studies have reported ICU stay ranging from 1.8 day to 4 days [9,22,27] and hospital stay ranging from 8.7 days to 18 days [9,22-24,27]. Weksler B et al. compared the robotic esophagectomy with the traditional MIE and found no significant differences in operative time, blood loss, number of resected lymph nodes, length of ICU/hospital stay and postoperative complications .
In our study, we did not encounter any in-hospital mortality. Approximately, 80% of the patient population was alive at the median follow up of 10 months. There were no treatment related deaths. Two patients had recurrence of the cancer, one of which died while other was disease free following the further treatment. The complication rate was low in our study with reported complications in only 19.28% of the study population. In general, the transthoracic approach is more aggressive than the transhiatal approach and is more likely to cause cardiopulmonary complications, anastomotic and chylous leaks, vocal cord paralysis, and wound infection . However, a study by Satoh et al. has showed significantly reduced incidence of recurrent nerve palsy by robotic thoracoscopic esophagectomy in comparison to conventional thoracoscopic esophagectomy . Although, we encountered only two cases with recurrent nerve palsy, we advocate extreme caution during the en-bloc resection as there are chances of damaging recurrent nerve and its small branches that are located in the fatty tissue of the superior mediastinum. In our series, the post-operating complications reduced markedly in due course, with reported 3 cases anastomotic leak from first 32 cases in our previous publication  and no further incidences from last 51 cases. Similarly, there were no further cases of chyle leak from our last 51 cases.
A prospective randomized clinical trial is underway for comparing robot-assisted thoraco-laparoscopic esophagectomy with the open transthoracic esophagectomy . We are really hopeful that the trial will furnish the similar results to our study for robotic esophagectomy. If the trial hypothesis is proved, robot esophagectomy can be considered as treatment option related with a lower postoperative complications, lower blood loss and shorter hospital stay with at least similar oncologic outcomes and better postoperative quality of life .
The major drawback of the robotic system is the lack of haptic sensations. This limitation is mainly significant in procedures where touch is an important component. However, the recent surgical innovations are focused on the development of systems that transmits the haptic feedback to surgeon . As the surgeon works alone at a console, learning procedures and training to others can be sometimes challenging . Finally, the cost of the equipments could be additional limitation. However, robot- assisted surgery has already confirmed cost savings from minimal blood loss, morbidity and reduced hospital stay .