Minimally invasive oesophagectomy (MIE) is defined as a thoracoscopic-laparoscopic procedure for oesophageal cancer. MIE is considered to reduce postoperative pain, drainage volume and inflammation reactions, while shortening the hospital stay. However, MIE requires surgeons to have a deeper understanding of the endoscopic anatomy, surgical procedure, accidental bleeding, and lymph node dissection process, all of which may contribute to the operation quality. MIE has been performed since July 2010 in our department, and the improvements are clear based on bleeding volume, operation time, mortality within 3 months, and lymphadenectomy parameters. Our dataset showed that surgical process proficiency could be achieved through at least 57 surgeries with adequate lymph node dissection and favourable safety outcomes.
Ankit Dhamija reported the learning curve for lymph node resection in MIE for oesophageal cancer and suggested that the ability to dissect lymph nodes completely during MIE was affected by the surgeons’ experience, which might accumulate over time; a significant increase in experience could be achieved after the first 25 cases. The number of dissections was regarded as an important measurement of lymphadenectomy, and different lymphadenectomy thresholds were proposed based on various scholars’ findings. Dutkowski found that the diagnostic sensitivity of lymph node metastasis increased with an increasing number of dissections. When the dissection number reached 12, the sensitivity could reach at least 90%; at this point, more lymph node dissections only increased the complication rate since the diagnostic sensitivity reached a plateau. Rize believed that the ideal number of lymph node dissections should be no less than 18. There was no significant difference in the pathological characteristics between the 4 stages except for differentiation. Nonetheless, the numbers of lymph nodes dissected in each stage were 12.65 ± 4.13, 15.91 ± 3.36, 20.16 ± 7.71, and 22.67 ± 7.39, respectively, with a significant difference among the stages. To intuitively observe the upward trend, scatter plots were drawn, and the cumulative sum was calculated. In the present series, the inflection point was observed at the 57th case, which suggests that proficiency in lymphadenectomy during MIE was gained after 57 patients underwent the procedure. Significant increases were also discerned at both dissection numbers 12 and 18 during the 4 stages. Oncologic benefits were implied with this progress. These benefits were due to the actions implemented during the 2nd stage, including performing hybrid operations and attending academic communications.
MIE could be divided into a thoracoscopic-laparoscopic McKeown technique (cervical anastomosis) and a thoracoscopic-laparoscopic Ivor-Lewis technique (chest anastomosis). The former is preferred by surgeons because of the maturity of the surgical procedure, and the latter is not widely performed due to its difficulty and the risk of the occurence of a thoracic fistula; the surgical position and anastomosis type were also different in each clinical unit. However, the thoracoscopic-laparoscopic Ivor-Lewis method was suggested to be less invasive, with a shorter operation time, lower anastomotic leakage rate and lower recurrent laryngeal nerve injury rate than the thoracoscopic-laparoscopic McKeown method. In our series, an increase in the proportion of Ivor-Lewis procedures appeared during the 4th stage, which is after when the lymphadenectomy proficiency reached a relatively high level.
The importance of the surgical procedure were for accurate staging of the disease and an improvement in survival outcomes. The differences in 2-year overall survival and disease-free survival between the first three stages were not significant (72.2%, 67.7%, 68.01%, P = 0.9284) (66.7%, 58.06%, 59.6%, P = 0.7912), which may be due to the inadequate follow-up time and sufficient lymph node dissection, even when performed in the 1st stage (12.65 ± 4.13).
We retrospectively analysed 327 patients who underwent oesophagectomy for oesophageal cancer at our institution. A total of 157 patients underwent MIE (from the 3rd stage), and 170 patients underwent open oesophagectomy (OE). In our study, the MIE group had a smaller bleeding volume (P = 0.0000) and shorter operation time (P = 0.0132) than the OE group. There was no significant difference in the complication rates between the two groups; nonetheless, the MIE group had a lower incidence of postoperative pulmonary inflammation (12.1% vs. 29.4%, P = 0.0000), which is very similar to the results of the randomized controlled trial reported by Biere SS (12% vs. 34%, P = 0.005). Additionally, according to Parameswaran R and Verhage RJ, the postoperative respiratory complication rate of OE was higher than that of MIE. This result might be due to the large incision, rib fractures, respiratory muscle detachment, injury and repair of the diaphragm, and retention of sputum; thus, MIE was superior to OE in terms of protecting respiratory function.
The open group had more lymph nodes dissected than the MIE group (23.99 ± 10.15 vs. 21.26 ± 7.72, P = 0.0069); however, the number of lymph nodes dissected in the MIE group was similar to the results reported by another study. Lymph nodes were dissected from more sites in the MIE group than in the OE group (4.87 ± 1.43 vs. 4.16 ± 1.26, P = 0.0000), which might be due to the comprehensive view available with the thoracoscope. In the subgroup analysis, the dissection rate of the No.106rec (right or left) lymph nodes in the MIE group reached 78.4%, while that of the open group was 23.5% (P = 0.0000). The No.106rec (both right and left) lymph node dissection rate in the MIE group was 64.7%, which was significantly different from that of 7.1% in the open group (P = 0.0000). No.106tbL lymph node dissection followed a similar trend, and the MIE group had a statistically significant advantage over the OE group (31.8% vs. 16.5%, P = 0.001). Nonetheless, the open group had a statistical advantage (47.1% vs. 12.1%, P = 0.0000) in left gastric artery lymph node dissection, which reflects the capability limitations of the thoracic surgeon during laparoscopic abdominal lymphadenectomy.
Survival outcomes are crucial for the treatment of carcinoma. MIE is still not widely performed in medical institutions, and reports on long-term survival are rare. The 1-year survival rates between MIE and OE were demonstrated to have no significant differences. Jingpei Li reported that the 1-year, 2-year, and 3-year survival rates of patients who underwent MIE were not significantly different from those of patients who underwent the open procedure; however, the proportion of early-stage disease in the MIE group was higher than that in the open procedure group. A systematic review also provided information that the proportion of early-stage disease in the MIE group exceeded that in the open procedure group, which might be inevitable while the surgeons are still learning. Mitzman B performed a propensity analysis using data from the National Cancer Database of the United States, and equivalent oncological outcomes and survival outcomes were found for the MIE and open procedure groups. No significant differences in long-term survival were found in patients who underwent robotic-assisted minimally invasive oesophagectomy (RAMIE), MIE or OE; thus, surgeon expertise and experience might be considered the most important aspects. In our series, although the overall 2-year survival rate differed significantly between the groups (MIE group: 68%, open group: 43%, P = 0.0321), the proportion of stage III patients who underwent OE was statistically greater than that of patients who underwent MIE. This study did not provide evidence of improvements in the survival outcomes of patients who underwent MIE. As a result, a Cox proportional hazards regression was used to evaluate the effects of clinical factors on survival for patients who underwent radical surgery with curative intent. The clinical parameters included age, surgical procedure (MIE or open), differentiation degree (poor or middle-high), tumour excision area (≥ 5 cm or < 5 cm), infiltration depth (T1, T2, T3), and the number of positive lymph nodes. The maximum diameter of the tumour excision area and the number of positive lymph nodes had a significant influence on postoperative survival. There was no evidence that the surgical procedure (MIE or open) had a significant influence on the prognosis of patients with oesophageal cancer.
There are also some limitations to this study; the management of chest drainage and nasogastric drainage and inflammatory factors were not taken into account, but there are also important indicators for presenting a learning curve. Additionally, the number of lymph node was used as a reflection of lymphadenectomy completeness, and this number might be influenced by fracturing of the nodes or pathological diligence. Moreover, our study was a retrospective analysis, and challenging cases were avoided in the early stage of the learning process; thus, selection bias was inevitable. Finally, only a few patients received neoadjuvant therapy, which was recommended by the medical guidelines.
In conclusion, our findings provide evidence of the learning curve for MIE and its short-term benefits. However, there is still no evidence that MIE and OE contribute differently to postoperative survival outcomes.