Laparoscopic colorectal resection (LCR) is gaining popularity. Prospective randomized control studies have revealed some benefits of LCR for colorectal cancer compared with open surgery [1–5]. Nonetheless, open surgery remains an important technique. Thus, surgeons should be technically proficient in both open and laparoscopic surgery.

LCR is believed to be technically more difficult than open surgery and thought to require more intensive training to ensure safe and oncologic operation [6, 7]. There are many reports regarding the learning curve for performing LCR [7–15]. The learning curve is generally accepted to be approximately 30 procedures based on decline in operative time, intraoperative complications, and conversion rate. One question however remains unanswered: Can training for open and LCR occur simultaneously?

We hypothesized that surgeons who have finished a basic 4-year surgical residency program according to the Japanese system can learn both open and laparoscopic colorectal cancer resection efficiently simultaneously as long as they are well supervised. The objective of this study is to review the learning curve for open and laparoscopic colon resection of one surgeon who underwent a rigorous training program.

Patients and methods

A review of consecutive patients who underwent surgery for colon and rectosigmoid junction cancers from May 2005 to December 2007 by one trainee surgeon at Jichi Medical University Saitama Medical Center was performed. This surgeon had completed his basic surgical residency but had limited experience in colorectal cancer surgery and D3 dissection. Prior to commencement of the colorectal training, this surgeon had performed 350 cases of general surgery operations as first surgeon, including 80 cases of appendectomy, 62 cases of hernia repair, 46 cases of laparoscopic cholecystectomy, 10 cases of gastrectomy, and 21 cases of colectomy. Colectomies included five cases of ileocecal resection, nine cases of sigmoid colectomy, and seven cases of right hemicolectomy. He had also been an assistant in more than 1,000 other cases during a 4-year surgical residency program in Japan.

Because this study was designed to investigate the learning curve for laparoscopic and open colorectal surgery under supervision by experts, difficult cases were excluded from this study. Exclusion criteria were as follows: (1) patients who underwent combined procedures such as cholecystectomy, hepatectomy, and hysterectomy, (2) tumor located near the splenic flexure or in the rectum, and (3) T4 tumors that directly invaded adjacent organs or structures. In total, 75 patients were included in this study. All operations were supervised by at least one staff surgeon with experience of more than 300 LCR cases. The trainee surgeon was allowed to train in both laparoscopic and open colorectal resection simultaneously. When the surgeon performed more than 80% of the procedure, it was credited to this surgeon. Patient characteristics and oncological outcomes were analyzed.

Standardized procedures were performed for all cases. For left-sided lesions, medial-to-lateral approach was performed in laparoscopic surgery, while lateral-to-medial approach was done in open surgery. Laparoscopic left-sided colon resection began with ligation of proximal vascular pedicles, followed by mobilization and resection of bowel with anastomosis. For right-sided lesions, both procedures were performed using lateral-to-medial approach, which began with mobilization of the bowel, followed by exploration of the retroperitoneum, ligation of vascular pedicles, and resection of bowel with anastomosis. D3 dissection (exposure of the root of the feeding vessels) was performed when indicated.

Quality assessment and analysis of learning curve was performed by plotting cumulative summation (CUSUM) curves, and the moving average method was used to assess changes in operation time for both laparoscopic surgery and open surgery. CUSUM curve has emerged as a popular tool to monitor quality of surgery [16]. CUSUM allows one to judge whether a given variation in performance is acceptable, or whether the variation is greater than could be expected from random variation and thus may be a concern. As previous report utilized CUSUM to assess the learning curve for surgical treatment, CUSUM (S n ) was defined as S n  = Σ(X i  − X 0), where X i is an individual attempt and X 0 is the predetermined acceptable failure rate for the procedure, with X i assigned a score of 0 for success and 1 for failure [13, 14]. The acceptable failure rate was defined such that, when the target success rate was set at 90%, the acceptable failure rate was 10% (X 0 was set at 0.1). For the CUSUM curve we defined “failure” has occurring when any of the following occurred: (1) perioperative major morbidity and mortality, (2) intraoperative blood loss >1,000 ml, or (3) long operative time more than two standard deviations above the department average (>240 min for open surgery, >270 min for LCR).

The moving average method was also used to assess changes in operation time for qualification of the learning curve. Creating an average of values that moves with the addition of new data results in smoothing of the value of the variable being analyzed.

Statistical analysis was performed using SPSS version 17.0 (SPSS Inc., Chicago, IL) for Windows. The chi-square test or Fisher’s exact test was used for comparison of categorical variables as appropriate, and Student’s t-test was used for comparison of continuous variables. Values of p < 0.05 were regarded as statistically significant.

Results

A total of 75 patients were included in this study. The choice of surgical procedure was basically determined by patient preference, with LCR performed as default. Consequently, 43 patients underwent laparoscopic resection, while 32 patients underwent open surgery. Patient characteristics are presented in Table 1. Age, mean BMI, American Society of Anesthesiologists (ASA) score, and history of past abdominal surgery showed no significant difference between laparoscopic and open groups.

Table 1 Patient demographics: comparison between laparoscopic and open cases
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Tumor characteristics are listed in Table 2. There were no differences in tumor stage (UICC) or tumor size (p = 0.068 and 0.194, respectively). Extent of lymph node involvement or distant metastasis did not show significant difference. There were a significantly larger number of harvested lymph nodes in the laparoscopic group (p = 0.012). Operative outcomes are listed in Table 3. In laparoscopic surgery, operative time was significantly longer, while estimated blood loss was significantly less. The morbidity rate for open and laparoscopic surgery was 3.1% (1/32) and 4.7% (2/43), respectively (p = 0.484). Morbidities were small bowel obstruction for open surgery, and major leakage and bleeding that required blood transfusion for laparoscopic surgery. Mortality rate was 0% in both groups during this study. There were three cases of conversion to open surgery from initially performed laparoscopic surgery during this study; reasons for conversion were severe small bowel adhesion to abdominal wall due to previous laparotomy for duodenal ulcer in one case, and two cases of bleeding which were difficult to control by laparoscopic operation.

Table 2 Tumor characteristics: comparison between laparoscopic and open cases
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Table 3 Operative outcomes
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The moving average of the operation time for open and laparoscopic surgery is shown in Fig. 1. For both groups, operation time decreased with increasing experience, and plateaued after 25 cases in the laparoscopic group and 22 cases in the open group.

Fig. 1
figure 1

Moving average of the operating time

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CUSUM curves are shown in Fig. 2. In the laparoscopic group, surgical morbidity was observed in two cases, and operative time was longer than 270 min in five cases. In the open group, surgical morbidity occurred in one case, and operative time exceeded 240 min in three cases. There were no cases exceeding 1,000 ml blood loss in either approach. The learning curve for open cases was 11 cases and 7 for laparoscopic surgery.

Fig. 2
figure 2

Cumulative summation (CUSUM) score; upward slopes indicate that at least one failure was recorded in the case index number. Case was scored as +0.9 for failure or −0.3 otherwise, then the score was sequentially added

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Discussion

The 4-year basic surgical residency program in Japan involves attainment of basic surgical skills. Basic surgical residents start with basic procedures such as appendectomy, cholecystectomy, and hernia repair [17–21]. They then progress to open colorectal cancer surgery. LCR is learned later, after proficiency in open colorectal resections. With efforts to standardize LCR technique and supervision from expert surgeon in LCR, it has become easier for a trainee surgeon to learn the technical skills of LCR. We thus hypothesized that LCR could be learned simultaneously with open colorectal surgery.

In this study, we excluded tumors that were located near the splenic flexure, at the descending colon, and the rectum, as these locations are technically more difficult and may not be suitable for operation by trainee. Cases of tumors that were invading adjacent organs were also excluded for similar reasons.

Previous reports evaluating the learning curve of laparoscopic colorectal surgery included some different factors from those utilized herein [7, 9, 13, 22, 23]. To evaluate quality of LCR, we did not include number of lymph nodes harvested, as standard D2 or D3 operations for early and advanced tumors, respectively, were performed in all cases. Extent of dissection was ensured by the supervisor in every case. Conversion to open surgery was also not included in this study. In our previous study, trainee surgeon did not cause more conversion in LCR if they were well supervised [24]. So, we do not believe that conversion to open surgery is a good indicator to assess quality of LCR under good supervision. Besides, conversion rate should be evaluated as proficiency of laparoscopic surgery only. We considered blood loss more than 1,000 ml and long operative time as failure, as our previous study showed that these were independent predictors of poorer outcome (data to be published in the American Journal of Surgery).

Monitoring quality in surgical treatment has been a topic of interest for many. Direct observation by a supervisor and graphical representation of the learning curve are two common ways of assessing individual competence, but both are likely to be subjective [25, 26]. Assessment of surgeon competency should be dynamic and enable quantitative and continuous evaluation of surgeon performance. CUSUM allows continuous monitoring of surgical performance using clearly defined situations of failure and provides objective evaluation. CUSUM has emerged as a popular tool for performance monitoring in surgery since its first application to evaluate surgical outcomes by de Leval et al. [27]. CUSUM methodology has been applied to describe quality in colorectal surgery in several studies [8, 13, 14]. In this study, the CUSUM curve demonstrated downward slope after 11 cases in open group and 7 cases in laparoscopic group, which implies that the surgeon had acquired sufficient skills for index procedures.

The moving time average stabilized after 25 cases for laparoscopic colorectal surgery and 22 cases for open surgery, which implies that a further 18 and 11 cases were required to stabilize operation time in laparoscopic and open surgery, respectively. These patterns suggest that the trainee surgeon was able to perform the procedure safely at an early stage, and this was then followed by reduction in operative time when technical skills were further improved.

The learning curve for LCR in our study was similar to one previous report [13], while other reports demonstrated larger number of cases for the learning curve [7, 10, 12, 15]. The accelerated learning curve demonstrated herein is likely to be a result of the following: Firstly, the trainers in this series were extremely experienced in both laparoscopic and open colorectal surgery. Each of the trainers had carried out more than 300 cases of LCR. With this experience, it was possible for them to impart a technique for both open and laparoscopic surgery that has already been well established and standardized. This enabled easier learning, as the trainee did not have to contend with different techniques of different supervising surgeons. Secondly, the ever-present supervision of the experienced staff surgeons enabled the trainee to commit fewer mistakes intraoperatively, especially in identification of anatomical structures and planes of dissection. Furthermore, the radicality of oncologic surgery was maintained [24].

Conclusions

Surgeons who have completed basic surgical residency but have limited colorectal surgery experience can learn both open and laparoscopic colorectal surgery simultaneously in an effective manner under supervision by well-experienced surgeons.