Evaluation of the Iwate Model for Predicting the Difficulty of Laparoscopic Liver Resection: Does Tumor Size Matter?

Ranking as a Procedure for Selecting a Replacement Variable in the Score Predicting the Survival of Patients Treated with Curative Intent for Colorectal Liver Metastases

Background and Objectives: The issue of a missing variable precludes the external validation of many prognostic models. For example, the Liverpool score predicts the survival of patients undergoing surgical therapy for colorectal liver metastases, but it includes the neutrophil-lymphocyte ratio, which cannot be measured retrospectively. Materials and Methods: We aimed to find the most appropriate replacement for the neutrophil-lymphocyte ratio. Survival analysis was performed on data representing 632 liver resections for colorectal liver metastases from 2000 to 2020. Variables associated with the Liverpool score, C-reactive protein, albumins, and fibrinogen were ranked. The rankings were performed in four ways: The first two were based on the Kaplan-Meier method (log-rank statistics and the definite integral IS between two survival curves). The next method of ranking was based on univariate and multivariate Cox regression analyses. Results: The ranks were as follows: the radicality of liver resection (rank 1), lymph node infiltration of primary colorectal cancer (rank 2), elevated C-reactive protein (rank 3), the American Society of Anesthesiologists Classification grade (rank 4), the right-sidedness of primary colorectal cancer (rank 5), the multiplicity of colorectal liver metastases (rank 6), the size of colorectal liver metastases (rank 7), albumins (rank 8), and fibrinogen (rank 9). Conclusions: The ranking methodologies resulted in almost the same ranking order of the variables. Elevated C-reactive protein was ranked highly and can be considered a relevant replacement for the neutrophil-lymphocyte ratio in the Liverpool score. These methods are suitable for ranking variables in similar models for medical research.

Sub-classification of laparoscopic left hepatectomy based on hierarchic interaction of tumor location and size with perioperative outcomes

BACKGROUND

The aim of this multicentric study was to investigate the impact of tumor location and size on the difficulty of Laparoscopic-Left Hepatectomy (L-LH).

METHODS

Patients who underwent L-LH performed across 46 centers from 2004 to 2020 were analyzed. Of 1236 L-LH, 770 patients met the study criteria. Baseline clinical and surgical characteristics with a potential impact on LLR were included in a multi-label conditional interference tree. Tumor size cut-off was algorithmically determined.

RESULTS

Patients were stratified into 3 groups based on tumor location and dimension: 457 in antero-lateral location (Group 1), 144 in postero-superior segment (4a) with tumor size ≤40 mm (Group 2), and 169 in postero-superior segment (4a) with tumor size >40 mm (Group 3). Patients in the Group 3 had higher conversion rate (7.0% vs. 7.6% vs. 13.0%, p-value .048), longer operating time (median, 240 min vs. 285 min vs. 286 min, p-value <.001), greater blood loss (median, 150 mL vs. 200 mL vs. 250 mL, p-value <.001) and higher intraoperative blood transfusion rate (5.7% vs. 5.6% vs. 11.3%, p-value .039). Pringle's maneuver was also utilized more frequently in Group 3 (66.7%), compared to Group 1 (53.2%) and Group 2 (51.8%) (p = .006). There were no significant differences in postoperative stay, major morbidity, and mortality between the three groups.

CONCLUSION

L-LH for tumors that are >40 mm in diameter and located in PS Segment 4a are associated with the highest degree of technical difficulty. However, post-operative outcomes were not different from L-LH of smaller tumors located in PS segments, or tumors located in the antero-lateral segments.

JO, Gastaca M, Fondevila C, Efanov M, Rotellar F, Choi GH, Robles-Campos R, Wang. X, Sutcliffe RP, Pratschke J, Tang CN, Chong CC, D’Hondt M, Yong CC, Ruzzenente A, Herman P, Kingham TP, Scatton O, Liu R, Sandri GBL, Soubrane O, Mejia A, Lopez-Ben S, Monden K, Wakabayashi G, Cherqui D, Troisi RI, Yin M, Giuliante F, Geller D, Sugioka A, Edwin B, Cheung TT, Long TCD, Abu Hilal M, Fuks. D, Chen. KH, Aldrighetti L, Han HS, Goh BKP. Impact of tumor size on the difficulty of laparoscopic left lateral sectionectomies

BACKGROUND

Tumor size (TS) represents a critical parameter in the risk assessment of laparoscopic liver resections (LLR). Moreover, TS has been rarely related to the extent of liver resection. The aim of this study was to study the relationship between tumor size and difficulty of laparoscopic left lateral sectionectomy (L-LLS).

METHODS

The impact of TS cutoffs was investigated by stratifying tumor size at each 10 mm-interval. The optimal cutoffs were chosen taking into consideration the number of endpoints which show a statistically significant split around the cut-points of interest and the magnitude of relative risk after correction for multiple risk factors.

RESULTS

A total of 1910 L-LLS were included. Overall, open conversion and intraoperative blood transfusion were 3.1 and 3.3%, respectively. The major morbidity rate was 2.7% and 90-days mortality 0.6%. Three optimal TS cutoffs were identified: 40-, 70-, and 100-mm. All the selected cutoffs showed a significant discriminative power for the prediction of open conversion, operative time, blood transfusion and need of Pringle maneuver. Moreover, 70- and 100-mm cutoffs were both discriminative for estimated blood loss and major complications. A stepwise increase in rates of open conversion rate (Z = 3.90, P < .001), operative time (Z = 3.84, P < .001), blood loss (Z = 6.50, P < .001), intraoperative blood transfusion rate (Z = 5.15, P < .001), Pringle maneuver use (Z = 6.48, P < .001), major morbidity(Z = 2.17, P = .030) and 30-days readmission (Z = 1.99, P = .047) was registered as the size increased.

CONCLUSION

L-LLS for tumors of increasing size was associated with poorer intraoperative and early postoperative outcomes suggesting increasing difficulty of the procedure. We determined three optimal TS cutoffs (40-, 70- and 100-mm) to accurately stratify surgical difficulty after L-LLS.

Utility of the Iwate difficulty scoring system for laparoscopic right posterior sectionectomy: do surgical outcomes differ for tumors in segments VI and VII?

INTRODUCTION

The Iwate Score (IS) have not been well-validated for specific procedures, especially for right posterior sectionectomy (RPS). In this study, the utility of the IS was determined for laparoscopic (L)RPS and the effect of tumor location on surgical outcomes was investigated.

METHODS

Post-hoc analysis of 647 L-RPS performed in 40 international centers of which 596L-RPS cases met the inclusion criteria. Baseline characteristics and perioperative outcomes of patients stratified based on the Iwate score were compared to determine whether a correlation with surgical difficulty existed. A 1:1 Mahalanobis distance matching was utilized to investigate the effect of tumor location on L-RPS outcomes.

RESULTS

The patients were stratified into 3 levels of difficulty (31 intermediate, 143 advanced, and 422 expert) based on the IS. When using a stepwise increase of the IS excluding the tumor location score, only Pringle's maneuver was more frequently used in the higher surgical difficulty level (35.5%, 54.6%, and 65.2%, intermediate, advanced, and expert levels, respectively, Z = 3.34, p = 0.001). Other perioperative results were not associated with a statistical gradation toward higher difficulty level. 80 of 85 patients with a segment VI lesion and 511 patients with a segment VII lesion were matched 1:1. There were no significant differences in the perioperative outcomes of the two groups including open conversion, operating time, blood loss, intraoperative blood transfusion, postoperative stay, major morbidity, and mortality.

CONCLUSION

Among patients undergoing L-RPS, the IS did not significantly correlate with most outcome measures associated with intraoperative difficulty and postoperative outcomes. Similarly, tumor location had no effect on L-RPS outcomes.

A machine learning analysis of difficulty scoring systems for laparoscopic liver surgery

INTRODUCTION

In the last decade, several difficulty scoring systems (DSS) have been proposed to predict technical difficulty in laparoscopic liver resections (LLR). The present study aimed to investigate the ability of four DSS for LLR to predict operative, short-term, and textbook outcomes.

METHODS

Patients who underwent LLR at a single tertiary referral center from January 2014 to June 2020 were included in the present study. Four DSS for LLR (Halls, Hasegawa, Kawaguchi, and Iwate) were investigated to test their ability to predict operative and postoperative complications. Machine learning algorithms were used to identify the most important DSS associated with operative and short-term outcomes.

RESULTS

A total of 346 patients were included in the analysis, 28 (8.1%) patients were converted to open surgery. A total of 13 patients (3.7%) had severe (Clavien-Dindo ≥ 3) complications; the incidence of prolonged length of stay (> 5 days) was 39.3% (n = 136). No patients died within 90 days after the surgery. According to Halls, Hasegawa, Kawaguchi, and Iwate scores, 65 (18.8%), 59 (17.1%), 57 (16.5%), and 112 (32.4%) patients underwent high difficulty LLR, respectively. In accordance with a random forest algorithm, the Kawaguchi DSS predicted prolonged length of stay, high blood loss, and conversions and was the best performing DSS in predicting postoperative outcomes. Iwate DSS was the most important variable associated with operative time, while Halls score was the most important DSS predicting textbook outcomes. No one of the DSS investigated was associated with the occurrence of complication.

CONCLUSIONS

According to our results DDS are significantly related to surgical complexity and short-term outcomes, Kawaguchi and Iwate DSS showed the best performance in predicting operative outcomes, while Halls score was the most important variable in predicting textbook outcome. Interestingly, none of the DSS showed any correlation with or importance in predicting overall and severe postoperative complications.

The learning curve of laparoscopic liver resection utilising a difficulty score

BACKGROUND

This study aimed to quantitatively evaluate the learning curve of laparoscopic liver resection (LLR) of a single surgeon.

PATIENTS AND METHODS

A retrospective review of a prospectively maintained database of liver resections was conducted. 171 patients undergoing pure LLRs between April 2008 and April 2021 were analysed. The Halls difficulty score (HDS) for theoretical predictions of intraoperative complications (IOC) during LLR was applied. IOC was defined as blood loss over 775 mL, unintentional damage to the surrounding structures, and conversion to an open approach. Theoretical association between HDS and the predicted probability of IOC was utilised to objectify the shape of the learning curve.

RESULTS

The obtained learning curve has resulted from thirteen years of surgical effort of a single surgeon. It consists of an absolute and a relative part in the mathematical description of the additive function described by the logarithmic function (absolute complexity) and fifth-degree regression curve (relative complexity). The obtained learning curve determines the functional dependency of the learning outcome versus time and indicates several local extreme values (peaks and valleys) in the learning process until proficiency is achieved.

CONCLUSIONS

This learning curve indicates an ongoing learning process for LLR. The proposed mathematical model can be applied for any surgical procedure with an existing difficulty score and a known theoretically predicted association between the difficulty score and given outcome (for example, IOC).