Development and validation of a nomogram for predicting operating time in laparoscopic anterior resection of rectal cancer.

Aims: The goal of this study is to create and verify a nomogram estimate operating time in rectal cancer (RC) patients based on clinicopathological factors and MRI/CT measurements before surgery.

Materials and methods: The nomogram was developed in a cohort of patients who underwent laparoscopic anterior resection (L-AR) for RC. The clinicopathological and pelvis parameters were collected. Risk factors for a long operating time were determined by univariate and multivariate logistic regression analyses, and a nomogram was established with independent risk factors. The performance of the nomogram was evaluated. An independent cohort of consecutive patients served as the validation dataset.

Results: The development group recruited 159 RC patients, while 54 patients were enrolled in the validation group. Independent risk factors identified in multivariate analysis were a distance from the anal verge <5 cm (P = 0.024), the transverse diameter of the pelvic inlet (P < 0.001), mesorectal fat area (P = 0.017), and visceral fat area (P < 0.001). Then, a nomogram was built based on these four independent risk factors. The C-indexes of the nomogram in the development and validation group were 0.886 and 0.855, respectively. And values of AUC were the same with C-indexes in both groups. Besides, the calibration plots showed satisfactory consistency between actual observation and nomogram-predicted probabilities of long operating time.

Conclusions: A nomogram for predicting the risk of long operating duration in L-AR of RC was developed. And the nomogram displayed a good prediction effect and can be utilized as a tool for evaluating operating time preoperatively.