A nomogram for evaluation and analysis of difficulty in retroperitoneal laparoscopic adrenalectomy: A single-center study with prospective validation using LASSO-logistic regression

Abstract

Background: While it is known that inaccurate evaluation for retroperitoneal laparoscopic adrenalectomy (RPLA) can affect the surgical results of patients, no stable and effective prediction model for the procedure exists. In this study, we aimed to develop a computed tomography (CT) -based radiological-clinical prediction model for evaluating the surgical difficulty of RPLA.

Method: Data from 398 patients with adrenal tumors treated by RPLA in a single center from August 2014 to December 2020 were retrospectively analyzed and divided into sets. The influencing factors were selected by least absolute shrinkage and selection operator regression model (LASSO). Additionally, the nomogram was constructed. A receiver operating characteristic curve was used to analyze the prediction efficiency of the nomogram. The C-index and bootstrap self-sampling methods were used to verify the discrimination and consistency of the nomogram.

Result: The following 11 independent influencing factors were selected by LASSO: body mass index, diabetes mellitus, scoliosis, hyperlipidemia, history of operation, tumor diameter, distance from adrenal tumor to upper pole of kidney, retro renal fat area, hyperaldosteronism, pheochromocytoma and paraganglioma, and myelolipoma. The area under the curve (AUC) of the training set was 0.787, and 0.844 in the internal validation set. Decision curve analyses indicated the model to be useful. An additional 117 patients were recruited for prospective validation, and AUC was 0.848.

Conclusion: This study developed a radiological-clinical prediction model proposed for predicting the difficulty of RPLA procedures. This model was suitable, accessible, and helpful for individualized surgical preparation and reduced operational risk. Thus, this model could contribute to more patients' benefit in circumventing surgical difficulties because of accurate predictive abilities.

Keywords: LASSO; adrenalectomy; laparoscopy; nomogram; retroperitoneal space.

Figure 1

Study flowchart. (A) Inclusion and exclusion process; (B) Analysis and verification process; (C) Drawing of ROI and calculation of RFA.

Figure 2

Forest plot of influencing factors of surgical difficulty.

Figure 3

LASSO-Logistic regression. (A) The cross-validation results. (B) LASSO coefficient profiles of the 28 variables.

Figure 4

Nomogram of prediction model of difficulty of retroperitoneal laparoscopic adrenalectomy and its performance. (A) Nomogram. (B) Calibration curves of the nomogram in the training and internal validation sets. (C) ROC curves of the nomogram in the training, internal and prospective validation sets. (D) Clinical decision curve analysis of prediction model. (E) The calculated risk scores for each patient within the combined training and external validation datasets.) (NFAT, non-function adrenal tumor; PA, primary aldosteronism; PPGL, pheochromocytoma and paraganglioma; Others, include eosinophil tumor, teratoma, schwannoma, hematoma, tuberculoma, foreign body granuloma, retroperitoneal bronchial cyst, and hemangioma; MT, Malignant tumor, include adrenocortical carcinoma and adrenal metastasis; TD, tumor diameter; DAK, distance from adrenal tumor to upper pole of kidney; RFA, retrorenal fat area; BMI, body mass index.).