Development and Internal Validation of a Clinical Data-Based Machine Learning Web Calculator for Predicting Recurrence in Granulomatous Lobular Mastitis: A Multicenter Retrospective Study.

Objective: Granulomatous lobular mastitis (GLM) is a disease characterized by a high recurrence rate and the absence of a standard treatment, making prognostic prediction crucial. While promising, existing machine learning models are limited by single-center data and small sample sizes. This study aimed to develop and validate machine learning models using a large multicenter dataset to predict GLM recurrence and build a clinical web calculator. Materials and Methods: In this retrospective cohort study, data from 318 GLM patients at two tertiary hospitals (diagnosed between 2019 and 2024) were used to train and evaluate five machine learning models. Performance was assessed by accuracy, area under the curve (AUC), F1-score, sensitivity, and specificity. Results: The five models demonstrated comparable discriminatory performance, with AUCs ranging from 0.778 to 0.808 and no statistically significant differences among them. Among them, random forest (RF) excelled in composite and sensitivity metrics (F1 score: 0.639; accuracy: 76.2%; sensitivity: 50%), whereas logistic regression achieved the top AUC (0.808), and the support vector machine achieved the best specificity (95.3%). Based on its balanced performance across multiple metrics, RF was selected for deployment to develop a publicly accessible web application platform (https://w12251393.shinyapps.io/predictGLM/). In the RF model, white blood cell count emerged as the top predictor, followed by age at diagnosis, the origin of the primary tumor, surgical excision, antitubercular therapy, corticosteroid therapy, and abscess drainage, in descending order of importance. Conclusion: Although retrospective in design, this study developed a multicenter RF model and implemented it as an accessible web calculator, providing a valuable tool for personalized recurrence prediction and treatment decision-making in GLM. The model should be used as a risk stratification aid to support clinical decision-making rather than as a definitive predictive instrument.