Development and Validation of a Nomogram Combining Ultrasound Parameters and Clinical Indicators for Predicting Sarcopenia in Breast Cancer Patients

Background: Sarcopenia, a condition prevalent among breast cancer patients, correlates with adverse treatment outcomes. To address the limited accessibility of gold-standard diagnostic methods, this study aimed to develop a practical nomogram based on gastrocnemius muscle ultrasound for sarcopenia screening in this population. Methods: This retrospective study enrolled 158 patients with primary breast cancer who were scheduled for TAC chemotherapy. We measured ultrasound parameters of the dominant medial gastrocnemius, including muscle thickness, pennation angle, and Young’s modulus in the relaxed state. Clinical data such as handgrip strength and age were also recorded. Sarcopenia was diagnosed on the basis of low handgrip strength combined with a low skeletal muscle index measured by computed tomography at the 12th thoracic vertebra level. Variables with P < 0.05 in the univariate analysis were entered into the multivariate logistic regression analysis to identify independent predictors, which were then used to construct the nomogram. The model underwent internal validation via the bootstrap method. Its discriminative ability, calibration, and clinical utility were assessed by the area under the receiver operating characteristic curve (AUC), calibration plots, and decision curve analysis, respectively. Results: Multivariate analysis revealed that muscle thickness, pennation angle, Young’s modulus in the relaxed state, and age were independent predictors of sarcopenia. The nomogram achieved an AUC of 0.911 (95% CI: 0.868–0.954). After internal bootstrap validation, the AUC remained high at 0.898, with sensitivity and specificity values of 86.1% and 72.6%, respectively. The calibration curve indicated good agreement between the predicted and observed probabilities. Decision curve analysis confirmed that the model yielded a net clinical benefit across a wide range of threshold probabilities. Conclusion: The nomogram integrating gastrocnemius ultrasound parameters and age has favorable predictive performance for sarcopenia in breast cancer patients, suggesting its potential as a practical screening tool in clinical practice. Trial registration: Not applicable.