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Erschienen in:
01.02.2007
Predicting Patients at Low Probability of Requiring Postmastectomy Radiation Therapy
Erschienen in: Annals of Surgical Oncology | Ausgabe 2/2007
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Background
Postmastectomy radiation therapy (PMRT) is recommended for patients with four or more positive lymph nodes (LN+). Given the ramifications of PMRT for immediate reconstruction, we sought to create a model using preoperative and intraoperative factors to predict which patients with a positive sentinel lymph node will have less than four LN+.
Methods
The database from a prospective multicenter study of 4,131 patients was used for this analysis. Patients with one to three positive sentinel lymph nodes (SLN) and tumors < 5 cm (n = 1,133) in size were randomly divided into a training set (n = 580) and a test set (n = 553). Multivariate logistic regression was used on the training set to create a prediction rule that was subsequently validated in the test set.
Results
Median patient age was 57 (range, 27–100) years, and median tumor size was 2.0 (range, 0.2–4.8) cm. In the training set, factors associated with having four or more LN+ on multivariate analysis were: tumor size [odds ratio (OR) = 2.087; 95% confidence interval (CI): 1.307–3.333, P = 0.002), number of positive SLN (P < 0.0005), and proportion of positive SLN (OR = 3.602; 95% CI: 2.100–6.179, P < 0.005). A predictive model was established with a point assigned to each positive SLN, T2 (vs. T1), and if proportion of positive SLN was > 50%, for a maximum of five points. In both the training and test sets, patients with one point had a low probability of having four or more LN+ (3.8% and 3.3%, respectively).
Conclusion
Tumor size, number of positive SLN, and the proportion of positive SLN influence whether patients will have four or more LN+. A simple model can predict the probability of requiring PMRT.