Radiological Underestimation of Tumor Size as a Relevant Risk Factor for Positive Margin Rate in Breast-Conserving Therapy of Pure Ductal Carcinoma In Situ (DCIS)

Simple Summary Negative margins are the most important prognostic factor in breast-conserving therapy (BCT) of ductal carcinoma in situ (DCIS). The impact of radiological underestimation >= 10 mm (defined as mammographic minus histological tumor size in millimeters) has not been further examined. The purpose was to verify the radiological underestimation of DCIS size as a risk factor for positive margins. A pooled analysis of two trials was performed. Inclusion criteria were patients receiving BCT in DCIS. The results show a clinically relevant radiological underestimation in 37% of patients. Radiological underestimation is an independent risk factor for positive margins in BCT of DCIS with microcalcifications. Furthermore, the influencing factors of radiological underestimation were analysed. In multivariate logistic regression, only a mammographic tumor size <= 20 mm was an independent risk factor associated with radiological underestimation. When planning and executing BCT, it has to be considered that a relevant radiological underestimation is significantly higher in mammographic DCIS sizes <= 20 mm. Background: Radiological underestimation of the actual tumor size is a relevant problem in reaching negative margins in ductal carcinoma in situ (DCIS) associated with microcalcifications in breast-conserving therapy (BCT). The aim of this study is to evaluate whether the radiological underestimation of tumor size has an influence on the histopathological margin status. Methods: Patients who underwent BCT with preoperatively diagnosed pure DCIS were included (pooled analysis of two trials). Multiple factors were analysed regarding radiological underestimation >= 10 mm. Radiological underestimation was defined as mammographic minus histological tumor size in mm. Results: Positive margins occurred in 75 of 189 patients. Radiological underestimation >= 10 mm was an independent influencing factor (OR 5.80; 95%CI 2.55-13.17; p < 0.001). A radiological underestimation was seen in 70 patients. The following parameters were statistically significant associated with underestimation: pleomorphic microcalcifications (OR 3.77; 95%CI 1.27-11.18), clustered distribution patterns (OR 4.26; 95%CI 2.25-8.07), and mammographic tumor sizes <= 20 mm (OR 7.47; 95%CI 3.49-15.99). Only a mammographic tumor size <= 20 mm was an independent risk factor (OR 6.49; 95%CI 2.30-18.26; p < 0.001). Grading, estrogen receptor status, and comedo necrosis did not influence the size estimation. Conclusion: Radiological underestimation is an independent risk factor for positive margins in BCT of DCIS associated with microcalcifications predominantly occurring in mammographic small tumors.

Automated summary

The study found that radiological underestimation is an independent risk factor for positive margins in BCT of DCIS associated with microcalcifications. A relevant radiological underestimation was observed in 37% of patients, and mammographic tumor size <= 20 mm was an independent risk factor associated with radiological underestimation.