Clinical value of mammography, ultrasound and MR Imaging during the first year after breast conserving therapy of breast cancer

Purpose: To compare the accuracy of lesion detection and characterization and to determine the agreement of observers, methods and timing of mammography (MX), ultrasound (US) and MR imaging (MRI) during the first year after breast conserving therapy. Materials and Methods: The study included 20 patients diagnosed with breast cancer of stages equal or inferior to T2 N1 bi MO after breast conserving therapy and subsequent radiotherapy. Patients with any history of breast diseases in the affected or contralateral breast were excluded. Patients were examined before and at 3, 6 and 12 months after adjuvant radiotherapy with MX, US and dynamic MR mammography. Additional US and MRI were performed 3 months after radiotherapy. All 220 examinations were retrospectively read in a randomized order by two independent readers, blinded for the results of the other examinations. The outcome after 2.5 years of follow-up was used as gold standard. Histological examination was available in one case. Lesion detection and specificity were assessed including kappa values for different reliabilities between observers, timing and methods. The kappa values were used to characterize the degree of agreement as follows: > 0.8 very good; 0.6 - 0.8 good; 0.4 - 0.6 fair; 0.2 - 0.4 minimal; and < 0.2 negligible. Results: Based on the interpretation of all available findings (clinical examination, MX, US, MRT and histology in one case), 20 patients observed for a mean period of 2.5 years had no evidence of intramammary recurrence. Therefore the sensitivity of the various methods could not be assessed. The reading of certainly no lesion was given by MRI in 43%, by MX in 30% and by US in 5% of all examinations (p < 0.05). True negative findings were observed by MRI in 94.4%, by MX in 90.4% and by US in 82.5%. Reliability between observers, timing and imaging methods was 0.496, 0.411, and 0.215 for lesion detection and 0.303, 0.282, and 0.030 for lesion characterization. Conclusion: Within the first year after breast conserving therapy, MRI was the most confident method for the exclusion of lesions and presented the highest true negative rate. The assessment of dignity of a particular lesion was difficult by all imaging methods, reflected by the weak agreement between observers, methods and timing. The difference between times of readings were marginal in the first year after therapy. Agreement between the different diagnostics methods was minimal to negligible.