Time to development and imaging features of new calcifications in the treated breast after breast-conserving therapy

Objective: The purpose of our study was to analyze the time to development, malignancy rate, location, and mammographic features of new calcifications in the treated breast after breast-conserving therapy (BCT). Materials And Methods: In this HIPAA-complaint, IRB-approved retrospective study, we reviewed the records of patients treated with BCT at our institution with breast-conserving surgery performed between January 1, 2009 and December 31, 2010. A total of 735 breasts in 732 women were included in our study cohort. Factors analyzed included rate of development of new calcifications, malignancy rate of new calcifications, the time between completion of radiation therapy and development of new calcifications, imaging features of new calcifications, and location of the new calcifications in relation to the primary malignancy. Results: During follow-up, new calcifications developed in 155 of the 735 treated breasts (21.1%) and 155 of the 732 women (21.2%). After excluding two cases that were lost to follow-up, the malignancy rate of new calcifications was 5.2% (8/153; 95% CI: 2.3% to 10.0%). The median time to development of the benign calcifications was 27 months (range, 2 to 91 months) and of the malignant calcifications was 41 months (range, 11 to 57 months). Of the 20 (13.1%) cases of new calcifications categorized as BI-RADS 3 (probably benign), all were benign on follow-up (19 cases) or on biopsy (1 case). Of the 51 BI-RADS 4 (suspicious) cases, 8 (16%) were biopsy-proven malignant. The malignancy rate was the highest in fine pleomorphic 100% (1/1), followed by amorphous 17%, (5/29), coarse heterogeneous 8% (2/26) and typically benign 0 (0/97) calcifications (p < 0.0001). The malignancy rate was 1.5% (2/137) for new calcifications within the lumpectomy site vs. 37.5% (6/16) for new calcifications outside the lumpectomy site (p < 0.0001) and was 3.4% (5/147) for new calcifications at or within the same quadrant as the lumpectomy site vs. 50.0% (3/6) for new calcifications in a different quadrant from the lumpectomy site (p=0.002). Conclusion: Most new calcifications that developed in the treated breast after BCT were benign. Evaluation of morphology and distribution of those calcifications is imperative. New calcifications in the treated breast outside the lumpectomy site are more likely to be malignant and should be viewed with greater suspicion. Benign calcifications developed earlier than malignant calcifications, but the time courses overlapped.