Abstract P3-04-04: Correlation of Mammographic Microcalcifications with Final Surgical Pathology after Neoadjuvant Chemotherapy for Breast Cancer

Abstract Introduction: Benefits of neoadjuvant chemotherapy (NAC) in breast cancer include de-escalating surgical management, treating occult systemic metastases and the assessment of in-vivo tumor response. Guidelines for post-NAC imaging to assess response lack specificity on appropriateness and utility of individual imaging modalities for surgical planning. Mammographic microcalcifications are a confounder that are not well studied. We examined the correlation between the mammographic extent of microcalcifications present post-NAC, corresponding MRI lesions, and definitive surgical pathology. Methods: In this retrospective cohort study, patients with calcifications on pre-NAC mammograms were collected from a database of consecutive breast cancer patients receiving NAC at an academic center between January 1st 2014 – December 31st 2019. The primary objective was to determine how the maximum diameter of post-NAC calcifications correlates with final surgical pathology, stratified by tumor receptor subtype. The secondary objectives were to assess correlation of the maximum diameter on final pathology with the maximum diameter of (1) post-NAC mammographic mass (if present) and (2) post-NAC MRI, mass (ME) and non-mass enhancement (NME). Parameters on final surgical pathology included the diameters of invasive disease, ductal carcinoma in-situ (DCIS) and the tumor bed (TB). Pearson’s correlation coefficient was used to evaluate statistical significance and considered strong if R2 ≥70%, moderate if R2 = 25-70% and weak if R2 ≤25%. Results: 343 patients received NAC, of which 157 were excluded for lack of calcifications (n=147), lack of imaging reports (n=8) or inflammatory breast cancer (n=2). 186 patients met the inclusion criteria with a mean age of 49.9 years. 34 (18.3%) patients had triple negative breast cancers (TNBCs). Mammographic calcifications correlated poorly with residual invasive disease (R2= 10.8%), overestimating by 57%. TNBCs demonstrated the strongest correlation between microcalcifications and invasive disease (R2=83%), but calcifications overestimated pathology by 41%. Mammographic calcifications correlated moderately with the TB (R2= 50.3%) and poorly with DCIS (R2 = 3.4%). By subtype, both correlations were strong in TNBCs (R2 = 76.3% and 77.9% respectively). Similarly, focal mass on mammography correlated poorly with pathology except in TNBCs, which correlated moderately with all three pathology parameters (Table 1). In patients with calcifications on mammography, MRI ME and NME correlated weakly with invasive disease, except in TNBCs, where correlation was moderate in ME (R2 = 37.7%) and NME (R2 = 28.4%). Conclusion: In breast cancer patients with microcalcifications, current post-NAC imaging modalities appear to overestimate the extent of residual disease. Surgical excision of all residual microcalcifications may maximize oncologic safety but may also represent over-treatment. Ongoing feasibility trials on surgical omission rely on post-NAC imaging to determine trial candidacy. Our data suggests that potentially eligible patients are excluded on the basis of post-NAC imaging overestimating the extent of residual disease. Further studies are needed to determine the most accurate imaging correlate of residual disease after NAC to plan better surgeries, identify candidates for surgical omission and establish optimal post-NAC imaging guidelines. Current imaging modalities appear most accurate for TNBCs and may be more reliable at identifying exceptional responders for surgical omission in this subtype. Table 1. Summary of Correlation Analyses in Overall and Triple Negative Breast Cancer (TNBC) cohorts. * Average % difference in maximal diameter calculated as (pathology – radiology)/radiology Citation Format: Riordan M. Azam, Nicole Look Hong, David Lim. Correlation of Mammographic Microcalcifications with Final Surgical Pathology after Neoadjuvant Chemotherapy for Breast Cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P3-04-04.

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