|The following article is part of conference coverage from the 17th St. Gallen International Breast Cancer Symposium, which is being held virtually from March 7-21, 2021. The team at Cancer Therapy Advisor will be reporting on the latest research conducted by leading experts in breast cancer. Check back for more from the 17th St. Gallen International Breast Cancer Symposium.|
Magnetic resonance imaging (MRI) was found to provide the most concordant tumor size assessment among breast imaging techniques, although significant overestimation exists, according to research presented at the 17th St. Gallen International Breast Cancer Conference 2021.
F.C. Pop, from the Jules Bordet Institute, Université Libre de Bruxelles, in Brussels, Belgium, and colleagues included 752 patients (mean age, 61.8 years; range, 26.9-89.5) who had undergone primary surgery for unifocal invasive breast cancer. Participants also had complete documentation of the tumor size obtained via mammography, ultrasonography, and MRI.
The researchers aimed to evaluate which preoperative breast imaging technique could more accurately determine tumor size in early breast cancer for different intrinsic tumor subtypes by comparing concordance, underestimation, and overestimation with use of the chi-square test.
The study authors analyzed 757 breast cancer tumors: 419 (55.4%) luminal A, 262 (34.6%) luminal B, 56 (7.4%) triple negative, and 20 (2.6%) HER2 enriched. The mean (SD) tumor size was 15.2 (8.3) mm, and the size varied by imaging method: 13.7 (7.3) mm for mammography, 13.1 (7.4) mm for ultrasound, and 16.4 (9.1) mm for MRI.
The concordance between breast imaging technique and final pathology was 56.4% for MRI, 51.7% for ultrasound, and 48.2% for mammography. Mammography and ultrasound underestimated and MRI overestimated the actual tumor size.
The concordance for luminal A tumors was 59.4% by MRI, 57.5% by ultrasound, and 51.8 by mammography (P = .01). Luminal B tumors had a concordance between breast imaging technique and tumor size in 55% of tumors by MRI, 45.8% by ultrasound, and 43.9 by MMG (P =.02).
Concordance in triple-negative breast cancer tumors for MRI and mammography was 41.1%, and it was higher in HER2-enriched tumors for MRI (55%). No statistically significant differences were observed when comparing the different techniques in these 2 intrinsic breast cancer subtypes (P =.68 and P =.85, respectively).
Multivariate analyses demonstrated that tumor size less than 20 mm influenced the concordance for all breast imaging techniques and grade 1 tumors for mammography (P =.007) and MRI (P =.026). Also, invasive ductal carcinoma (P =.013) influenced the concordance for mammography, and progesterone-positive tumors (P =.046), luminal-like tumors (P =.002), and body mass index <25 (P =.013) influenced the concordance for MRI.
“MRI provides the most concordant tumor size assessment among [breast imaging techniques], but a significant overestimation exists,” the study authors concluded. “MRI examination improved the concordance for tumor size measurement in luminal-like tumors and should be preferred especially in luminal B tumors.”
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Pop FC, Stanciu-Pop C, Drisis S, et al. The assessment of primary breast cancer tumor size by magnetic resonance imaging, ultrasonography and mammography: a comparative study across intrinsic tumor subtype. Poster presentation at: 17th St. Gallen International Breast Cancer Conference 2021; March 17-20, 2021. Abstract P133.