Which breast cancer phenotypes have the greatest influence on MRI?

Breast cancer phenotype can influence MRI’s ability to evaluate the effectiveness of chemotherapy, according to a study published Oct. 4 in the European Journal of Radiology. But which specific tumor subtypes have the greatest impact on the modality’s performance?

“Achievement of pathologic complete response (pCR) after (neoadjuvant chemotherapy ) NAC is associated with better prognosis in breast cancer patients, especially when more aggressive subtypes are present,” wrote Erika M. S. Negrão, with Hospital de Câncer de Barretos in Brazil, and colleagues. “Breast MRI can accurately assess treatment response after NAC in most cases, however it is important to know when MRI may be less accurate.”

Current knowledge of such information is lacking, the researchers added. The goal of their study, therefore, was to analyze factors that could influence the performance of MRI in detecting pCR after NAC.

Negrão and colleagues retrospectively included 219 patients (mean age of 48 years) with invasive breast carcinoma who underwent breast MRI before and after NAC in their study. Molecular subtypes included were: Luminal B/Her-2 negative (40% of patients), triple-negative (32%), Luminal B/Her-2 positive (20%), and Her-2 overexpression (8%).

MRI diagnosed pCR with 80% accuracy, 69% sensitivity, 87% specificity, positive predictive value of 78% and negative predictive value of 82%. The presence of non-mass enhancement at pretreatment was the sole factor statistically associated with a higher “discordance rate” between MRI and pathologic response. MRI was more sensitive for Her-2 overexpressed and triple-negative subtypes.

“Consistent with the results of a previous study, the current findings demonstrate that MRI sensitivity in identifying pCR was lower in cases involving luminal subtypes,” the researchers wrote. “Furthermore, tumor phenotype at pre-treatment MRI was found to be related to post-treatment MRI accuracy.”

The researchers acknowledged the retrospective design may have been a limitation of their study. They also did not examine background parenchymal enhancement and menopausal status—both factors that could impact MRI’s accuracy.

Going forward, Negrão et al. suggested multicenter studies with more cases will be needed to confirm their findings.