Contrast enhanced magnetic resonance imaging underestimates residual disease following neoadjuvant docetaxel based chemotherapy for breast cancer

Aims We prospectively compared the ability of magnetic resonance imaging (MRI) to measure residual breast cancer in patients treated with different neoadjuvant chemotherapy regimen. Methods Forty patients with locally advanced breast carcinoma underwent neoadjuvant chemotherapy. Twelve patients received 5-fluoro-uracyl-epirubicin-cyclophosphamide (FEC-group, six cycles), 28 (DXL-group) received docetaxel-based chemotherapy (six cycles DXL-epirubicin: 13 patients, eight cycles DXL alone: 15 patients). All patients had baseline and preoperative MRI. The spread of pathologic residual disease (PRd) was compared to preoperative MRI measures according to chemotherapy regimen. Results MRI over/underestimation of the spread of residual tumour was never superior to 15 mm in FEC group, whereas it appeared in 11/28 (39%, 30–48%—95% CI) patients in DXL group (p=0.017). Tumour shrinkage led to single nodular residual lesions in FEC group, whereas vast numerous microscopic nests were observed in docetaxel group in pathology. Conclusion Among tumours treated with a taxane-containing regimen, residual disease was frequently underestimated by MRI because of PRd features.