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 15mm 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.