Does Diffusion-Weighted MRI After Breast Cancer Affect Prediction Accuracy?

MRI after 12 weeks of therapy predicts complete pathologic response to neoadjuvant chemotherapy.

The timing of diffusion-weighted MR images (DWI-MRI) after starting neoadjuvant chemotherapy for breast cancer may be best indicator for patient response, according to a study published in the journal Radiology.

Researchers from multiple states performed a prospective multicenter study to determine if the change in tumor apparent diffusion coefficient (ADC) at DWI-MRI was predictive of pathologic complete response (pCR) to neoadjuvant chemotherapy for breast cancer.

A total of 272 women with breast cancer were enrolled in the study. They were randomized to treatment with 12 weekly doses of paclitaxel (with or without an experimental agent), followed by 12 weeks of treatment with four cycles of anthracycline. Each woman underwent breast DW-MRI before treatment, at early treatment (three weeks), at midtreatment (12 weeks), and after treatment. The percentage change in tumor ADC from that before treatment (ΔADC) was measured at each time point. Performance for predicting pCR was assessed by using the area under the receiver operating characteristic curve (AUC) for the overall cohort and according to tumor hormone receptor (HR)/human epidermal growth factor receptor 2 (HER2) disease subtype.

The results included 242 patients with evaluable serial imaging data. Their mean age was 48 years ± 10:

• 99 patients had HR-positive (HR+)/HER2-negative (HER2-) disease
• 77 patients had HR-/HER2- disease
• 42 patients had HR+/HER2+ disease
• 24 patients had HR-/HER2+ disease

Eighty (33 percent) of 242 patients experienced pCR. Overall, ΔADC was moderately predictive of pCR at midtreatment/12 weeks and after treatment. Across the four disease subtypes, midtreatment ΔADC was predictive only for HR+/HER2- tumors. In a test subset, a model combining tumor subtype and midtreatment ΔADC improved predictive performance over ΔADC alone.

The researchers concluded that after 12 weeks of therapy, change in breast tumor apparent diffusion coefficient at MRI predicts complete pathologic response to neoadjuvant chemotherapy.