Combined use of ¹⁸F-FDG PET/CT and MRI for response monitoring of breast cancer during neoadjuvant chemotherapy

To explore the potential complementary value of PET/CT and dynamic contrast-enhanced MRI in predicting pathological response to neoadjuvant chemotherapy (NAC) of breast cancer and the dependency on breast cancer subtype.

We performed (18)F-FDG PET/CT and MRI examinations before and during NAC. The imaging features evaluated on both examinations included baseline and changes in (18)F-FDG maximum standardized uptake value (SUVmax) on PET/CT, and tumour morphology and contrast uptake kinetics on MRI. The outcome measure was a (near) pathological complete response ((near-)pCR) after surgery. Receiver operating characteristic curves with area under the curve (AUC) were used to evaluate the relationships between patient, tumour and imaging characteristics and tumour responses.

Of 93 patients, 43 achieved a (near-)pCR. The responses varied among the different breast cancer subtypes. On univariate analysis the following variables were significantly associated with (near-)pCR: age (p = 0.033), breast cancer subtype (p < 0.001), relative change in SUVmax on PET/CT (p < 0.001) and relative change in largest tumour diameter on MRI (p < 0.001). The AUC for the relative reduction in SUVmax on PET/CT was 0.78 (95% CI 0.68-0.88), and for the relative reduction in tumour diameter at late enhancement on MRI was 0.79 (95% CI 0.70-0.89). The AUC increased to 0.90 (95% CI 0.83-0.96) in the final multivariate model with PET/CT, MRI and breast cancer subtype combined (p = 0.012).

PET/CT and MRI showed comparable value for monitoring response during NAC. Combined use of PET/CT and MRI had complementary potential. Research with more patients is required to further elucidate the dependency on breast cancer subtype.