Accuracy of perfusion MRI with high spatial but low temporal resolution to assess invasive breast cancer response to neoadjuvant chemotherapy: a retrospective study

Abstract

Background: To illustrate that Breast-MRI performed in high spatial resolution and low temporal resolution (1 minute) allows the measurement of kinetic parameters that can assess the final pathologic response to neoadjuvant chemotherapy in breast cancer.

Methods: Breast-MRI was performed in 24 women before and after treatment. Eight series of 1.11 minute-duration were acquired with a sub-millimeter spatial resolution. Transfer constant (K(trans)) and leakage space (V(e)) were calculated using measured and theoretical Arterial Input Function (AIF). Changes in kinetic parameters after treatment obtained with both AIFs were compared with final pathologic response graded in non-responder (< 50% therapeutic effect), partial-responder (> 50% therapeutic effect) and complete responder. Accuracies to identify non-responders were compared with receiver operating characteristic curves.

Results: With measured-AIF, changes in kinetic parameters measured after treatment were in agreement with the final pathological response. Changes in V(e) and K(trans) were significantly different between non-(N = 11), partial-(N = 7), and complete (N = 6) responders, (P = 0.0092 and P = 0.0398 respectively). A decrease in V(e) of more than -72% and more than -84% for K(trans) resulted in 73% sensitivity for identifying non-responders (specificity 92% and 77% respectively). A decrease in V(e) of more than -87% helped to identify complete responders (Sensitivity 89%, Specificity 83%). With theoretical-AIF, changes in kinetic parameters had lower accuracy.

Conclusion: There is a good agreement between pathological findings and changes in kinetic parameters obtained with breast-MRI in high spatial and low temporal resolution when measured-AIF is used. Further studies are necessary to confirm whether MRI contrast kinetic parameters can be used earlier as a response predictor to neoadjuvant chemotherapy.

Figure 1

Changes (median, 1^st and 3^rd quartile and range) in leakage space (V_e) after neoadjuvant chemotherapy in complete responders (Sataloff grade A), partial responders (Sataloff grade B) and non-responders (Sataloff grade C+D). Kinetic parameters were obtained with measured AIF. The non-responder patient that had an increase in V_e (+193%) is not shown.

Figure 2

Images show changes in transfer constant (K^trans) in patient 22, complete responder to neoadjuvant chemotherapy (Sataloff A). Columns show in A and D: anatomic subtraction images; in B and E: corresponding K^trans map acquired using measured Arterial Input Function (AIF); and in C and F: corresponding K^trans map acquired using theoretical AIF. Images A, B, and C show data before neoadjuvant chemotherapy treatment and images D, F, and G are post-treatment. After treatment a decrease of -98% is seen in K^trans using measured AIF values and a decrease of -29% using theoretical AIF values. Note the difference between K^trans values before treatment when using measured and theoretical AIFs. To increase visibility of the color encoded K^trans pixels the scale was reduced in postchemotherapy images.

Figure 3

Images show changes in volume leakage (V_e) in patient 10 non responder to neoadjuvant chemotherapy (Sataloff grade C). Columns show in A and D: anatomic subtraction images; in B and E: corresponding V_e map acquired using measured Arterial Input Function (AIF); and in C and F: corresponding V_e map acquired using theoretical AIF. Images A, B, and C show data before neoadjuvant chemotherapy treatment and images D, F, and G are post-treatment. After treatment, low decreases in V_e median were seen using the measured AIF (-59%) and theoretical AIF (-50%) in agreement with the pathological observation. Note the disagreement with tumour size changes (-100%). To increase visibility of the color encoded V_e pixels the scale was reduced in postchemotherapy images.

Figure 4

ROC analysis to differentiate patients' response to neoadjuvant chemotherapy. Using measured AIF a decrease in V_e of less than -72% results in 73% sensitivity for identifying non-responders (specificity 92%; area 0.83). Using theoretical AIF, the cutoff value of -51% had lower accuracy (sensitivity 64%; specificity 100%; area 0.74). For transfer constant using measured AIF, a decrease of less than -84% results in 73% sensitivity in the identification of 8 of 11 non-responders patients (Specificity 77%; area under ROC curve 0.80). Using calculated AIF, the cutoff value of -85% had lower accuracy (sensitivity 46%; specificity 54%; area under ROC curve 0.48).