Comparison of whole-body MRI and contrast-enhanced CT for treatment response assessment of mixed visceral- and bone-metastasizing breast cancer.

BackgroundTreatment response assessment can be challenging in bone-metastasizing breast cancer. Whole-body magnetic resonance imaging (WB-MRI) is superior to contrast-enhanced computed tomography (CE-CT) for detecting progressive disease (PD) in bone-only metastatic breast cancer; however, the ability to detect PD in mixed visceral- and bone-metastasizing breast cancer remains to be assessed in prospective studies.PurposeTo prospectively compare WB-MRI and CE-CT for detecting PD in mixed visceral- and bone-metastasizing breast cancer and determine if WB-MRI could detect PD earlier than CE-CT.Material and MethodsA total of 43 women with mixed visceral- and bone-metastasizing breast cancer were prospectively followed with WB-MRI and CE-CT from the initiation of new chemotherapy. Kaplan-Meier analysis of time to progression was performed for both WB-MRI and CE-CT, and the time difference between the two was compared using a one-sample t-test. The ability to detect PD earliest was compared using McNemar's test.ResultsOf the 43 patients enrolled, 21 completed the study. Treatment was changed due to PD in 18 patients and due to side effects in three patients. Median time until change of treatment was 8 months (range=4-21 months). WB-MRI correctly detected PD in 16/18 patients compared to 13/18 for CE-CT. A total of 73 pairs of examinations were analyzed, of which WB-MRI detected PD earliest in 7/18 patients compared to 1/18 for CE-CT (P = 0.035).. There were no statistically significant differences in time to progression between WB-MRI and CE-CT (P = 0.41).ConclusionWB-MRI can detect PD in women with mixed visceral- and bone-metastasizing breast cancer earlier than CE-CT.