Ninety-nine patients with confirmed breast cancer were reviewed to identify patients who had two confirmed malignant lesions of identical pathology (Group-1, N=17), and patients who had one malignant lesion and the second benign lesion (Group-2, N=8). Contrast enhancement kinetics from every lesion was measured and analyzed using three different models to obtain fitting parameters related to up-slope, enhancement amplitude, and wash-out, including Model-1: modified Tofts model (v_p, K^trans, k_ep), Model-2: standard Tofts model (K^trans, k_ep), and Model-3: a 3-parameter heuristic model (T_c, A, C). By analyzing lesions from same patients, the differences in whole body hemodynamics thus the blood kinetics could be controlled. Two questions were addressed in this study: i) What is the association between pharmacokinetic parameters analyzed from multiple cancers of identical pathology in same patients?; and ii) What is the difference between secondary malignant lesions and secondary benign lesions with reference to the primary cancer? All three models could fit the enhancement kinetics satisfactorily. Regardless of the analysis model the parameter obtained from the primary cancer and the secondary cancer showed significant correlations. In comparison between Group-1 and Group-2 subjects, the wash-out parameter k_ep in Models-1 and 2 could significantly differentiate benign from malignant lesions, but not the magnitude parameters, K^trans in Model-2 or the parameter A in Model-3. If analyzed using appropriate models the early up-slope parameters, v_p in Model-1 and T_c in Model-3, might be able to distinguish between benign and malignant lesions. When more data are available a reference database can be established with the method described in this study, and from which to determine the likelihood of malignancy for each incidental lesion found in preoperative MRI, with reference to the primary cancer.

Key words: Contrast enhancement kinetics; Differential diagnosis; Multiple breast lesions; Pharmacokinetic model; and Preoperative MRI.