CONTRAST-ENHANCED MRI OF THE BREAST AFTER LIMITED SURGERY AND RADIATION-THERAPY

Objective: Posttherapeutic changes in the breast after tumorectomy (TE ) and radiation therapy (RT) may mimic or obscure recurrent or new mal ignancies and thus interfere with conventional diagnostic studies. We investigated the enhancement of tissue during variable time intervals after therapy with contrast-enhanced MRI in 62 patients. Materials and Methods: We report the results of 77 studies in 62 patients undergoin g TE and RT. We include only those studies with at least 24 months of clinical and mammographic follow-up (n = 60) or histopathologic result s (n = 17).Results: Up to 9 months after therapy, differentiation betw een posttherapeutic changes and recurrence was frequently impossible b ecause of the strong enhancement. Ten to 18 months after therapy, this posttherapeutic enhancement subsided slowly with some interindividual variations. After 18 months posttherapy, no significant enhancement w as encountered in 30 of 32 cases. Diffuse or focal enhancement was pre sent in all recurrent tumors and all recurrences were correctly diagno sed. Furthermore, 4 of 11 recurrences and 10 of 18 single recurrent fo ci were detected by MR alone, based on focal enhancement. Conclusion: Accordingly, contrast-enhanced MR is not recommended during the first 9 months after therapy. Nine to 18 months after therapy, it may be hel pful in those two-thirds of cases where the scar does not enhance. If enhancement takes place (one-third of cases), it may represent either scar or tumor, and in such circumstances, enhanced MR is of no value. After 18 months, enhanced MRI has proven a valuable additional tool. B y correctly detecting or excluding recurrent tumor, it can significant ly improve diagnostic accuracy.