Objective: Posttherapeutic changes in the breast after tumorectomy (TE) and radiation therapy (RT) may mimic or obscure recurrent or new malignancies 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 undergoing TE and RT. We include only those studies with at least 24 months of clinical and mammographic follow-up (n = 60) or histopathologic results (n = 17).
Results: Up to 9 months after therapy, differentiation between posttherapeutic changes and recurrence was frequently impossible because 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 was encountered in 30 of 32 cases. Diffuse or focal enhancement was present in all recurrent tumors and all recurrences were correctly diagnosed. Furthermore, 4 of 11 recurrences and 10 of 18 single recurrent foci 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 helpful 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. By correctly detecting or excluding recurrent tumor, it can significantly improve diagnostic accuracy.