Usefulness of postoperative surveillance MR for women after breast-conservation therapy: Focusing on MR features of early and late recurrent breast cancer

PURPOSE: To investigate the imaging characteristics of early and late recurrent breast cancer and the detectability of mammography, ultrasonography, and breast magnetic resonance imaging (MRI) in patients who underwent breast-conservation therapy (BCT). MATERIALS AND METHODS: Total of 1312 women with 2026 surveillance breast MRI after BCT between January 2014 and September 2018 were studied. Early recurrence was defined as newly diagnosed breast cancer and/or axillary metastasis within 12 months of surgery. Late recurrence was defined as recurrence after 12months of surgery. We assessed the detectability of recurrent lesions in each postoperative imaging modality and evaluated characteristics of recurrent lesions on postoperative MRI by comparing early and late recurrence groups. RESULT: Of the 2026 cases, 103 were confirmed as recurrent breast cancer by biopsy or surgery. Thirty-one cases were early recurrence, and 72 cases were late recurrence. MRI showed significantly higher detectability for recurrent lesions (102 cases, 99%) than mammography (59.4%, p < 0.001) or ultrasound (68.9%, p < 0.001), or both mammography and ultrasound (81.6%, p < 0.001). The recurrent lesions did not have typical malignant morphologic features, but variable features on MRI. However, early recurrent lesions showed fast enhancement in early dynamic phase regardless of the kinetic pattern of delayed dynamic phase; and late recurrence lesions showed early fast enhancement and delayed washout pattern. There were 19 cases which were not detected on mammography or ultrasound but could only be detected with MRI. CONCLUSION: Postoperative breast MRI showed significantly higher detectability for recurrent lesions than mammography and ultrasound. Early fast enhancement is the most important feature of recurrent lesions on postoperative breast MRI for both early and late recurrence groups. Due to its high possibility of recurrence, further work-up should be considered regardless of their morphologic features.