Simple Summary
This study examined the effectiveness of mammography and ultrasound in detecting locoregional recurrence among Asian women with breast cancer who underwent breast-conserving surgery. During 10 years of follow-up, both modalities showed comparable performance in identifying recurrences, although early detection within the first postoperative year was achieved exclusively by ultrasound. These findings suggest that annual mammography remains appropriate for surveillance, while early ultrasound is sufficient during the first year after surgery.
Abstract
Background: Breast cancer requires long-term surveillance, as recurrence and mortality risks extend beyond 10 years. Mammography (MMG) is the standard imaging modality; however, its effectiveness is reduced in Asian women owing to dense breast tissue. The optimal timing of surveillance MMG after breast-conserving surgery remains unclear, particularly the value of routine 6-month MMG. We evaluated the roles of MMG and ultrasound in detecting ipsilateral and contralateral breast cancer recurrence after breast-conserving surgery. Methods: This retrospective study included 961 patients with operable breast cancer who underwent breast-conserving surgery with or without axillary surgery between 2011 and 2015 at Kyungpook National University Chilgok Hospital. Surveillance consisted of biannual imaging for the first 2 years, followed by annual imaging for up to 10 years. Ipsilateral and contralateral breast cancer recurrences were analyzed according to detection modality, including MMG and ultrasound. Multivariate Cox proportional hazards regression analysis was performed to identify independent risk factors for recurrence. Results: During a mean follow-up of 139 months, 56 patients (5.8%) experienced locoregional recurrence, and 41 (4.3%) developed distant metastasis. Among 35 in-breast recurrences, 14 (40.0%) were ipsilateral and 21 (60.0%) contralateral. Ipsilateral recurrences were more often detected via either MMG or ultrasound alone, whereas contralateral cancers were typically detected through both modalities. During the first postoperative year, all ipsilateral and contralateral recurrences were detected exclusively by ultrasound, with no cancers identified by 6-month MMG (95% CI for 6-month detection: 0–0.38%). Multivariate analysis identified positive axillary lymph node status as the only independent predictor of locoregional recurrence (HR 2.52, 95% CI 1.14–5.54, p = 0.022). Detection patterns showed no significant differences across molecular subtypes (p = 0.665). Conclusions: Annual MMG remains appropriate for breast cancer surveillance in accordance with current guidelines. However, MMG at 6 months post-surgery may be unnecessary, as early detection during the first year was achieved solely by ultrasound. The complementary role of MMG and ultrasound is consistent regardless of molecular subtype.