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Abstract Introduction: Breast conserving surgery (BCS) represents the preferred option for surgical treatment for a majority of patients with early-stage breast cancer who are eligible for this approach. When compared with mastectomy approaches, BCS provides patients with equivalent survival while preserving the affected breast. It is necessary to achieve clear surgical margins as positive lumpectomy margins are associated with an increased risk for ipsilateral breast tumor recurrence. With advances in imaging techniques, as well as effective systemic therapy and contemporary radiation therapy, local recurrence after BCS has decreased and overall survival for patients has improved. Retrospective studies have quantified the recurrence rate in unifocal breast cancer as 8 - 15% at 20 years. The NCCN recommends annual mammography at least 6 months after post-lumpectomy radiation therapy, but there is little data regarding more frequent surveillance after lumpectomy in the early post-operative setting. The purpose of this study was to evaluate the impact of short interval surveillance mammography on the detection of early in-breast recurrence in patients undergoing BCS. Methods: Our IRB-approved Breast Cancer Database was queried for patients enrolled from 11/2009 to 6/2023 who underwent breast conservation surgery for a diagnosis of in situ or invasive breast cancer in this retrospective analysis. Per our institutional protocol, patients were recommended to undergo diagnostic mammography of the treated breast(s) every 6 months for 2 years after BCS. After the initial 2 year period, bilateral mammography was performed annually in the absence of other indications. Additional supplemental imaging such as breast ultrasound and MRI were performed at physician discretion and based on patient risk and breast density. Variables of interest included the presence of pathogenic germline mutations, family history of breast cancer, and disease characteristics. Our primary endpoint was ipsilateral breast tumor recurrence. Results: Of 2491 patients who underwent breast conservation surgery for in situ or invasive breast cancer, 191 (7.7%) developed recurrent disease, including ipsilateral and contralateral recurrence, and distant disease, in the study period. A total of 83 (3.2%) patients developed ipsilateral breast recurrence during the entire study period. Of those, 19 (22.9%) were detected within the first two years after surgery. Six of the 19 patients (31.6%) had their recurrences detected on yearly diagnostic mammography while 6 (31.6%) patients had their recurrences detected on interval 6-month unilateral diagnostic imaging. In both groups, 5/6 recurrences were invasive disease after an original diagnosis of invasive cancer, and the remaining patient had recurrent DCIS. The remaining 7/19 patients (36.8%) had their ipsilateral recurrences detected on palpation or other diagnostic imaging. In this group as well, there was one case of recurrent DCIS, with the remaining 6 cases representing recurrent invasive cancer. Of the 19 patients with ipsilateral recurrences, none had pathogenic germline mutations. 4 of the 19 patients (21%) had positive margins after their initial lumpectomy surgery with re- excisions required to achieve clear margins. Conclusion: Interval diagnostic surveillance imaging every 6 months after breast conserving surgery identified almost one-third of the ipsilateral breast tumor recurrences that occurred within the first 2 years after surgery in our population. While our numbers are small, the relationship of re-excision lumpectomy surgery to subsequent risk for local recurrence has been described by others, and bears further study. Particularly in view of our observation that the majority of in-breast recurrences were invasive, our data supports the practice of more frequent imaging follow up in the first 2 years after breast conserving surgery. Citation Format: Pabel Miah, Laura Fiedler, Anthony Baez, Athanasios Sevdalis, Alyssa Marmer, Charles DiMaggio, Linda Pak, Richard Shapiro, Karen Hiotis, Deborah Axelrod, Amber Guth, Freya Schnabel. The Impact of Bi-Annual Diagnostic Imaging on Detecting Ipsilateral Breast Recurrence in Patients Undergoing Breast Conserving Surgery for Breast Cancer abstract. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-23-05.
Miah et al. (Thu,) studied this question.