Post-mastectomy surveillance: A patient-reported survey of 110 women with Li-Fraumeni syndrome.

10614 Background: Li-Fraumeni syndrome (LFS) is a highly penetrant autosomal dominant hereditary disorder associated with young onset breast cancer (BC). Therapeutic mastectomy is preferred to enable avoidance of radiation at BC diagnosis (dx), and bilateral mastectomy (BM) for risk reduction as a preventive strategy. After a BM, current guidelines do not recommend post-mastectomy breast screening beyond clinical breast examination (CBE) for LFS carriers. During a patient-focused discussion at the 6 th Li-Fraumeni Syndrome Association (LFSA) Symposium in 2022, women expressed concern about not being offered imaging after the surgery. We therefore conducted a survey study to investigate BC screening practices and new breast events following BM in women with LFS. Methods: Recruitment was performed through electronic invitation sent to members of the LFSA. Respondents 18 years or older who self-identified as having an LFS dx and a personal history of BM, were invited to answer a survey about their cancer history, breast screening, breast surgery and breast events after mastectomy. Post-BM BC event was defined as the first BC event after BM. Questionnaires were administered from August 13 th to September 3 rd , 2024. Bivariate associations between BC history and clinical characteristics were assessed using Fisher’s exact test for nominal categorical variables and two-sample Wilcoxon tests for continuous variables. Results: Among 148 respondents, 110 were eligible; 30 (27.3%) had BM for risk reduction and 80 (72.7%) for BC treatment (60 unilateral BC and 20 for bilateral BC). Median age at first mastectomy was 35.5 years (IQR 28.2,43.0). Most patients (n=82; 74.5%) underwent breast reconstruction with implants only. Periodic CBE performed by a health provider was reported by 70 respondents (63.6%). Patients with BC prior to mastectomies received more clinical surveillance (71.2% vs 43.3%, p<0.01). Follow-up imaging with any modality in regular intervals was reported by 52 respondents (47.3%), and there were no differences between groups regarding BC history and imaging modalities used for surveillance. At a median follow-up of 6 years (IQR 3.0-9.8), a total of 10 post-BM BC events (10/110, 9%) were reported, 50% were identified due to symptoms. Among patients who were receiving imaging surveillance (n=52), only 1 BC event was identified through breast MRI screening. was not significantly associated with a new BC event after BM (p=0.28). All BC events in patients with a BC prior to mastectomies were in the ipsilateral breast of the first BC. Patients with a prior BC had a longer follow-up (7.0 vs 3.0 years, p=0.003). Conclusions: Breast cancer events after mastectomies in this cohort were identified by symptoms rather than surveillance. Further studies are needed to distinguish these subsequent BC events as recurrences or new primaries, and to confirm the clinical value of breast imaging in this setting.