Abstract PS5-10-20: Invasive lobular breast cancer and surveillance: A patient experience survey study

Abstract Background: The Lobular Breast Cancer Alliance (LBCA) is a nonprofit patient advocacy group committed to raising awareness and promoting research on invasive lobular carcinoma (ILC), which is 15% of breast cancers and understudied. The hallmark of ILC, lack of E Cadherin, causes non-cohesive tumor growth. Consequently, imaging studies are less accurate for diagnosis, staging and monitoring for recurrence or progression. Patients’ concern about efficacy of surveillance was the impetus for this study. Methods: LBCA conducted an anonymous online survey in 12/2024 of respondents (RSPs) with ILC who had completed local disease treatment and RSPs living with metastatic ILC (mILC), distributed via LBCA’s newsletter, social media, and partners. The survey addressed surveillance and included a 10-point scaled question about fear of cancer recurrence or progression (FCR) (10 being high). Results: 1706 RSPs had ILC or ILC mixed type. 70% of RSPs were from the US, 11% UK, 6% Australia, 5% Canada, and 8% from 26 other countries. Mean age at diagnosis was 60. 88% of RSPs had had early (stage I-III) breast cancer (EBC) and 12% were living with mILC. 70% of RSPs had dense breasts. 44% of US-based RSPs and 13% of non-US RSPs reported having no breast imaging surveillance because they had double mastectomies. For those with EBC ILC having regular breast imaging, the most common surveillance plans included mammogram (US-based RSPs 92% vs. non-US-RSPs-87%), ultrasound (US-26% vs. non-US-38%), breast MRI (US-50% vs. non-US-26%), and contrast enhanced mammogram (CEM) (US-9% vs. non-US-7%). Surveillance including MRI and CEM was significantly (p = .05) associated with high confidence compared to no confidence. Of 37 (3% of 1496) EBC RSPs who indicated they had a local recurrence, only 28% indicated that their routine imaging test initially detected the recurrence. For those with mILC, the most common surveillance modalities included regular CT scans, bone scans, MRIs, FDG PETs, FES PETs, regular CBC, CMP, tumor marker, and some form of liquid biopsy. The reported use of FDG PET, FES PET, CMP and liquid biopsies were higher in US RSPs compared to non-US RSPs. Notably, 81% of EBC RSPs with high FCRs (8-10) were not sure or had no confidence their surveillance plan would detect recurrence, and 49% of RSPs with mLC with high FCRs lacked confidence their plan would detect a progression. Conclusions: Many women with ILC surveyed worldwide, reported high rates of fear of cancer recurrence/ progression, which is correlated with lack of confidence in surveillance plans. These findings align with our prior work showing low confidence in imaging ILC among breast imagers (Coffey, et al., Journal of Breast Imaging, 2024). More research is needed to identify most effective surveillance for ILC recurrence and progression. Citation Format: M. Mitchell-Daniels, J. H. Axelrod, T. Cushing, L. Hutcheson, M. Jochelson, G. H. Joergensen, T. Langdon, J. A. Mouabbi, R. Mukhtar, B. F. Neilsen, S. Paluch-Shimon, L. Petitti, D. Romer. Invasive lobular breast cancer and surveillance: A patient experience survey study abstract. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS5-10-20.