Background: The Lobular Breast Cancer Alliance Inc. (LBCA) is committed to raising awareness of the distinctive characteristics of invasive lobular carcinoma (ILC) and promoting and funding ILC research. Comprising 15% of all breast cancers, ILC tumors often form in a linear, sometimes diffuse fashion both within the breast and in metastatic sites, making them difficult to diagnose, monitor, and treat. LBCA surveyed individuals living with metastatic ILC (mILC) about their experiences with detection and monitoring of mILC. Methods: LBCA conducted an anonymous, online survey of persons living with mILC using SurveyMonkey. The survey was shared with LBCA newsletter subscribers, sister organizations, and via social media. Survey questions asked about metastatic site locations, imaging and monitoring modalities, and patient experience with disease progression and clinician discussions about mILC. An independent IRB review determined the study was exempt from full IRB review. Results: 241 people living with mILC completed the survey. 77% were from the US and Canada. 71% were between 35-64 years of age. 41% had been diagnosed with de novo metastatic ILC. Bone was the most common site of initial metastasis with 75% diagnosed de novo (DN) and 59% diagnosed with a distant recurrence (DR). GI metastases (including metastases to stomach, colon, bowel, peritoneum, or rectum) were reported by 11% of the DN and 14% of the DR groups, respectively. Unusual sites for breast cancer metastasis (to genitourinary organs, eye, or skin) were reported by 11% of the DN and 16% of the DR groups. Metastatic progression was reported by 47% of respondents including to bone (42%), to the liver (22%), and 40% reported progression within the initial metastatic site. 36% of individuals with DN mILC reported progression as compared to 54% among those with a DR. Both groups reported living with mILC for similar durations (on average 3.9 years for DN; 3.3 for DR). 36% of respondents reported that at least one imaging modality failed to visualize one or more of their metastatic sites at initial diagnosis of mILC. 54% of respondents with bone metastases and 19% of those with GI metastases indicated their metastases had not been visualized by standard imaging modalities. 48% of all surveyed stated their mILC was an unexpected or an incidental finding made during another medical procedure, of those, 64% were bone metastases. 25% of respondents whose metastases progressed indicated imaging failed to detect one or more of their sites of progression. In both the DN and DR groups, the most frequently utilized tests and/or procedures used to monitor for progression or changes in metastases were routine blood and tumor marker tests. Respondents with DN mILC reported an average 12 months between first report of symptoms and mILC diagnosis. Those with DR reported an average 8 months between symptom reporting and diagnosis. 42% of all respondents reported that a doctor had told them what symptoms to report at any time. 58% of respondents reported feeling that non-oncologists caring for them (primarily PCPs, radiologists, and gastroenterologists) needed to be better informed about ILC. Conclusion: Surveyed individuals confirmed the perception that mILC can occur in unique locations and be difficult to diagnose and that mILC may be challenging to monitor, and standard surveillance methods may fail to visualize mILC. While a large percent of respondents reported that their mILC diagnoses were unexpected or incidental findings during another medical procedure, this may be due to different understandings of “incidental.” This and the fact that more respondents with DR mILC reported progression than those with DN mILC warrant further study.

Citation Format: Laurie B. Hutcheson, Janice Axelrod, Ann Camden, Donna J. Charlevoix, Tracy A. Cushing, Maxine S. Jochelson, Megan L. Kruse, Theresa Langdon, Julia K. Levine, Christine McKay, Otto Metzger, Mason Mitchell-Daniels, Jason Mouabbi, Barbara F. Neilsen. Lobular Breast Cancer Alliance Inc. Survey of Individuals with Metastatic Invasive Lobular Carcinoma [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P6-05-50.