Patient experiences of diagnosis and treatment of invasive lobular carcinoma: A qualitative study from a prospective registry.

11111 Background: Invasive lobular carcinoma (ILC) is the second most common subtype of breast cancer and comprises 10-15% of all cases. ILC is characterized by a diffuse tumor growth pattern due to the absence of E-cadherin, resulting in diagnostic and management challenges including delays in diagnosis. The impact of these unique features on patients with ILC is unknown. To better understand the patient experience, we conducted a qualitative study using thematic analysis. Methods: 92 patients diagnosed with ILC and treated at a single institution were recruited to a prospective ILC registry from 2023-2025. We collected data primarily through structured patient interviews regarding screening and surveillance methods, locoregional treatment, systemic therapy, and recurrence. Participants were also asked two open-ended questions regarding how they were diagnosed and about their overall experience. The interviews were conducted through 30 to 60-minute phone calls and transcribed verbatim. Inductive coding was used to develop themes. Results: Unique themes were identified corresponding to stages in the diagnosis, treatment, and surveillance of ILC. Participants commonly reported a delay in their diagnosis due to mammographically occult disease and perceived poor sensitivity of breast imaging modalities. This was more pronounced among patients who reported a physical finding related to their breast cancer prior to diagnosis. Additional themes included experiencing a dismissal of symptoms by providers, underestimation of ILC tumor size on pre-operative imaging, and concerns over the impact of dense breasts on imaging sensitivity. At the treatment stage of their patient journey, participants reported that providers did not recognize ILC as a distinct tumor subtype and often recommended mastectomy as the initial surgical approach. After treatment of ILC, participants frequently recounted concerns about how they would identify a recurrence and a desire for improved surveillance methods. Reflecting on their journey, many shared that they wished they had been better informed about breast cancer symptoms and breast self-awareness before their diagnosis. Conclusions: This study highlights the unique challenges and concerns experienced by patients with ILC, emphasizing the need for more tailored imaging strategies, improved awareness among healthcare providers, and enhanced patient education. Selected themes in the patient journey. Patient Journey Stage Unique themes Diagnosis Mammographically occult disease Poor sensitivity of imaging modalities Dismissal of symptoms Underestimation of ILC tumor size Concerns over breast density on imaging sensitivity Treatment Providers not recognizing ILC as a distinct tumor-type Recommending mastectomy Surveillance Concerns about identifying recurrence Desire for improved surveillance methods