The 2024 Invasive Lobular Carcinoma (ILC) symposium in Leuven, Belgium in September 2024 was fantastic. My 2nd year attending this meeting, which alternates between Europe and the United States, did not disappoint. The meeting brought new ILC insights and to many.

 This meeting focuses just as much on what we don’t know, as what we do know.  Thus, this is a fantastic opportunity to not only obtain current knowledge, but also establish a framework to guide future research. Furthermore, this allows us to face, with greater conviction, the dilemma that is ILC.

The ILC Dilemma

ILC is more challenging to diagnose and treat than invasive ductal carcinoma (IDC) (also termed invasive breast carcinoma of no special type (NST)) due to:

• Subtle Growth Patterns: ILC often grows diffusely, making it harder to detect on mammograms compared to the distinct masses of IDC.

• Delayed Diagnosis: ILC’s diffuse nature often leads to later detection, resulting in larger tumors and higher stages at diagnosis.

• Unclear Surgical Margins: ILC’s growth pattern complicates achieving clear margins during surgery, increasing the likelihood of re-excision.

• Different Metastatic Patterns: ILC metastasizes to unusual locations like the gastrointestinal tract and ovaries, complicating detection and treatment.

• Less Responsive to Chemotherapy: ILC is often less responsive to chemotherapy, limiting treatment options despite being hormone receptor positive.

• Increased Bilateral Cancer Risk: Women with ILC have a higher risk of developing cancer in the opposite breast, necessitating more frequent monitoring or preventive surgeries.

These factors make ILC management more complex and frustrating for patients and healthcare providers.

Second Fiddle

ILC is often overshadowed by IDC in clinical practice and research, leading to:

• Underrepresentation in Research: Most breast cancer research focuses on IDC, resulting in limited data and understanding of ILC.

• Generalized Treatment Approaches: Treatments for ILC are often adapted from IDC guidelines, which may not fully address ILC’s unique characteristics.

• Diagnostic Challenges: Diagnostic tools optimized for IDC can miss ILC, leading to delayed or inaccurate diagnoses.

• Lower Awareness: Public and medical awareness campaigns focus on IDC, leaving ILC patients underserved.

• Suboptimal Outcomes: ILC patients may not receive the most effective treatments due to reliance on IDC-derived protocols, leading to poorer outcomes.

 What I learned from the ILC Symposium:

First, I learned about illness insecurity. This refers to the persistent uncertainty, anxiety, or fear that individuals experience due to the unpredictable nature of their illness. ILC patients often experience illness insecurity due to uncertainty related to diagnostic challenges on imaging as well as unusual patterns of disease spread, treatment paradigms based on IDC rather than ILC, limited ILC research stemming from underrepresentation in clinical trials, surgical challenges often leading to repeat breast surgeries, frustration with providers who have less ILC awareness, and lower public awareness.  The challenges of diagnosing, treating, and monitoring ILC contribute to persistent insecurity and anxiety for patients. This can cause a persistent sense of insecurity, isolation, and anxiety throughout their cancer journey, lowering mood, harming self-care, and increasing psychosocial stress.

The importance of dense breast tissue for early ILC detection is finally being embraced. I say finally because it was only a few years ago, in direct conversation with non-imaging ILC experts, that I was advised that dense breast tissue is not a major issue for ILC. Thankfully, science is unequivocally proving that dense breast tissue, combined with the often-elusive nature of ILC on mammography, makes ILC extremely challenging if not impossible to detect on mammography in far too many cases.

The optimal methods of breast cancer screening continue to be debated, and the opinion on optimal screening strategies is divided, even within the ILC community.

What I heard at the ILC symposium:

 To paraphrase many statements from patient advocates that caught my attention:

 “ILC does not fit within guidelines.  It laughs at them.”

“One-size-fits-all may not work for ILC.”

 “Mammography didn’t find it.  Now I’m being told surveillance will be with mammography.”

 “Too many of us needed to self-advocate to get a diagnosis.”

 “The fear of missed recurrence is different than the fear of recurrence”.

To paraphrase many statements from physicians and researchers that caught my attention:

 “Worse than no screening is a screening program that predictably does not do the job.”

 “The current problem is one of ILC underdiagnosis, not overdiagnosis.”

 “Whole body DWI MRI performed in the academic setting has potential but is underutilized and needs increased acceptance. Commercial free-standing whole body DWI MRI needs to collect and report data on imaging accuracy so we can assess how they are doing.”

 “RECIST 1.1 requirements for measurable disease excludes many ILC patients from clinical trials.”

My specific convictions following the ILC symposium:

1.        ILC experts need to establish response assessment categories for clinical trials for breast cancer. Experts studying and treating other cancer types have developed response assessment criteria to address the limitations of RECIST 1.1, such as Lugano, Prostate Cancer Working Group, IWCLL, IMWG, RANO, and others. The Prostate Cancer Working Group is now working on their fourth iteration of PCWG response criteria!  It's time for the breast cancer community to address this issue collectively, and perhaps the ILC community to address this problem specifically. While a breast cancer or ILC-specific criteria may not be perfect, this could lay the groundwork for future improvements and support the enrollment of ILC patients in clinical trials. 

2.        The ILC community is motivated and resilient.  Despite many real-world challenges ILC patients often face, evidenced by multiple conference sessions that raised more questions than answers, there is hope for many diagnostic and therapeutic advances soon.

3.        Circulating tumor DNA may revolutionize ILC diagnosis and treatment monitoring. MRI and CEM could revolutionize detection of ILC in the screening setting. Theranostics could bring a revolution in ILC treatment.

4.        More money funding needs to be allocated for ILC research!  So many outstanding questions are pleading for answers! Joint advocacy and outreach must continue to expand.

In summary, at the ILC Symposium, ILC takes center stage. Patient advocates, researchers, oncologists, radiologists, pathologists, and surgeons focus exclusively on ILC, inspiring innovation through collaborative discussion to improve outcomes. This dedicated effort ensures that ILC receives the attention it deserves, offering hope and a stronger foundation for future care. The ILC Symposium is not just a gathering; it’s a necessary shift in focus—one that offers hope, drives innovation, and builds a stronger foundation for the future of ILC care.