The American Society of Clinical Oncology (ASCO) annual conference convenes oncology professionals worldwide to share the latest cancer research and shape cancer care. LBCA has compiled lay summaries of the research abstracts presented at the conference. Additional summaries will be added as they are received.
ASCO 2026 Abstract #636 – Breast Cancer-Specific Mortality in Invasive Lobular Versus Ductal Carcinoma Over 30 Years
Authors: Jose P. Leone, Julieta Leone, Noah Graham, Julian Iturbe, Kristina Fanucci, Rinath Jeselsohn, Guilherme Nader Marta, Carlos T. Vallejo, Nancy U. Lin, Sara M. Tolaney, Meredith M. Regan, Nabihah Tayob, Otto Metzger
Organizations: Dana-Farber Cancer Institute and Harvard Medical School, Boston, Massachusetts, and collaborating institutions
Invasive lobular carcinoma (ILC) is known to behave differently from invasive ductal carcinoma (IDC), including a tendency for recurrences to occur many years after diagnosis. To better understand long-term outcomes, researchers analyzed data from more than 423,000 women with stage I-III breast cancer enrolled in the SEER database between 1990 and 2012. They compared breast cancer-specific mortality, or the risk of dying from breast cancer, among patients with ILC and IDC over a period of up to 30 years.
Researchers found that patients with ILC initially had a lower risk of dying from breast cancer than patients with IDC during the first 5 to 10 years after diagnosis. However, this pattern changed over time. After accounting for differences in tumor characteristics and treatments, the risk of breast cancer-related death gradually increased for patients with ILC and eventually became higher than for patients with IDC. This trend was particularly evident among patients with hormone receptor-positive breast cancer, the subtype most commonly associated with ILC. Even among women who had already survived 10 or 15 years after diagnosis, those with ILC remained at a higher risk of dying from breast cancer than those with IDC.
For patients, these findings reinforce what many in the lobular breast cancer community have long recognized: the risk of recurrence and breast cancer-related death may extend well beyond the first decade after diagnosis. The results highlight the importance of long-term follow-up, survivorship planning, and continued research into strategies that may help reduce the risk of late recurrence in people with ILC.
ASCO 2026 Abstract #587 – Distant Recurrence-Free Survival in Invasive Lobular Carcinoma (ILC) with Isolated Tumor Cells: Does pN0(i+) Behave Like Node-Negative or Node-Positive Disease?
Authors: Jason A. Mouabbi, Akshara Singareeka Raghavendra, Taiwo Adesoye, Sarah Pasyar, Roland L. Bassett Jr., Rita A. Mukhtar, Vicente Valero, Amy A. Hassan, Azadeh Nasrazadani, Bora Lim, Richard A. Ehlers Jr., Cristina Checka, Rachel M. Layman, Mariana Chavez Mac Gregor, Sharon H. Giordano, Jennifer K. Litton, Funda Meric-Bernstam, Henry M. Kuerer
Organization: The University of Texas MD Anderson Cancer Center, Houston, Texas
When breast cancer spreads to the lymph nodes, the amount of cancer found can influence treatment decisions and estimates of recurrence risk. However, it has been unclear whether isolated tumor cells (ITCs), tiny clusters of cancer cells found in lymph nodes, carry the same significance in invasive lobular carcinoma (ILC) as larger amounts of lymph node involvement. This study examined whether patients with ILC and ITCs have outcomes more similar to those with node-negative disease or node-positive disease.
Researchers analyzed data from 4,217 patients with ILC treated at MD Anderson Cancer Center. Among them, 169 patients had isolated tumor cells in their lymph nodes. The researchers compared distant recurrence-free survival, a measure of how long patients remained free from cancer spreading to distant parts of the body. They found that patients with isolated tumor cells had outcomes similar to those with node-negative disease and significantly better outcomes than patients with node-positive disease. Even after accounting for factors such as age, tumor characteristics, and treatments received, isolated tumor cells were not associated with a higher risk of distant recurrence.
For patients, these findings are reassuring and suggest that the presence of isolated tumor cells alone may not indicate a higher risk of distant recurrence in ILC. If confirmed in future studies, these results could help doctors avoid overtreatment and support more personalized treatment decisions for patients whose lymph nodes contain only very small amounts of cancer.
ASCO 2026 Abstract #540 – Adjuvant Chemotherapy Benefit in Invasive Lobular Carcinoma (ILC) by Oncotype DX Recurrence Score and Menopausal Status
Authors: Arya Mariam Roy, Yevgeniya Gokun, Brandon Slover, Nerea Lopetegui-Lia, Dionisia M. Quiroga, Kai C. Johnson, Gilbert Bader, Ashley P. Davenport, Sagar D. Sardesai, Robert Wesolowski, Sara Myers, Erin E. Burke, Annapurna Gupta, Sarmila Majumder, Margaret E. Gatti-Mays, Nicole O. Williams, Daniel G. Stover
Organization: The Ohio State University Comprehensive Cancer Center – James Cancer Hospital, Columbus, Ohio
The Oncotype DX Recurrence Score is commonly used to help determine whether people with early-stage hormone receptor-positive (HR+), HER2-negative breast cancer may benefit from chemotherapy after surgery. However, most of the evidence supporting its use comes from studies that included relatively few patients with invasive lobular carcinoma (ILC). This study examined whether the Recurrence Score predicts chemotherapy benefit in patients with ILC and whether results differ based on menopausal status.
Researchers analyzed data from nearly 142,000 patients with early-stage HR+/HER2-negative ILC in the National Cancer Database. They found that chemotherapy was associated with improved overall survival primarily among patients with high Recurrence Scores. This benefit was most apparent in postmenopausal patients, where chemotherapy was linked to higher survival rates at 10 years. In contrast, patients with low Recurrence Scores did not appear to benefit from chemotherapy. Among premenopausal patients, chemotherapy benefit was observed only in those with intermediate Recurrence Scores, while no clear benefit was seen in patients with low or high scores.
For patients, these findings suggest that chemotherapy decisions in ILC should be individualized and guided by both tumor biology and menopausal status. The results support avoiding chemotherapy in many patients with low Recurrence Scores while identifying a subgroup of patients with high-risk disease who may benefit. They also highlight ongoing questions about how well the Oncotype DX test predicts chemotherapy benefit specifically for people with lobular breast cancer, particularly those who are premenopausal.
ASCO 2026 Abstract #641 – Impact of Social Marginalization on Stage at Presentation and Survival for Invasive Lobular Versus Ductal Breast Carcinoma
Authors: David W. Lim, Kelly A. Metcalfe, Vasily Giannakeas, Steven A. Narod
Organizations: Women’s College Hospital and University of Toronto, Toronto, Ontario, Canada
Social and economic factors can influence when breast cancer is diagnosed, how advanced it is at diagnosis, the treatments received, and how well patients do after diagnosis. This study examined whether measures of social marginalization, such as living alone, limited financial resources, lower workforce participation, and housing-related factors, were associated with stage at diagnosis and survival among patients with invasive lobular carcinoma (ILC) and invasive ductal carcinoma (IDC) in Ontario, Canada.
Researchers analyzed data from more than 180,000 breast cancer cases diagnosed between 2005 and 2025, including over 23,000 cases of pure or mixed lobular breast cancer. They found that patients living in areas with greater social and economic disadvantage were less likely to have received recent mammograms and were more likely to be diagnosed with more advanced-stage disease. These same factors were also associated with a higher risk of death after a breast cancer diagnosis. In addition, patients with pure ILC had a modestly higher risk of death compared with patients with IDC. The associations between social marginalization and worse outcomes remained significant even after accounting for tumor characteristics and treatments received.
For patients, these findings highlight that factors beyond the biology of the tumor can influence breast cancer outcomes. Access to screening, social support, economic resources, and other community-level factors may affect how early breast cancer is detected and how well patients do over time. The study underscores the importance of reducing barriers to screening and care while ensuring that all patients have access to the support and resources they need throughout their cancer journey.
ASCO 2026 Abstract #531 – Chemotherapy (CT) Use by Oncotype DX Recurrence Score (RS) in Hormone Receptor-Positive, HER2-Negative (HR+/HER2-) Invasive Lobular Carcinoma (ILC): A Contemporary National Cancer Database (NCDB) Analysis
Authors: Marija Sullivan, Xiudong Lei, Inimfon Jackson, Jason A. Mouabbi, Mariana Chavez Mac Gregor
Organizations: Duke University School of Medicine, Durham, North Carolina, and The University of Texas MD Anderson Cancer Center, Houston, Texas
The Oncotype DX Recurrence Score is commonly used to help determine whether chemotherapy may benefit patients with early-stage hormone receptor-positive, HER2-negative breast cancer. However, most studies validating this test included relatively few patients with invasive lobular carcinoma (ILC), leaving uncertainty about how well it guides treatment decisions in this subtype. This study examined how Oncotype DX scores influence chemotherapy use in real-world practice and whether chemotherapy improves survival for patients with ILC.
Researchers analyzed data from more than 30,000 patients with early-stage HR-positive, HER2-negative ILC. Most patients had low or intermediate Recurrence Scores, while only 7% had high scores. Chemotherapy use closely followed Oncotype DX results: only a small percentage of patients with low or intermediate scores received chemotherapy, compared with two-thirds of patients with high scores. The researchers found that chemotherapy was associated with improved overall survival only in patients with high Recurrence Scores. No survival benefit was observed among patients with low or intermediate scores. Despite this finding, approximately one-third of patients with high Recurrence Scores did not receive chemotherapy.
For patients, these results provide additional evidence that the Oncotype DX test can help guide chemotherapy decisions in lobular breast cancer. The findings suggest that patients with low or intermediate Recurrence Scores may be able to avoid chemotherapy without compromising survival, while those with high scores may benefit from treatment. The study also highlights an opportunity to better understand why some high-risk patients do not receive chemotherapy and whether additional support or education could improve treatment decision-making.
ASCO 2026 Abstract #1141 – Clinical Impact and Temporal Evolution of Mutational Signatures in Metastatic Lobular Breast Cancer
Authors: Sherry Shen, Fresia Pareja, Lounes Djerroudi, Xin Pei, Charlie White, Yuan Chen, Jane Chen, Anton Safonov, Pedram Razavi, Chau T. Dang, Komal L. Jhaveri
Organizations: Memorial Sloan Kettering Cancer Center, New York, New York; Weill Cornell Medicine, New York, New York; Institut Curie, Paris, France
Metastatic invasive lobular carcinoma (ILC) has unique genetic features, but researchers are still working to understand the biological processes that drive tumor growth and influence outcomes over time. In this study, investigators analyzed tumor sequencing data from more than 650 patients with metastatic ILC to identify patterns of DNA changes, known as mutational signatures, and determine whether these patterns were associated with survival.
Researchers found that the two most common mutational signatures were APOBEC, a process that causes DNA mutations, and a clock-like or aging signature associated with the natural accumulation of mutations over time. Patients whose tumors were dominated by the APOBEC signature had shorter overall survival than those whose tumors were dominated by the aging signature. The researchers also examined patients who had tumor samples collected at multiple time points during metastatic disease. Over time, APOBEC became more common as the dominant mutational signature, while the aging signature became less common, suggesting that the biology of metastatic ILC can evolve as the disease progresses.
For patients, these findings provide new insights into the biology of metastatic lobular breast cancer and may help explain why some tumors behave more aggressively than others. The results suggest that mutational signatures could eventually be used to better predict outcomes, monitor how tumors change over time, and identify patients who may benefit from specific targeted treatment approaches. Additional research will be needed to determine how these findings can be incorporated into clinical care.
ASCO 2026 Abstract #564 – Distinct Late Recurrence Patterns and Immune Landscape of HER2-Positive Invasive Lobular Carcinoma (ILC): Analysis of NCCTG N9831 (Alliance) Trial and Real-World Cohort
Authors: Thiti Susiriwatananont, Sachin Kumar Deshmukh, Panuch Eiamprapaporn, Zhuo Li, Sharon Wu, Keith L. Knutson, Aziza Nassar, Yi Liu, Edith A. Perez, Dario Trapani, Maryam B. Lustberg, George W. Sledge Jr., E. A. Thompson, Saranya Chumsri
Organizations: Mayo Clinic Florida, Dana-Farber Cancer Institute, Yale Cancer Center, Caris Life Sciences, and collaborating institutions
HER2-positive invasive lobular carcinoma (HER2+ ILC) is a rare subtype of breast cancer, representing only about 5% of all ILC cases. Because it is uncommon, relatively little is known about its long-term outcomes or whether it behaves differently from HER2-positive invasive ductal carcinoma (IDC). In this study, researchers analyzed data from a large clinical trial and a real-world patient cohort to better understand recurrence patterns and the biology of HER2+ ILC.
The researchers found that patients with HER2+ ILC benefited from trastuzumab (Herceptin)-based therapy to a similar degree as patients with HER2+ IDC during the first several years after diagnosis. However, important differences emerged over time. While recurrence-free survival was similar at the first five years, patients with HER2+ ILC experienced a greater decline in recurrence-free survival between years 5 and 15 compared with patients with IDC. In a separate real-world cohort, patients with HER2+ ILC also tended to have shorter overall survival. The researchers identified several biological differences in HER2+ ILC, including distinct immune cell patterns and lower activity of pathways involved in cell growth and DNA repair.
For patients, these findings suggest that HER2+ lobular breast cancer may carry a higher risk of late recurrence . The results reinforce the importance of long-term follow-up and survivorship planning for people with HER2+ ILC. They also highlight that HER2+ ILC has unique biological features that may eventually help researchers develop more personalized treatment and monitoring strategies for this rare subtype.
ASCO 2026 Abstract TPS1166 – IvoLoC: A Phase II Trial of Ivonescimab (IVO) in Endocrine-Refractory Hormone Receptor-Positive (HR+) or Triple-Negative (TN) Metastatic Invasive Lobular Carcinoma (mILC)
Authors: Jason A. Mouabbi, Paula R. Pohlmann, Rachel M. Layman, Roland L. Bassett Jr., Lavinia P. Middleton, Bora Lim, Toni Zaayman, Krystle Nomie, Evgeny Barykin, Anastasiya Evdokimova, Mariana Chavez Mac Gregor, Jennifer K. Litton, Sharon H. Giordano, Funda Meric-Bernstam
Organizations: The University of Texas MD Anderson Cancer Center, Houston, Texas; Summit Therapeutics; BostonGene
Metastatic invasive lobular carcinoma (mILC) can be challenging to treat once hormone therapies stop working. Patients with endocrine-resistant HR-positive or triple-negative mILC often have limited treatment options and may experience disease progression within a few months of standard therapies. Researchers have identified unique biological features in lobular breast cancer, including differences in the immune system and blood vessel growth within tumors, which may create opportunities for new treatment approaches.
This abstract describes the design of the IvoLoC clinical trial, a phase II study evaluating ivonescimab, an investigational drug that targets both the PD-1 immune checkpoint pathway and VEGF, a protein involved in blood vessel formation. By simultaneously stimulating the immune system and blocking tumor blood supply, researchers hope to improve outcomes for patients with metastatic lobular breast cancer. The trial is enrolling patients with HR-positive/HER2-negative mILC whose disease has progressed despite prior endocrine therapies, as well as patients with triple-negative mILC. Participants receive ivonescimab intravenously every three weeks and are monitored with regular imaging scans.
For patients, this study is significant because it represents one of the few clinical trials developed specifically for metastatic lobular breast cancer. While no efficacy results are available yet, the trial reflects growing recognition that mILC has distinct biology that may require different treatment strategies. Researchers also plan to study blood-based biomarkers and tumor characteristics that could help identify which patients are most likely to benefit from this approach.
ASCO 2026 Abstract #1079 – Outcomes by Lobular Histology Status at Initial Diagnosis in Patients in the INAVO120 Phase 3 Trial with PIK3CA-Mutated, Hormone Receptor-Positive, HER2-Negative, Endocrine-Resistant Advanced Breast Cancer Treated with Inavolisib + Palbociclib + Fulvestrant
Authors: Nicholas C. Turner, Kevin Kalinsky, Katherine E. Hutchinson, Yanling Jin, Tiffany D. Clark, Komal L. Jhaveri, Sibylle Loibl, Cristina Saura Manich, Christine Desmedt, Hans Wildiers, Seock-Ah Im, Patrick Neven, Peter Schmid, Dejan Juric, Sherene Loi, Stephanie Hilz, Thomas J. Stout
Organizations: Royal Marsden Hospital and Institute of Cancer Research, London, United Kingdom; Genentech/Roche; Memorial Sloan Kettering Cancer Center; and collaborating institutions
Patients with hormone receptor-positive, HER2-negative metastatic breast cancer that has stopped responding to endocrine therapy often face limited treatment options. The INAVO120 clinical trial previously showed that adding inavolisib, a targeted therapy that blocks the PI3K pathway, to palbociclib and fulvestrant improved outcomes for patients whose tumors carried a PIK3CA mutation. This analysis examined whether patients with invasive lobular carcinoma (ILC) benefited from treatment to the same extent as patients with other breast cancer subtypes.
Researchers evaluated outcomes among patients with lobular breast cancer, including both pure lobular and mixed lobular tumors. They found that treatment with inavolisib plus palbociclib and fulvestrant improved outcomes compared with palbociclib and fulvestrant alone, regardless of lobular histology status. The benefit was seen in patients with both pure and mixed lobular tumors and was observed whether or not tumors carried alterations in the CDH1 gene, a common feature of lobular breast cancer. The distribution of PIK3CA mutations was similar across histologic subtypes, suggesting that patients with lobular breast cancer can benefit from this targeted treatment approach when their tumors harbor a PIK3CA mutation.
For patients, these findings are encouraging because they demonstrate that the benefits of inavolisib extend to people with lobular breast cancer, a group that is often underrepresented in clinical trials. The results support the use of inavolisib, together with palbociclib and fulvestrant, as a treatment option for patients with PIK3CA-mutated, hormone receptor-positive, HER2-negative metastatic lobular breast cancer whose disease has become resistant to endocrine therapy.