The Microbiome and Immuno-oncology in the Spotlight at ASCO 2025

At this year’s meeting of the American Society of Clinical Oncology (ASCO) the pre-eminent cancer research society globally, representatives of the Seerave network are showcasing the latest findings on the role of the microbiome in shaping patient outcomes in immune oncology.

A highlight of this year’s program is the education session and accompanying education book, “Gut Microbiota in Immuno-Oncology: A Practical Guide for Medical Oncologists With a Focus on Antibiotics Stewardship.” Led by Seerave grantees Dr. Arielle Elkrief of CHUM, Prof. Jen McQuade of MD Anderson, and Prof. Laurence Zitvogel of IGR, this session addresses the critical role of gut microbiota as a determinant of immune checkpoint inhibitor (ICI) efficacy, resistance, and toxicity.

Recent large-scale meta-analyses and multi-variate analysis demonstrate that antibiotic use before or during ICI therapy is associated with poorer survival outcomes across several tumor types. This underlines the clinical imperative for antibiotic stewardship in oncology practice.

The presentation will examine the evidence identifying specific gut microbial signatures associated with treatment response, while highlighting dysbiosis from chronic inflammatory processes or comedications as a major risk factor for ICI resistance. Diagnostic approaches, including TOPOSCORE and serum-based biomarkers, will be discussed for dysbiosis identification.

The session will also present an outlook toward potential translational microbiota-centered interventions under investigation for treating gut dysbiosis and optimizing ICI responses.

Early-phase clinical trials of fecal microbiota transplantation from ICI responders or healthy donors have demonstrated safety and preliminary efficacy in addressing primary and secondary resistance across melanoma, non-small cell lung cancer, and renal cell carcinoma. Additional interventions include live bacterial products and dietary modifications such as high-fiber diets showing potential for enhancing ICI activity.

Comprehensive background material is available in the ASCO Educational Book, which was co-authored by the panelists as well as Dr. Bertrand Routy at CHUM, Dr. Lisa Derosa of IGR, and Dr. Laura Bolte of Seerave and UMCG.

Following the educational session, Seerave and the Weston Foundation will co-host a networking event for healthcare professionals and clinical researchers focused on the intersection of gut microbiota, immune function, and oncology. Register to join us at: microbiomecancermeetup.eventbrite.com.

Beyond ASCO: Working to Translate Evidence into Practical Advice for Clinicians

Seerave sees an urgent need to translate emerging findings from this research into practicable takeaways and new tools for oncologists and other medical professionals who work with cancer patients. Seerave has selected Arielle Elkrief and Prof. Jennifer Wargo of MD Anderson to lead a new initiative, the Microbiome x Cancer Working Group – a multi-disciplinary group of experts who will review current evidence on the microbiome and cancer outcomes and issue consensus-based advice for clinicians.

Seerave is also preparing to launch the Seerave Global Oncobiome Atlas– an initiative to unite world-leading clinical research institutions in a consortium dedicated to understanding the impact of microbiome modifiers (including antibiotics) on cancer outcomes.

We welcome collaboration opportunities with the oncology community to advance microbiome research in cancer care.