According to international studies, taking Acetylsalicylic acid daily can protect people with Lynch syndrome from developing colorectal cancer – even at low doses. Researchers from the University Hospital Bonn (UKB), the University of Bonn, and the Center for Integrated Oncology (CIO) Bonn, in collaboration with the self-help organization SemiColon, have now found that these scientific findings have so far been insufficiently incorporated into clinical practice. The results of the LYNX study have now been published as a letter in the journal *The Lancet Gastroenterology & Hepatology*.

People with Lynch syndrome have a significantly increased risk of developing colorectal cancer and other types of cancer due to a hereditary predisposition. The CAPP2 study had already shown in this high-risk group that Acetylsalicylic acid can significantly reduce the long-term risk of colorectal cancer. The study examined a comparatively high daily dose of 600 milligrams. The recently published international CaPP3 study now suggests that even a lower dose of 100 milligrams daily could exhibit a similar cancer-preventive profile, while causing fewer side effects and, in particular, fewer bleeding complications. “Since the statistical criteria for formal equivalence between the two studies were not met in all analyses, the results should still be interpreted with some caution,” says corresponding author Dr. Robert Hüneburg, a senior physician at Medical Clinic I at the UKB, who also conducts research at the University of Bonn. “However, the results of the CaPP3 study suggest that 100 mg daily could be a practical and better-tolerated option for many patients.”

Bonn Survey Conducted Before CaPP3 Publication

The survey of 539 people with Lynch syndrome from across Germany was designed prior to the publication of the CaPP3 results and conducted between December 2025 and February 2026. It therefore reflects the previous use of Acetylsalicylic acid based on the scientific evidence available at that time. “Future studies must show whether the new findings on lower dosages will contribute to Acetylsalicylic acid being used more frequently for cancer prevention,” says Hüneburg.

The Bonn findings reveal a strong awareness of prevention: About 97 percent of respondents are familiar with the specific screening recommendations, and nearly all undergo regular colonoscopies. Nevertheless, only 10.4 percent reported currently taking Acetylsalicylic acid. Only 6.9 percent of the entire group specifically used Acetylsalicylic acid for cancer prevention in Lynch syndrome. “The main reasons cited were a lack of prior engagement with the topic, concerns about side effects, and uncertainty regarding the scientific evidence,” says Dr. Anne-Sophie Layritz, co-first author of the study and a assistant physician at Medical Clinic I at the UKB.

Simultaneously, there was a high level of openness toward new preventive approaches. About three-quarters of those surveyed could, in principle, imagine participating in a study on a preventive mRNA cancer vaccine. After receiving additional information, this proportion rose to about 80 percent. More than 92 percent stated that they would want to receive such a vaccine if it were approved in the future. A majority also accepted the possibility of being assigned to a placebo group and the risk of side effects. “These results show just how great the interest is among those affected in innovative prevention options and in actively participating in research,” says co-first author Nicola Reents of SemiColon.

Implementation Gap in Care

The results of the LYNX study thus do not indicate any fundamental reluctance toward cancer prevention. Rather, there is a significant implementation gap between scientific evidence, medical counseling, and actual application. According to the authors, people with Lynch syndrome are very open to prevention and new research approaches. However, early, understandable, and structured information, as well as an individualized assessment of benefits and risks, are crucial.

Support from the centers of the German Consortium Familial Colorectal Cancer and collaboration with the self-help organization SemiColon were of central importance to the project. Through this network, many affected individuals were reached, and the research questions and results could be contextualized from the patients’ perspective. Nicola Reents of SemiColon is also a co-first author of the publication. “The project is thus a very good example of research that is conducted not just about, but together with, those affected,” emphasizes Hüneburg.

Publication: Anne-Sophie Layritz, Nicola Reents, Katrin van Beekum, Prof. Jacob Nattermann, Robert Hüneburg: The implementation gap in aspirin chemoprevention for Lynch syndrome; The Lancet Gastroenterology & Hepatology, DOI: 10.1016/S2468-1253(26)00216-5