ICIs therapy is a groundbreaking approach to treating tumors that leverages the immune system to combat malignancies. This approach enhances immune-mediated tumor clearance by blocking negative signals between cancer cells and immune cells (Waldman et al., 2020; Morad et al., 2021). To this end, ICIs that target programmed cell death-1 (PD-1)/programmed death ligand-1 (PD-L1) as well as cytotoxic T lymphocyte-associated protein 4 (CTLA-4) have been developed and employed by researchers in clinical practice (Waldman et al., 2020; Morad et al., 2021). As mounting evidence supports their efficacy and synergistic effects with other cancer treatments, ICIs are increasingly being utilized as a key component in the treatment of many types of cancer, such as melanoma, lung cancer and esophageal cancer (Gadgeel et al., 2020; Rudin et al., 2020; Doki et al., 2022; Livingstone et al., 2022). However, it is important to note that, to date, ICIs remains ineffective for several cancer types, for instance, pancreatic cancer (Bockorny et al., 2022). In some cases, ICIs have not yet attained the status of standard care, as seen in breast cancer (Debien et al., 2023).

However, a notable issue arising from the increasing use of ICIs in clinical practice is their uncontrolled additive impact on the immune system, resulting in irAEs. ICIs manifest unique patterns of toxicity distinct from conventional chemotherapy or other biological agents, often stemming from hyperactive immune reactions against normal organs. irAEs can affect any organ system, including the skin, gastrointestinal tract, cardiovascular system, and endocrine system, among others (Brahmer et al., 2018; Schneider et al., 2021). The frequency of irAEs ranged from 66.4% to 86.8% for all grades, and from 14.1% to 28.6% for grade 3 or higher (Xu et al., 2018). irAEs may be influenced by the patient’s genetic background and microbiome, as well as by treatment-related factors such as combination medication (Jelinic et al., 2018; Cortellini et al., 2020). The mechanism of irAEs is not fully understood but may be related to the overactivation of innate and adaptive immunity caused by the disruption of immune balance by immunotherapy (Pauken et al., 2019). Since the occurrence of irAEs restricts the use of ICIs, it is necessary to further understand the mechanism and influencing factors of irAEs.

Drug-drug interactions (DDI) are a significant focus in the field of systemic anti-cancer treatment. Previous studies have found that combination therapy has an important impact on the outcome of immunotherapy and irAEs. For example, the use of antibiotics and proton pump inhibitors (PPIs) has been associated with poorer outcomes in patients with ICIs (Kostine et al., 2021). Aspirin has become widely used in modern medicine, primarily due to its ability to inhibit the cyclooxygenase (COX) pathway and effectively treat inflammation, pain, and various cardiovascular diseases (Fijałkowski et al., 2022). In recent years, aspirin has also been found to have a well-documented role in the prevention and treatment of tumors (Algra and Rothwell, 2012; Rothwell et al., 2012), especially in colorectal cancer (Rothwell et al., 2010; Drew and Chan, 2021). With the innovation in the field of cancer treatment and the emergence of a new therapy, namely, immunotherapy, researchers have gradually paid attention to the relationship between aspirin and immunotherapy. Recent clinical studies have suggested that the combination of aspirin and ICIs is associated with better outcomes (Cortellini et al., 2020; Zhang et al., 2021). In addition, Aspirin use and its relationship to irAEs were rarely addressed in these studies. Given the widespread acceptance of ICIs into standard practice, it is crucial to gain a better understanding of the association between aspirin treatment and irAEs.

FAERS is a comprehensive drug adverse reaction database maintained by the FDA. Its advantages include broad coverage of adverse events from clinical trials to market use, timely updates, comprehensive drug information, large-scale data for analysis, and reliable reporting from healthcare professionals and consumers. It is a trusted resource for monitoring and reporting drug adverse reactions, and helps to inform better clinical practice and healthcare decision-making. To date, no systematic evaluation of the association of aspirin with irAEs has been published. Therefore, our aim was to determine the association between aspirin use and irAEs in patients receiving immunotherapy by analyzing the data in FAERS. Our research affirms that aspirin users exhibited a higher risk of irAEs when compared to non-aspirin users. Nonetheless, this association displayed variability across distinct cancer types, adverse events, and ICIs.

By understanding how the immune system interacts with tumor cells, scientists have established new therapies for cancer treatment that have brought noteworthy clinical benefits for cancer patients (Morad et al., 2021). However, many cancer patients have underlying diseases, and the presence of other drugs may affect the immunotherapy. ICIs leverage diverse mechanisms and pathways to harness the immune system’s ability to eradicate tumor cells. Consequently, potential interactions between concomitant medications and ICIs transcend the typical assessment of pharmacodynamic and pharmacokinetic interactions between drugs. Aspirin is currently one of the most widely used basic drugs, Previous studies reported that aspirin use is associated with better outcomes with immunotherapy, However, it is not clear whether aspirin use impacts irAEs. This is one of the first studies to analyze the association between aspirin use with irAEs using FEARS data with innovative and comprehensive benefits. Our study showed that aspirin exposure was associated with an increased risk of irAEs in all enrolled cancer patients treated with ICIs. However, it is important to note that the relationship between aspirin use and irAE risk varies across different tumor types, types of irAEs, and various ICIs. Our research findings highlight these distinctions.

As a well-known non-selective COX inhibitor, aspirin irreversibly acetylates the active sites of COX-1 and COX-2, thereby reducing their enzyme activity (Ornelas et al., 2017). COX-1 mainly mediates the formation of physiological prostaglandins, such as Thromboxane A2 (TXA2), which in turn promotes platelet aggregation (Menter and Bresalier, 2023). Aspirin inactivates COX-1 and prevents the production of TXA2, thus acting as an antiplatelet and preventing thrombosis. More importantly, previous studies have confirmed the role of platelets in promoting tumor growth and metastasis (Lichtenberger and Vijayan, 2019). Rachidi et al. (2017) found that a protein called Glycoprotein A repetitions predominant (GARP) exists on the surface of platelets, which traps and activates Transforming growth factor-β (TGF-β). TGF-β is an immunomodulatory molecule that suppresses CD4 and CD8 T cells, allowing tumors to evade the immune system. Riesenberg et al. (2019) confirmed through a mouse model that the antiplatelet effect of aspirin can inhibit TGF-β signaling, thereby enhancing T cell function, and synergistically exerting anti-tumor effects with PD-1 blocker.

COX-2 is an inducer of enzymes that promote the synthesis of inflammatory prostaglandins, such as Prostaglandin E2 (PGE2), which can cause inflammation (Jin et al., 2023). Interestingly, PGE2 has been shown to regulate the function of various immune cells within the tumor microenvironment (TME), including myeloid-derived suppressor cells (MDSCs), dendritic (DC) cells, natural killer (NK) cells, CD4 and CD8 T cells, resulting in immune evasion (Zelenay et al., 2015; Böttcher et al., 2018; Bonavita et al., 2020). Moreover, PGE2 is capable of upregulating PD-L1 expression (Goto et al., 2020) and inhibit T cell receptor activation (Newick et al., 2016). The above study suggests that aspirin may exert immunomodulatory effects and enhance T cell activation by inhibiting COX2/PGE2 pathway (Wei et al., 2022; Jin et al., 2023).

Aspirin has been found to aid ICIs in breaking immune tolerance and amplifying the immune response (Zelenay et al., 2015). Unfortunately, it is important to note that immune activation is not limited to tumor-specific responses. Some researchers have proposed that activated effector T cells also attack normal non-tumor tissues while increasing their anti-tumor activity (Khan and Gerber, 2020; Ronen et al., 2022). T-cell receptor (TCR) sequencing studies have provided evidence to support this theory (Porciello et al., 2022; Sanromán Á et al., 2023). In patients treated with Ipiliumumab, researchers detected greater CD4 and CD8 T cell diversity in irAEs patients compared with those who did not experience significant adverse reactions (Oh et al., 2017). A recent work from Luoma and others has demonstrated the presence of a large number of CD8 T cells with high cytotoxicity and proliferation ability in the colon of patients with colitis, and these CD8 T cells are mostly from tissue-resident populations (Luoma et al., 2020). Together, these studies support that irAEs may be caused by the mobilization of a large number of T cells (Ramos-Casals et al., 2020). Other studies have shown that the presence of cross-antigens can also influence T-cell responses. In a study by Berner et al., 73 patients with NSCLC who received anti-PD-1 treatment were included, and nine common T-cell antigens were identified between tumor tissues and skin. This indicates that ICIs target both non-small-cell lung cancer (NSCLC) cancer and skin, leading to immune-related dermal toxicity while treating tumors (Berner et al., 2019). On the other hand, self-antigens from dying cells are captured by antigen-presenting cells (APCs) during tumor cell killing. These APCs then migrate to lymph nodes and activate more reactive T and B cells, These novel T cell clones may initiate a distinct immuno-editing wave, leading to adverse reactions (Yost et al., 2019; Baumjohann and Brossart, 2021).

Multiple clinical studies have investigated the potential of aspirin in enhancing the immune response in immunotherapy. Cortellini et al. (2020) reported that concurrent use of aspirin can improve overall response rate (ORR) among patients with solid tumors receiving PD-1/PD-L1 checkpoint inhibitors. Another study have highlighted that aspirin can prolong overall survival (OS) (Kostine et al., 2021). Furthermore, a meta-analysis suggested a significant intensification in progression-free survival (PFS) with concurrent use of aspirin and ICIs (Zhang et al., 2021). The above statements have demonstrated the synergistic effect of aspirin in ICIs. Therefore, aspirin may have underestimated immunomodulatory effects can amplify immune activation induced by ICIs. However, coins always have two sides. Over-activated T cells lack tumor specificity, so we have to consider the impact of aspirin on irAEs. We propose that aspirin may enhances T cell activation through inhibition of PGE2 and platelets, contributing to the increased irAEs.

Moreover, it has been shown that microbiota composition was a key factor in maintaining immune homeostasis, and may affect the occurrence of irAEs (Dora et al., 2023). Chaput et al. (2017) demonstrated that protective bacteria in the gut led to positive outcomes for patients who receive ipilimumab therapy, but also with a higher incidence of ipilimumab-induced colitis. Mouse models have shown that aspirin modulates the gut microbiota by enrichment of probiotics (Zhao et al., 2020; Brennan et al., 2021). This may also be one of the reasons why aspirin is associated with an increased risk of irAEs occurring (Figure 9).

Our research has uncovered a connection between the use of aspirin and an increased susceptibility to irAEs in pan-cancer patients. Delving deeper into our findings, we have identified a notably increased risk of irAEs among patients afflicted with specific cancer types, including lung cancer, mesothelioma, and pancreatic cancer. Conversely, a perplexing reduction in irAE risk has emerged in lymphoma patients. Remarkably, these observations constitute a novel contribution to the field, as they have not been previously documented in existing literature.

In stark contrast to prior retrospective studies, our comprehensive analysis has demonstrated robust statistical significance in support of these findings (Gandhi et al., 2020; Sieber et al., 2022). We posit that aspirin’s influence on the occurrence of irAEs may be mediated through the COX pathway, thereby shedding light on a potential mechanistic explanation. Furthermore, the intriguing divergence observed within the lymphoma subgroup warrants further investigation. While our data show a diminished risk of irAEs in lymphoma patients, it is essential to acknowledge that this subgroup comprises a relatively small sample size, constituting only 1.5% of the overall study population. It is conceivable that this statistical anomaly may be attributed to the limited representation of lymphoma cases, or it may signify the existence of hitherto undiscovered mechanisms that demand further exploration and scrutiny. In addition, aspirin use, prescribing status, or combination of aspirin with these conditions. These circumstances will also have an impact on our results (Colard-Thomas et al., 2023).

Our in-depth analysis revealed a significant association between the use of aspirin and a range of irAEs. Specifically, we observed that aspirin use markedly increased the risk of patients experiencing irAEs such as pneumonia, myocarditis, myositis, pericarditis, pancreatitis, colitis, and anemia. In contrast, the risk of irAEs related to conditions like rash, Stevens-Johnson syndrome, and thyroiditis was notably reduced. To further support our conclusions, we conducted a comprehensive review of previously published articles, seeking evidence that aligns with the associations we identified. Prior studies may not have fully considered the relationship between aspirin and irAEs or may not have detected these associations due to differences in research methodologies. Nonetheless, our study fills this knowledge gap and provides healthcare professionals with a more comprehensive understanding of aspirin’s role in irAE risk.

In summary, these findings underscore the need for heightened vigilance among clinicians when treating patients with immunotherapy, especially in cases related to irAEs affecting organs or systems such as the gastrointestinal tract, lungs, pancreas, heart, and anemia. However, it is also essential to consider an additional factor, namely, the widespread use of aspirin in cardiovascular disease treatment (Byrne and Colleran, 2020), where a patient’s history of cardiovascular conditions may be one of the factors contributing to the heightened risk of irAEs (Yousif et al., 2023). Therefore, a comprehensive assessment of the patient’s overall health and treatment needs is crucial.

Despite some limitations in our study and a lack of supporting mechanistic research, our research still provides valuable pharmacological guidance to the greatest extent possible. For example, when using aspirin in patients receiving PD-1 inhibitors, it is advisable to pay closer attention to indicators related to anemia, enteritis, pneumonia, and pancreatitis. Similarly, for patients undergoing PD-L1 inhibitor treatment, increased attention should be directed towards indicators associated with colitis, pericarditis, and pneumonia. Furthermore, in patients receiving CTLA-4 inhibitors, no association has been observed between aspirin and irAEs, although further research is needed to confirm this, in order to offer clinicians more precise treatment guidelines.

Overall, our study highlights the potential risks associated with aspirin use in patients receiving immunotherapy, particularly with regards to irAEs. These findings could inform clinical decision-making and improve patient safety.

The FAERS database, as a voluntary, passive, and non-mandatory reporting system, faces inherent challenges. These include incompleteness, inaccuracy, inconsistency, and delay in reporting adverse events. These limitations stem from various factors, primarily the lack of detailed patient characteristics, drug exposure information, and outcome details, such as the dose and duration of aspirin use, as well as whether patients received other treatment regimens and the sequence of medication. These factors may influence the associations observed and the study outcomes. Therefore, it is essential to carefully consider these limitations, particularly when interpreting the research results.

Furthermore, our analysis is influenced by the uneven distribution of cases within the database, with a higher number of lung cancer patients but significantly fewer patients with other cancer types. This non-uniform case distribution may introduce bias and restrict the generalizability and applicability of our study findings.

To overcome these limitations and provide more robust insights, further prospective clinical studies are urgently needed. Additionally, the mechanisms underlying the association between aspirin use and irAEs remain unclear, underscoring the need for fundamental research to address these uncertainties and advance our understanding of immunotherapy.

This study has revealed a significant association between aspirin usage and irAEs in cancer patients undergoing ICIs. It is important to note that this association exhibits variations depending on the specific cancer type, the nature of adverse events, and the specific type of ICIs being utilized. These findings underscore the importance of assessing the effect of baseline drugs, including aspirin, on the safety and efficacy of ICIs in tumor treatment, and tailoring treatment plans accordingly on an individual basis.