Mendelian Randomization Evaluates IL-6 Inhibition Effects on Hepatocellular and Colorectal Cancer RiskGenetic data shows tocilizumab does not cause specific cancers

medRxiv Published June 25, 2026 Study authors: Ranjha, M. M. A.; Munir, H. DOI ↗ Editorial oversight: Dr. Julia Lee, PhD · Oncology, Genomics & Drug Development

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Key Takeaway

Genetic modeling indicates no causal link between IL-6 inhibition and increased risks of hepatocellular or colorectal cancers.

This Mendelian randomization study investigated whether genetically proxied IL-6 inhibition, mimicking the mechanism of tocilizumab, influences the incidence of specific malignancies. The analysis focused on two primary cancer types: hepatocellular carcinoma (HCC) and colorectal cancer (CRC).

Data from both East Asian and European cohorts showed no significant causal link between IL-6 inhibition and HCC risk. In East Asian populations, the odds ratio remained near unity (0.997), while European data similarly demonstrated no statistically significant effect (0.984).

Similarly, results for colorectal cancer indicated no causal association with IL-6 inhibition in either population group. The findings suggest that targeting the IL-6 pathway does not appear to trigger increased malignancy risk based on these genetic proxies.

While the study provides evidence of safety regarding cancer risk for patients requiring tocilizumab, researchers note that larger genome-wide association studies are necessary to definitively evaluate more subtle effects specifically within hepatocellular carcinoma cases.

How this fits prior evidence

This finding extends prior evidence on tocilizumab's safety profile. Previous coverage indicated that IL-6 blockade maintains cardiovascular neutrality in rheumatoid arthritis, and tocilizumab showed early anti-inflammatory effects but no significant clinical benefit in STEMI or NSTEMI. The current analysis adds reassurance regarding cancer risk, finding no causal link to HCC or CRC. It also complements prior coverage on HCC treatments, such as immune-based combinations showing superior survival over sorafenib, by addressing a safety concern for IL-6 inhibition in this context.

Patients taking certain medications often worry about long term side effects, especially when it comes to cancer. This study looked at whether a specific medication called tocilizumab affects the risk of developing liver cancer (hepatocellular carcinoma) or colorectal cancer.

Researchers used a method called Mendelian randomization. This uses genetic markers as a proxy for drug exposure to see if there is a direct link between the medicine and cancer. They analyzed data from both East Asian and European populations to get a clear picture of the risks.

The results showed no significant causal effect on liver cancer in either group. Similarly, there was no evidence that the medication caused colorectal cancer in either population. While larger studies are still needed to fully confirm these findings for liver cancer specifically, this data offers reassuring evidence regarding cancer risk for patients using this treatment.

What this means for you:

Genetic modeling suggests tocilizumab does not cause an increased risk of liver or colorectal cancers.

Common questions

Does tocilizumab increase the risk of liver cancer?

The study found no significant causal effect on liver cancer (hepatocellular carcinoma) for either East Asian or European populations. While more specific research is needed to fully confirm these results, the current genetic data suggests that the medication does not increase this specific cancer risk.

Does tocilizumab cause colorectal cancer?

The study found no causal effect on colorectal cancer in either East Asian or European populations. The data indicates that taking this medication is not linked to an increased risk of developing colorectal cancer based on the genetic markers tested.

Who was included in this study?

The researchers looked at data from both East Asian and European populations. This helped them determine if there were different risks for people of different backgrounds when considering the impact of tocilizumab on liver or colorectal cancer.

Study Details

Study typeMeta analysis

EvidenceLevel 1

PublishedJun 2026

View Original Abstract ↓

Background: Interleukin-6 (IL-6) signalling drives chronic inflammation and is therapeutically targeted by tocilizumab, an approved IL-6 receptor inhibitor. Whether genetically proxied lifelong IL-6 inhibition causally influences the risk of hepatocellular carcinoma (HCC) or colorectal cancer (CRC) remains unanswered. Prior single-variant estimates from pooled observational data are methodologically limited and may reflect confounding. Methods: A two-sample drug-target Mendelian randomization (MR) study was conducted. Four independent cis-acting protein quantitative trait loci (pQTL) variants within the IL6 and IL6R gene loci (rs2228145, rs4129267, rs7529229, rs1800795) were selected as genetic instruments , with F-statistics ranging from 32.3 to 120.5, confirming instrument strength. Outcome data were obtained from four independent genome-wide association studies: HCC from BioBank Japan (BBJ; 1,866 cases, 195,745 controls), HCC from FinnGen Release 10 (674 cases, 218,118 controls), CRC from a European meta-analysis (19,948 cases, 12,124 controls), and CRC from BBJ (7,062 cases, 195,745 controls). Causal estimates were derived using inverse variance weighted (IVW) regression as the primary method, with MR-Egger and weighted median analyses as sensitivity methods. Cochran Q statistics assessed heterogeneity and MR-Egger intercept testing assessed directional pleiotropy. Results: Genetically proxied IL-6 inhibition showed no significant causal effect on HCC risk in East Asian populations (IVW odds ratio [OR] 0.997, 95% confidence interval [CI] 0.903 to 1.101, p=0.953) or European populations (IVW OR 0.984, 95% CI 0.802 to 1.208, p=0.880). Similarly, no causal effect was observed on CRC risk in European populations (IVW OR 1.015, 95% CI 0.957 to 1.075, p=0.623) or East Asian populations (IVW OR 0.999, 95% CI 0.948 to 1.052, p=0.971). Sensitivity analyses confirmed the absence of directional pleiotropy and heterogeneity across all four analyses. Leave-one-out analyses demonstrated that no single instrument drove the null findings. Conclusions: Genetically proxied IL-6 receptor inhibition, modelling the therapeutic effect of tocilizumab, showed no causal effect on HCC or CRC risk across four independent cohorts and two ancestries. These findings do not support a role for IL-6 pathway inhibition in the prevention of these cancers and provide reassuring genetic safety evidence regarding cancer risk in patients receiving tocilizumab. Larger HCC-specific GWAS are needed to definitively evaluate modest effects in this cancer type.

Mendelian Randomization Evaluates IL-6 Inhibition Effects on Hepatocellular and Colorectal Cancer RiskGenetic data shows tocilizumab does not cause specific cancers

How this fits prior evidence

Common questions

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