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A large-scale study led by the International Agency for Research on Cancer (IARC) has found that regular use of pharmaceutical opioids is associated with a higher risk of developing several cancer types. In this study, published today in eClinicalMedicine, regular use of pharmaceutical opioids was linked to a higher risk of developing cancers previously known to be associated with opium consumption, including cancers of the lung, bladder, larynx, pancreas, and oesophagus.
This study analysed data from nearly half a million participants in the UK Biobank cohort study, who were cancer-free at baseline and were followed up for more than a decade. It also integrated genetic evidence from 14 genome-wide association studies, which strengthened the findings. Use of stronger and longer-acting opioids was linked to higher cancer risks than use of weaker and short-acting opioids over the follow-up period. The increased risk was observed both among participants who smoked cigarettes and among those who had never smoked. In contrast, no increased risks were found for cancers not previously associated with opium use, such as cancers of the prostate, breast, colon, endometrium, kidney, ovary, and brain.
These findings highlight the need for further research to replicate the results, to determine whether the observed associations are causal, to quantify their magnitude, and to clarify their clinical implications.
It is important to emphasize that these findings should not be interpreted as grounds for immediate changes to clinical practice or prescribing guidelines. Opioids remain on the World Health Organization (WHO) Model List of Essential Medicines and are recommended in WHO guidelines as evidence-based treatments for managing moderate to severe pain, particularly for cancer pain, palliative care, and acute pain (such as post-surgical or trauma-related pain), as well as for treating opioid use disorders. WHO stresses that opioids should be prescribed according to evidence-based protocols to minimize risks of misuse, dependence, and adverse effects. WHO advocates for balanced policies that prevent both over-restriction, which can lead to untreated pain, and under-restriction, which can contribute to misuse, diversion, and opioid-related harms.
Sheikh M, Domingues A, Alcala K, Langdon R, Mariosa D, Feng X, et al.
Regular use of pharmaceutical opioids and subsequent risk of cancer: a prospective cohort study and Mendelian randomization analysis
eClinicalMedicine. Published online 11 November 2025;
https://doi.org/10.1016/j.eclinm.2025.103439
