Cancer and Substance Use

Alcohol and tobacco cause several cancers, while other substance-related risks and treatment effects need separate consideration. Risk evidence cannot establish why one person developed cancer. During cancer treatment, fever or becoming suddenly unwell needs urgent medical advice. Sudden confusion needs immediate medical help.

Cancer and substance use can meet in three different ways: an exposure can increase the chance of developing cancer, a substance can affect treatment, and living with cancer can change how someone uses substances. These questions need different evidence.

Alcohol and tobacco are established causes of several cancers. That does not mean every cancer is caused by substance use, or that a diagnosis reveals someone's history. Changing exposure can still be useful after diagnosis, especially stopping smoking, but nobody can promise a particular outcome.

Cancer care should take pain, distress, dependence and practical difficulties seriously together. Tell the care team about alcohol, nicotine, cannabis, other drugs, prescribed medicines and supplements so they can check the actual combination. Do not abruptly stop alcohol or benzodiazepines if physical dependence may be present; get medical advice about a safe plan.

During cancer treatment, fever, chills or becoming suddenly unwell needs urgent contact with the cancer team or urgent medical care. Follow the team's emergency instructions. Sudden confusion needs immediate medical help, whatever the suspected cause. Severe breathing difficulty or inability to wake needs emergency help. Do not wait to decide whether a substance, treatment or the cancer is responsible.

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