Opioid overdose is rare in cancer patients, but risk rises with high doses, Ontario study finds

Opioids are essential for cancer pain, but there is little data on how often they lead to overdose in oncology. A population-based study in JAMA Network Open used linked Ontario health records (ICES) to follow 554,316 adults diagnosed with solid tumour cancers between 2013 and 2020, up to the end of 2024.

Key findings

• 1,591 people (0.3%) had at least one non-fatal opioid overdose and 191 (0.03%) a fatal one.
• Risk was highest in the first year after diagnosis and in advanced disease: compared with stage I, the overdose rate was about 2.6 times higher in stage III and 6.2 times higher in stage IV.
• After adjustment, any opioid prescription in the previous 30 days was associated with a 71% higher overdose rate (HR 1.71), and a high dose (≥50 mg morphine-equivalent per day) with roughly 3.5 times the rate (HR 3.47).
• The risk grew with each month of high-dose prescribing, and the association held in patients without opioid use disorder.

The authors conclude that opioids should be prescribed at the lowest effective dose, with close monitoring and routine assessment of overdose risk — not that patients should go without pain control.

Limitations

This is a retrospective observational study of administrative data: it shows associations, not that prescriptions caused the overdoses. Prescription records do not capture how patients actually took their medication or non-prescribed drug use, overdoses that never reached the health system may be missed, and results from Ontario may not apply everywhere.