Doctors should carefully consider the reasons for continuing opioid use among cancer survivors, say Canadian researchers.

Cancer survivors should be cautious about inappropriate or unnecessary use of opioids well after their diagnosis, warn experts.

A Canadian study, published in journal Cancer, found cancer survivors were 1.2 times more likely to be prescribed opioid painkillers than those who'd never had cancer.

This increased rate of opioid prescriptions remained true among survivors even ten years after the initial cancer diagnosis.

Researchers at the Institute for Clinical Evaluative Sciences in Toronto and an associate professor with the University of Toronto in Canada analysed information dating back to 2010 on more than 8500 adults at least five years past a cancer diagnosis.

They were matched with the same number of individuals without a prior cancer diagnosis based on sex and calendar year of birth.

Over a 36-month period, the average number of opioid prescriptions filled by survivors was 7.7, compared with 6.3 for the others.

"This study demonstrates substantially higher opioid prescribing rates among cancer survivors, even long after attaining survivorship," the study's authors said.

"This raises concerns about the diagnosis and management of chronic pain problems among survivors stemming from their cancer diagnosis or treatment."

Lead investigator Dr Rinku Sutradhar says doctors should carefully consider the reasons for continuing opioid use.

"Physicians providing primary care to cancer survivors should consider close examination of reasons for continued opioid use to differentiate chronic pain from dependency," Dr Sutradhar said.

Cancer Council boss Professor Sanchia Aranda says overall this is an "interesting study" with valid conclusions but given it was a retrospective study there are limitations to the data.

She says its important to understand some cancer survivors have ongoing healthcare issues and that may be appropriate to manage with opioid analgesics.

While it's not unheard of for some cancer survivors to still need opioids 10 years after a diagnosis, it's uncommon.

Prof Aranda agrees anyone who's receiving opioid medications needs careful management not just repeated prescriptions.

"Cancer survival should be about returning people as close as possible to the life they had before, and that there are always side effects and consequences of ongoing use of opioids and so careful management by somebody trained in chronic pain is needed," said Prof Aranda.