A common painkiller has a side effect — it seems to fight cancer too

Diclofenac, a common anti-inflammatory painkiller, has ‘significant’ anti-cancer properties, according to research published in the journal ecancermedicalscience.

The investigation into diclofenac was carried out by the Repurposing Drugs in Oncology project, an international collaboration aiming to find new uses for existing and widely used non-cancer drugs.

The drug is usually used to treat pain in conditions such as rheumatoid arthritis, as well as migraine, fever, post-operative pain and joint pain.

The researchers say that diclofenac, which is cheap, safe and accessible, may improve the effectiveness of other cancer treatments such as chemotherapy and radiotherapy. They believe there is enough evidence to start clinical trials on the use of diclofenac in cancer treatment.

The study’s author Pan Pantziarka said: ‘It’s still somewhat surprising that there is still so much we don’t understand about how many of the standard drugs we use every day, like diclofenac, work. But the more we learn, the more we can see that these drugs are multi-targeted agents with interesting and useful effects on multiple pathways of interest in oncology.’

He said the drug’s ability to treat cancer was ‘potentially huge’, especially when given in the periods immediately before and after surgery. The advantage, the authors say, is in reducing the risk of post-surgical distant metastases — the spread of cancer from one part of the body to another — through the use of drugs like diclofenac.

‘After all, it’s metastatic disease that most often kills patients, not the original primary disease. It may also be that diclofenac may have actions which synergise with the latest generation of checkpoint inhibitors. The combination of the latest drugs in the anti-cancer armoury with some of the oldest is especially exciting,’ Pantziarka said.