Diclofenac, a common painkiller, has significant anti-cancer properties, researchers from the Repurposing Drugs in Oncology (ReDO) project have found.

ReDO, an international collaboration between the Belgium-based Anticancer Fund and the U.S.- based GlobalCures, has published their investigation into diclofenac in the open-access journal ecancermedicalscience.

Diclofenac is a well-known non-steroidal anti-inflammatory drug (NSAID) widely used to treat pain in conditions such as rheumatoid arthritis, migraine, fever, acute gout, and post-operative pain. Like other drugs examined by the ReDO project, diclofenac is cheap and readily accessible — and it’s already present in many medicine cabinets, so it has been carefully tested, according to ReDO researchers.

NSAIDs for cancer treatment?

NSAIDs have shown promise in cancer prevention, but there is now emerging evidence that such drugs may be useful in actually treating cancer. The ReDO researchers have examined the literature and believe that there is enough evidence to start clinical trials on the use of diclofenac in cancer treatment. For example, diclofenac taken in combination with other treatments, such as chemotherapy and radiotherapy, may improve their effectiveness, the researchers say.

They suggest that cutting down on the risk of post-surgical distant metastases through the use of drugs like diclofenac may represent a huge win in the fight against cancer.

Developed by Ciba-Geigy (now Novartis), the drug is available globally as a generic medication. In some countries, low-dose formulations of oral and gel DCF are available over-the-counter (OTC) as a general purpose analgesic or anti-pyretic. Common trade names include Voltaren, Voltarol, Cataflam, Cambia, Zipsor and Zorvolex.

As with all NSAIDs, long-term use of diclofenac is associated with a small increase in the risk of cardiovascular events, particularly myocardial infarction and stroke, the authors note, but “many of the agents currently being trialled (examples include sorafenib, imatinib and crizotinib) have greater toxicity and costs associated with them.”

The authors declare in the paper that they have no competing interests.

Abstract of Repurposing Drugs in Oncology (ReDO)—diclofenac as an anti-cancer agent

Diclofenac (DCF) is a well-known and widely used non-steroidal anti-inflammatory drug (NSAID), with a range of actions which are of interest in an oncological context. While there has long been an interest in the use of NSAIDs in chemoprevention, there is now emerging evidence that such drugs may have activity in a treatment setting. DCF, which is a potent inhibitor of COX-2 and prostaglandin E2 synthesis, displays a range of effects on the immune system, the angiogenic cascade, chemo- and radio-sensitivity and tumour metabolism. Both pre-clinical and clinical evidence of these effects, in multiple cancer types, is assessed and summarised and relevant mechanisms of action outlined. Based on this evidence the case is made for further clinical investigation of the anticancer effects of DCF, particularly in combination with other agents – with a range of possible multi-drug and multi-modality combinations outlined in the supplementary materials accompanying the main paper.