Diclofenac, a commonly used nonsteroidal anti-inflammatory drug (NSAID), has significant anticancer properties. Preclinical and clinical data indicating the distinct anticancer effects of diclofenac were summarized by the Repurposing Drugs in Oncology project and published in ecancermedicalscience (doi:10.3332/ecancer.2016.610).

Although NSAIDs are promising in the prevention of cancer, this research suggests they may have a role in treating cancer as well.

Diclofenac is inexpensive and readily accessible, with over-the-counter status in many countries. This also means its safety has been carefully tested. Diclofenac is used to treat pain from rheumatoid arthritis and other musculoskeletal conditions, migraine, fever, acute gout, and postoperative pain. Generic forms are available.

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Based on a review of the literature, the researchers from the Repurposing Drugs in Oncology (ReDO) project believe that evidence supports clinical trials of diclofenac for cancer. Diclofenac has effects that are both dependent and independent of the COX pathway, distinguishing it from other NSAIDs. The research team stated that its multiple mechanisms of action make diclofenac “one of the more interesting NSAIDs in the context of cancer treatment.”

“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,” said Pan Pantziarka, PhD, member of the ReDO project and the Anticancer Fund, and first author of the study. “But the more we learn, the more we can see that these drugs are multitargeted agents with interesting and useful effects on multiple pathways of interest in oncology.”

Diclofenac has multiple mechanisms of action, particularly related to angiogenesis and the immune system. The ReDO team suggested it may have notable uses in the perioperative period. It may cut the risk of distant metastases occurring after surgery.

Metastatic disease is what most often kills patients, not the original primary disease, Pantziarka explained.

“It may also be that diclofenac may have actions which synergize with the latest generation of checkpoint inhibitors: the combination of the latest drugs in the anticancer armory with some of the oldest is especially exciting.”