London: Giving cancer patients aspirin at the same time as immunotherapy could boost the effectiveness of the treatment, says a new study.

The researchers found that combining immunotherapy with aspirin or other COX inhibitors substantially slowed bowel and melanoma skin cancer growth in mice, compared to immunotherapy alone.

Aspirin, commonly prescribed for pain relief, is part of a group of molecules called COX inhibitors.

“Giving patients COX inhibitors like aspirin at the same time as immunotherapy could potentially make a huge difference to the benefit they get from treatment,” said study author Caetano Reis e Sousa from Francis Crick Institute in London.

Skin, breast and bowel cancer cells often produce large amounts of prostaglandin E2 (PGE2) molecule that dampens down the immune system’s normal response to attack faulty cells, which helps cancer to hide.

It is a trick that allows the tumour to thrive and may explain why some immunotherapy treatments have not been as effective as hoped.

Aspirin and other COX inhibitors stop the production of PGE2 and help reawaken the immune system, the study said.

“We have added to the growing evidence that some cancers produce PGE2 as a way of escaping the immune system. If you can take away cancer cells’ ability to make PGE2 you effectively lift this protective barrier and unleash the full power of the immune system,” Sousa noted.

The study was published in the journal Cell.