A mix of Viagra and the flu vaccine could treat cancer, say researchers

Cancer patients should not self-medicate, researchers warn. Photo / AP

A combination of Viagra and a flu vaccine could treat cancer, surprising new research suggests.

The unconventional strategy invigorates the immune system to attack tumour cells left lingering after surgery, when the body is vulnerable.

Testing the method in mice with lung cancer, Canadian researchers saw a 90 per cent reduction in the spread of the disease.

The study was such a success that 24 human stomach cancer patients will now test the combination in a clinical trial that could pave the way to it being approved.

Normally, immune cells called natural killer (NK) cells play a major role in killing metastatic cancer cells.

But surgery causes another kind of immune cell, called a myeloid derived suppressor cell (MDSC), to block the NK cells.

Dr Rebecca Auer's team at the University of Ottawa has found that erectile dysfunction drugs block these suppressor cells, which allows the natural killer cells to do their cancer-fighting job. The flu vaccine works to further stimulate the natural killer cells.

"Surgery is very effective in removing solid tumours," said senior author Auer, surgical oncologist and head of cancer research at The Ottawa Hospital.

"However, we're now realising that, tragically, surgery can also suppress the immune system in a way that makes it easier for any remaining cancer cells to persist and spread to other organs.

"Our research suggests that combining erectile dysfunction drugs with the flu vaccine may be able to block this phenomenon and help prevent cancer from coming back after surgery."

The current study investigated sildenafil (Viagra), tadalafil (Cialis) and an inactivated influenza vaccine (Agriflu) in a mouse model that mimics the spread of cancer (metastasis) after surgery. Auer is now leading the first clinical trial in the world of an erectile dysfunction drug (tadalafil) and the flu vaccine in people with cancer.

It will involve 24 patients at The Ottawa Hospital undergoing abdominal cancer surgery.

The team warned that cancer patients should not self-medicate with this combination, even though both the drug and vaccine are widely available.