A combination of erectile dysfunction drugs and the flu vaccine could prevent the spread of cancer, groundbreaking new research suggests.

The study, published in OncuImunnology, showed that this unconventional strategy may be able to help patients’ immune systems kill off cancer cells left behind after surgery.

“Surgery is very effective in removing solid tumours,” said Dr Rebecca Auer, head of cancer research at The Ottawa Hospital and associate professor at the University of Ottawa, the senior author of the report.

“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.”

The treatment was successfully tested in a mouse model that mimics the spread of cancer.

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Researchers counted the number of metastases – secondary malignant growths away from the primary site of cancer – in mouse lungs and observed a 90 per cent drop.

“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.”

It is now being evaluated in a world-first clinical trial that will involve 24 patients who are undergoing abdominal cancer surgery at the Ottawa Hospital.

The trial will evaluate the safety of the treatment and observe changes in the immune system once sildenafil (Viagra), tadalafil (Cialis) and an inactivated influenza vaccine (Agriflu) take effect.

The study will determine whether giving Cialis five days prior to surgery, on the day of surgery – along with the influenza vaccine – and cialis 10 days after surgery will affect the chances of the spread of cancer following surgery to remove tumours.

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“We’re really excited about this research because it suggests that two safe and relatively inexpensive therapies may be able to solve a big problem in cancer,” said Dr Auer. “If confirmed in clinical trials, this could become the first therapy to address the immune problems caused by cancer surgery.”

Usually, natural killer immune cells play a major role in killing metastatic cancer cells but surgery can create myeloid derived suppressor cells (MDSC), another kind of immune cell, which block the natural killer cells.

Researchers found that erectile dysfunction drugs block MDSCs, which allow the natural killer cells to fight the cancerous cells while the flu vaccine further stimulate the natural killer cells.

Dr. Auer noted that although erectile dysfunction drugs and the flu vaccine are widely available, people with cancer should not self-medicate.