Researchers in Cork are studying the reasons why surgery for cancer can activate secondary tumours, writes Emma Napper.
New research is being carried out at Cork University Hospital to investigate a link between surgery and the spread of cancer. The aim of the project, funded by the Health Research Board, is to discover why patients who have undergone surgery for a cancer tumour are so likely to experience secondary tumours in other parts of their bodies.
"For 100 years, surgery has been the main cancer treatment," explains Prof Paul Redmond, the leader of the project. "Sixty per cent of all cancer treatment is surgery; however, one third of patients successfully cleared of their tumour will go on to develop secondary growths."
Redmond, along with Dr Calvin Coffey of UCC, believes that the body's healing process after surgery actually encourages secondary cancer growth.
Cancer cells from an initial tumour may escape into the bloodstream before surgery and attach themselves to other organs in the body, such as the lungs and liver. The cells then lie dormant, waiting until they get a signal to grow. Redmond and Coffey believe that this signal may be a chemical called vascular endothelial growth factor (VEGF), which enters the bloodstream after surgery.
VEGF causes new blood vessels to grow, and is released by the body after an operation to help mend cuts and fight infections. "Whenever you make an incision, the body wants to heal, so it produces VEGF," Redmond says.
However, VEGF is also essential to cancer cells, as they need a good blood supply to grow and multiply. The VEGF travelling round in a patient's blood may "provide the ideal environment for a dormant tumour to grow in another part of the body," explains Redmond.
It is not just the wounds from surgery that cause complications. Patients may also suffer secondary cancers because of the extra bacteria that enter the body during surgery. These bacteria come from the gut, and during any operation or stressful situation the body directs more blood to essential organs such as the brain and heart and moves blood away from the gut, temporarily starving it of oxygen. Soon afterwards, the blood flows back into the vessels surrounding the gut, but the huge fluctuation in oxygen levels damages the cells there and can cause the gut's delicate lining to become tattered and torn.
Bacteria that are normally held safely inside the gut move through the damaged lining into the bloodstream, where they release toxins. These toxins in turn stimulate VEGF, which is produced in order to fight the bacteria.
Redmond also reports that bacteria could directly cause the growth of secondary cancers by attaching themselves to dormant cancer cells and triggering them to multiply.
THOSE at most risk from secondary cancers caused by surgery are people suffering from breast and colon cancer, because these types of cancer require a major operation.
However, not all types of cancer require such surgery. For example, skin cancer patients can be treated without invasive operations. This means that, in the short term, skin cancer patients are less likely to produce VEGF and, under normal circumstances, have a lower chance of secondary cancers.
Redmond and his team are also working on secondary cancers caused by stress. Even in people who have previously been cleared of cancer without a major operation, "secondary tumours can be triggered by a traumatic event, such as a car crash or the loss of a spouse", Redmond says.
This is because the stress of these events reduces natural defences so that the body can no longer keep the dormant cancer cells under control, allowing them to multiply.
Every year there are 20,000 new cases of cancer in Ireland alone, accounting for a quarter of all deaths. Lowering the number of secondary cancers would be a major step forward in controlling the disease. Redmond thinks that doctors are "missing a window of treatment" after surgery that could reduce the stimulation of secondary cancers. His team are currently investigating new agents that could block the production of new blood vessels around tumours.
Redmond also suggests that something as simple as eating "probiotic" yoghurt - containing lots of good bacteria - after surgery could reduce the amount of bad bacteria entering the blood.
This research is one of 51 new projects funded by the Health Research Board as part of a series of awards worth a total of €6.8 million. The awards, announced in June 2002, aim to support innovative research into biomedicine and health care. The work is also supported by Aid Cancer Treatment.