For years, it has been a mainstay of treatment to stop the spread of many cancers.
But is the removal of lymph nodes – tiny, bean-shaped nodules that filter waste and bacteria – really the best way to prevent tumour cells from migrating around the body? Mounting research suggests lymph nodes – found in their hundreds in the neck, armpits, groin and even behind the knees – are host to immune cells which play a crucial part in recognising cancer cells and destroying them.
Removing the nodes may, according to some scientists, weaken the immune system’s ability to detect and attack those cells.
Now researchers in Germany have found a way to harness the power of immune cells in lymph nodes to destroy cancer cells. It could mean that, rather than cutting them out to stop malignant cells spreading, lymph nodes could be used to fight cancer.
Lymph nodes act as filters to clean up lymph fluid – which is made up of water, proteins and fats, as well as bacteria, viruses and abnormal cells – as it passes through them.
They are also often the first port of call for cancer cells that have broken free from tumours in the breast, lung, stomach and liver, or from potentially deadly skin cancers called malignant melanoma.
These cells get swept along in lymph fluid and often settle inside the lymph nodes before travelling on to other vital organs.
In about 30 to 40 per cent of breast cancer cases, for example, tumour cells have already spread to lymph nodes in the armpit by the time the patient is diagnosed.
Removing lymph nodes – tiny, bean-shaped nodules that filter waste and bacteria – has been a mainstay of treatment to stop the spread of many cancers. They are found in their hundreds in the neck, armpits, groin and even behind the knees (picture posed by model)
For decades the common solution has been to surgically remove all of those nodes (most people have between 20 and 40 in one armpit alone). Called axillary node clearance, this significantly reduces the chances of any tumour cells lurking in the nodes spreading.
But it can lead to lymphoedema, a debilitating condition where fluid that usually drains through the lymph nodes instead collects locally – in the case of breast cancer, typically the arm – causing limbs to swell.
An estimated 400,000 people in the UK have lymphoedema; it can leave those affected struggling to get dressed or do everyday chores.
Treatment relies on massage to disperse the fluid or wearing compression stockings or sleeves to help push fluid round the system.
In recent years, the focus in breast cancer has shifted away from taking out all the potentially affected lymph nodes in favour of removing just one or two, called a sentinel lymph node removal.
This involves removing nodes closest to the tumour: if these are found to contain cancer cells, the remaining nodes may be removed.
If not, no further nodes are removed, and the risk of lymphoedema is dramatically reduced.
Data from Royal Marsden NHS Foundation Trust shows only around 5 per cent of breast cancer patients who have sentinel node surgery develop the swelling, compared with more than 30 per cent of those who have all nodes removed.
‘Lymphoedema can be catastrophic and life-changing,’ says Justin Stebbing, a professor of cancer medicine and oncology at Anglia Ruskin University.
‘And there are fewer and fewer cases where surgeons now perform axillary clearance [removal of all the lymph nodes] because the data shows that it doesn’t improve survival from breast cancer [compared to sentinel node removal].’
And the thinking is now that taking all the nodes out makes it harder for the patient to fight off cancer should it return.
In the latest breakthrough, researchers at University Hospital Wurzburg in Germany, claim they have found a way to activate the immune cells found in lymph nodes so they can attack and destroy cancer cells they come into contact with.
The team looked at the lymph nodes of patients with triple-negative breast cancer, an aggressive form of the disease.
Justin Stebbing, a professor of cancer medicine and oncology at Anglia Ruskin University, says: ‘It’s in the lymph nodes where the immune system gets its first good look at the cancer’
They found that when cancer cells reach the lymph node, they release proteins that bind to receptors on the surface of local immune cells to effectively switch them off.
But the scientists were able to stop the cancer proteins binding to the receptor by injecting drugs called mono-clonal antibodies.
In laboratory tests, the immune cells were then able to wipe out cancer cells in the lymph node and reduce the risk of the disease spreading, reported the journal Immunity last month.
Professor Stebbing says the findings highlight the importance of lymph nodes in fighting cancer.
‘It’s in the lymph nodes where the immune system gets its first good look at the cancer – and if it can’t look at it [because the nodes have been removed], it can’t kill it.’
But if that’s the case, why doesn’t this natural immune response always halt the march of cancer?
‘Probably because the immune system gets overwhelmed by the sheer number of cancer cells,’ Professor Stebbing told Good Health.
‘You need only one or two to get through and circulate round the body for the cancer to proliferate.’
A new study in Nature Immunology identified another type of cancer-fighting cell found only in lymph nodes – CD8 positive T-cells.
This discovery, says Professor Stebbing, adds to the evidence that lymph nodes aren’t just ‘passive filters’ but ‘training grounds for immune cells to grow into powerful fighters, and probably best left alone’.