Lighting up our sentinels
15 February 2016
Traditionally, gynaecological cancers (those found in a woman’s reproductive system) are diagnosed using an invasive and potentially dangerous technique that often leads to additional health concerns for the patient – as if coping with the cancer itself wasn’t enough. Fortunately, scientists working in Professor Ahmed Ahmed’s lab at the WIMM have recently developed an alternative method to diagnose these cancers, which could revolutionise how doctors treat women suffering from this disease. Eva Masmanian explains more.The substance transported by the lymphatic system is called lymph, which comes from the fluid that bathes and nourishes the tissues of the body. Lymph is formed when this fluid collects in the lymphatic vessels, as seen in this image (left)
Infectious agents like bacteria and viruses collect in lymph, and so the lymphatic system is continually monitored by small organs called lymph nodes (seen as swellings in the picture). White blood cells concentrate at these lymph nodes and help to fight and remove these infectious agents.
However, lymph can also carry more sinister cargo. In patients with aggressive forms of cancer, lymph can carry cancer cells that have left the site of the original tumour, and have gone on to initiate another tumour somewhere else in the body. Cancer cells can thus also be found in lymph nodes – a fact exploited by doctors when trying to diagnose cancers.
The ‘staging’ of a cancer is an assessment of how much a cancer has spread. The most reliable practice for staging a gynaecological cancer (cancer in a woman’s reproductive system) is to surgically remove at least ten of a patient’s lymph nodes to check for the presence of cancer cells. This is called a systematic lymphadenectomy.
A systemic lymphadenectomy is a very invasive procedure that can lead to many complications, including widespread build-ups of lymph that cause swellings and discomfort (lymphoedema). However, a new technique called sentinel lymph node mapping has been recently developed to try and overcome these issues, whilst still maintaining a high cancer detection rate.
As cells belonging to a cancer in a specific location will spread in a characteristic pattern due to the layout of the lymphatic vessels, we can identify the first lymph node that would contain any metastatic cancer cells – this is termed the sentinel lymph node (SLN). We can therefore see if a cancer has spread by identifying its specific SLN, and selectively removing this lymph node to test for the presence of cancer cells, hence minimising side effects.
Identification of SLNs involves the use of imaging techniques, which conventionally involve the use of a radioactive substance – but as you can imagine, even low levels of radiation may potentially have adverse side-effects, and therefore this technique is less than ideal.
So what alternative methods could be used to identify SLNs? A team of researchers from the Ahmed Ahmed lab at the WIMM has recently published a study in BMC Research Notes to assess the use of a fluorescent imaging system in SLN mapping.
This technique involves the injection of one or more fluorescent dyes into the region of the tumour, so that the path of the dye follows the lymphatic drainage of the tumour. The dye is injected before surgery, and a specialised camera is used by the surgeon to detect fluorescence in real time as it drains from the tumour site into the lymphatic system. The fluorescent dye will drain to the lymph node closest to the tumour, and will ‘light up’ the SLN to be removed.
The team led by Ahmed Ahmed have shown that a custom-made near infrared (NIR) fluorescence imaging system can be used to detect SLNs at a rate that exceeds conventional methods based on blue dye and/or radioactive tracer, without any compromises to safety. Once the procedure was optimised, a 100% SLN detection rate was achieved and no false negatives were detected.
The results of this study hold great promise for the use of fluorescence in SLN detection for gynaecological cancer, eliminating the need for invasive and dangerous surgery. These findings are the first steps towards providing a safer, effective method of diagnosing and treating gynaecological cancer, offering hope to the thousands of women who suffer from this devastating disease.
Post edited by Bryony Graham and Ahmed Ahmed.