Patient information on sentinel node biopsy
Many patients with newly diagnosed melanoma have heard about the test called "sentinel node biopsy", otherwise known as SLNB.
This test was a great idea that was developed in the early 1990's.
Here is the background :-
Melanoma can spread throughout the body. This is why it can be fatal. The most common body location that melanoma spreads to is a lymph node in a region of the body. For example, a melanoma on the skin of the leg may first spread to a lymph node in the groin.
Many decades ago, it was considered that anyone with a melanoma on the leg should also have their groin lymph nodes routinely removed. The idea was that this would stop this lymph node spread. The idea did not work. It turned out that the groin surgery did not improve the patient's chances of surviving their malignancy. However, patients suffered numerous complications, including significant long term disability at times.
This idea of excising all the regional lymph nodes was routine in the 1970s and 1980s. It all came to a stop when we realized that it only harmed patients.
SLNB became the next excellent idea. What if we only removed lymph nodes in those patients who already had a small amount of melanoma in their lymph nodes when their melanoma was diagnosed? What if we could identify the first lymph node the melanoma might spread to? We could just remove that one node through a quite small operation. Then this single lymph node could be examined by expert melanoma pathologists. If it showed no melanoma, the patient would be advised to have no further surgery. However, if this lymph node showed to have a little bit of melanoma in it, then those patients and only those patients would then progress to have all lymph nodes in that region of the body removed surgically.
It was a great idea. Experts around the world, but most notably at the John Wayne Cancer Hospital in Santa Barbara California, developed the techniques and technology to make the idea feasible.
Once the technique was being used widely, the next step was to test whether its promise would be realized.
A very large clinical trial commenced. Around the world in many centres, patients were randomized to either have the SLNB test or not. Those who had the test and had a positive result went on to have remaining lymph nodes in the region excised.
An interim report of that large trial has now been published. Unfortunately patients who had the intervention were no more likely to survive their melanoma than patients who did not have the intervention. 87% of patients in both arms of the trial survived 5 years. There was no difference.
So a good idea that offered much promise has unfortunately not resulted in the improved outcomes for melanoma patients we had wished and hoped for.
Patients suffered complications without gaining any survival benefit.
Various secondary analyses of the SLNB trial have been discussed. Some of the people who developed the test feel that there is a subgroup of patients who still might have a disease progression or survival benefit by having the SLNB test. However academics throughout the world, including many in Australia, have dismissed these misleading sub analysis claims.
The SLNB test does, however, provide added information for some patients regarding their chances of surviving this dangerous tumour. The most important feature of a melanoma in predicitng how severe it might be is the "Breslow thickness" of the melanoma. Your doctor will discuss this Breslow thickness of your tumour with you.
For some patients, having the SLNB test brings them further accuracy on their future survival prospects. Some patients want that added information and are willing to undergo the test and risk the complications to find out this information.
If you have a melanoma and are considering SLNB, you must be aware that while the test might give you added information about your prospects, it will not improve your survival chances, it will not help doctors decide what treatment could be offered next and it is a procedure in which around 10% of patients suffer complications.
Doctors no longer even know whether to remove the remaining nodes in the event that the SLNB test is positive. A further major clinical trial is helping us try to answer this question.
Dr. Anthony J Dixon.