TRANSKRIPT 🔗
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So, this is going to be a bit of a deep dive into a subject called central node biopsy, which is complicated.
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A central node biopsy is an operation in which a surgeon finds and removes the first lymph nodes, the so-called central node or nodes, to which cancer cells are likely to spread from an initial cancer as it forms.
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It so happens that central node biopsy was in its infancy in the treatment of melanoma when I was starting my specialist training years as a plastic surgeon, and I was amongst one of the first specialists to perform this procedure for melanoma.
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So I've been taking central node biopsies for almost 30 years by now, and I was one of the plastic surgeons contributing to one of the big multi-center trials that contributed data to our understanding of the relevance of central node biopsy in melanoma care.
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When I was a consultant at St.
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Thomas' Hospital in London, that was 20 years ago.
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That was the multi-center selective lymphadinectomy trial number two, which understandably we then shortened to MSLT2.
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So to understand why the current New Zealand guidelines recommend that we sometimes perform a central node biopsy on some patients with melanoma but not on others, which may be why you're watching because you've been diagnosed with melanoma and you're searching for information, it may help you to understand a little of the history of how melanoma spreading to lymph nodes was treated in the past.
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How to treat the regional lymph node basins, in other words, the first group of lymph nodes to which an area of skin drains lymphatic fluid and therefore the first place to which malignant melanoma cells metastasizing in lymphatic fluid would be expected to spread, has been a contentious topic among surgeons for well over a century.
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Broadly speaking, one school of thought believed that the regional lymph nodes should be removed en bloc at the same time that a melanoma had been detected in the skin and removed.
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So you had your melanoma removed and then at the same time or within a few weeks you had the lymph nodes removed completely from either your neck or your armpit or your groin.
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Which of these areas was stripped of lymph nodes depended on where your melanoma was.
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So, for example, if it was on your arm, then the nodes from your armpit were removed.
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If it was on your face, then the lymph nodes from your neck were removed.
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Now the other school of thought advocated waiting to see if the lymph nodes became involved.
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And that was judged by an enlargement to be felt on examination, and only then removing those regional lymph nodes.
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This they argued would prevent the proportion of patients undergoing radical surgery who didn't need it, because that surgery had an associated complication rate, and they would avoid that, therefore, unnecessary surgery.
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Now, on the other hand, by the time patients had palpable disease in their lymph nodes, their tumours had generally already spread way beyond and into other organs and can no longer be cured by lymph node removal alone, if at all.
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There was really scant evidence to choose between what were really just opinions rather than evidence-based schools of data.
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And which of these management protocols you received as a patient depended largely on where you were in the world and which school of thought held sway.
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So in America and Australasia, you were more likely to be advised to have the more radical surgery, and in the UK, you were more likely to be monitored.
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One of several problems with these approaches was that patients whose melanomas had not metastasized derived no benefit from losing all their lymph nodes from a particular region.
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So that group would needlessly risk the morbidity and the complications of a major surgical procedure.
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Those whose tumours had metastasized were more likely to be diagnosed with metastatic disease at a stage where they already had multiple metastatic deposits and would come soon afterwards if they were in the group that got monitored.
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What we needed was to be able to select from within all melanoma patients that group of patients who were most at risk of having melanoma that had spread silently to lymph nodes, and then treat only them by removing their involved nodes.
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So it was this goal that underpinned the central node concept.
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And that's based on the finding that lymphatic spread of melanoma proceeds as an orderly process from A to B to C, and that's been predicted by mapping of lymphatic drainage from a primary tumour to the first central node in the regional basin.
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So in current practice for skin cancer, we know that central node biopsy is accurate at finding melanoma in the central node when the original melanoma develops in skin on the body below the collarbones.
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So it isn't indicated in the management of melanoma of the skin forming on the head and neck, because the spread of lymph nodes above the clavicle does not follow the reliable and predictable sequential pathway that it does below.
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And so the predictions from central node biopsies on the head and neck, when we did that research, did not give patients reliable
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prognoses.
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And for them, we should be using CT scans to assess their disease, not central node biopsy.
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And just for completeness and to avoid causing any confusion, I'll also just note that as well as for staging melanoma, central node biopsy is commonly used for staging breast cancer when the technique there is used in a different way, and it's also having its utility for staging other tumours being assessed at the moment.
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But I'm only talking here about the specific technique used for melanoma.
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So, where is our current state of knowledge?
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After large multi-center international studies on the relevance of central node biopsy for melanoma, in recent decades we've worked this out.
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The likelihood of metastatic spread to regional lymph nodes is proportional to the thickness of the primary melanoma when it's diagnosed and then removed in that minimal margin biopsy that I've spoken about in the past.
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That thickness of the primary melanoma is called the Breslau thickness, and it's named after Dr.
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Breslau, who's an American pathologist, who did that research and quantified the link between the thickness of melanoma and the risk that it would spread to lymph nodes.
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Breslau thickness is the only reliable prognostic indicator in melanoma until or unless there is metastatic disease identified in lymph nodes.
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So we still need to identify spread to lymph nodes if we possibly can, if we want to direct therapy reliably and promptly to patients who need it most.
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Ideally, then, one would be able to select for treatment those patients with the highest risk of metastatic spread and select only those patients with metastatic spread for lymph node surgery.
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That is where central lymph node biopsy, which we know is an investigation predicated on lymphatic metastases proceeding in an orderly fashion below the clavicle, enables mapping of the drainage from a primary tumour to the first, that the central node in the regional lymphatic base.
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That's where it comes into play.
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However, having a central node biopsy, and then if it is positive, going on to remove all the neighbouring lymph nodes in that area won't improve your survival, according to all our studies.
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And this is probably because we're better at spotting melanoma early, and so most positive central nodes contain only microscopic metastases.
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In other words, just a few melanoma cells rather than a lump of metastatic melanoma which has taken hold and overwhelmed the lymph node.
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And so in this situation, metastatic disease has already been adequately treated just by having the central node biopsy itself.
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Guidelines recommend patients are offered a central node biopsy when their melanomas are thicker than one millimeter and in some special cases thicker than 0.8 millimeters, and that's according to the recent iteration of the American Joint Committee on Cancer Guidelines.
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So if you're in America, that would be what was offered to you.
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That means we're diagnosing early micrometastatic spread when it's most likely and largely treating it surgically, insofar as we can.
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What should you do?
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There's negligible benefit from performing central node biopsy in patients whose primary melanoma is thinner than a millimeter.
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Again, with a couple of exceptions.
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So it's easy to say who shouldn't have a central node biopsy, it's that group.
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Who should?
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Central node biopsy performed according to consensus standards is accurately predictive of the nodal status of the regional lymph nodes in melanoma 99% of the time.
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So in other words, if a central node has no evidence of metastatic melanoma, then there's only a 1% chance that any of the other lymph nodes contains tumour.
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So it's an invaluable and accurate investigation for staging patients at most risk and treating micrometastatic deposits.
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And so I recommend it for those patients.
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Evidence suggests that for 70 to 80% of patients with micrometastases in the central node, there will be no other involved regional nodes.
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And so, in my view, there's no longer a case for extensive lymph node surgery in this group, and especially so as recent advances in immunotherapy and chemotherapy for melanoma are revolutionising treatment and survival for metastatic melanoma beyond the central node.
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I hope that helps.
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I'm Dr.
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Adam Greenbaum at Cutting Edge Plastic Surgery.