Operating room technology
body’s look and shape. An amount of excised tissue is considered “enough” if no cancer cells are present at its outer edge, which is called a negative margin. A positive margin, on the other hand, means that there are cancer cells at the edge of the tissue and therefore that cancer is likely still in the body – and that the patient will have to come back for another operation. But how much tissue to remove to achieve a negative margin, and the best method to determine that margin, are questions the field is still trying to find answers to. “There’s no perfect methodology,” says Dr Anees Chagpar, professor of Oncological Surgery at Yale School of Medicine. “Ideally, you want something that is fast, that is cheap, that is efficacious, and that drops your positive margin rate.” That’s a tall order in the medical world, where efficacy and cost are often strongly correlated. So just how close are we to achieving it?
Margins for different cancers For all tumours that need to be surgically removed, the aim is to take out all of the cancer cells. But the best way to go about this can be a different conversation depending on the location of the tumour. With rectal cancer, for example, the area around the rectum is quite large and trickier to assess than other areas of the body, so some methods might not be useful, says Dr Sarah Blair, surgical oncologist and professor of Surgery at the University of California San Diego. There’s also the fact that margin assessment might not be as much of a priority if removing healthy tissue won’t affect the look of the body, nor the patient’s quality of life – as with colon cancer, she adds. For breast cancer, though, margins are crucial for breast-conserving surgery (lumpectomy), which aims to protect the shape and look of the breast as much as possible. This has been the focus of much research and development within the field. “Breast has really been ahead of the curve in de-escalating surgery,” says Dr Blair, who specialises in cancers localised to this area. “And one of the bigger issues for breast conservation is getting a negative margin.”
Imaging techniques We’re not totally there when it comes to accurately identifying cancer using imaging techniques, says Dr Chagpar, whose primary research focus is also breast cancer. “Images have a false positive and false negative rate, and they certainly do not have the level of detection that gets down to the cellular level. So call me a sceptic, I don’t think we’re ever going to get there until somebody invents glasses that help you see cells at a microscopic level.” It’s not perfect, but many operating rooms are still using x-ray to analyse tissue when it comes to
Practical Patient Care /
www.practical-patient-care.com
breast cancer. “Roughly 20% to as high as 40% of patients would still have a positive margin when that specimen was finally evaluated by pathology,” says Dr Chagpar. Plus, according to Dr Blair, an x-ray might not pick up cancer in every case, and it can be tricky to figure out where the cancer actually is from a two-dimensional image. There are a few three-dimensional imaging methods available, but the jury is still out on how well these work. One is micro-computed tomography (micro-CT), a 3D-scanning device. Studies on micro-CT for breast cancer have mostly been small, and the general consensus is that it isn’t necessarily better than a regular x-ray.
Scientists already use fluorescence techniques in microscopy to study cancer cells.
“Ideally, you want something that is fast, that is cheap, that is efficacious, and that drops your positive margin rate.” Dr Anees Chapgar
CT-scanning is also commonly used for pancreatic cancer, but evidence on how well it works is limited. One small 2022 study in the Korean Journal of Radiology found that CT scanning was good at identifying healthy tissue, but not great at spotting cancer cells. More recent technology has instead aimed to identify cancer by its physical properties. One such device is the MarginProbe, which uses an electromagnetic field to identify cancer cells by their electric properties.
“It does actually have some randomised control data,” says Dr Chagpar. “Not all of it has been consistent. Some have found a difference of reducing positive margins by up to a third. Other trials have not found a difference with MarginProbe.”
40%
Up to this number of patients still have a positive margin when their tissue specimen is evaluated by pathology.
Dr Anees Chapgar 45
Caleb Foster/
Shutterstock.com
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53
