Latest / Behind The Knife: The Surgery Podcast / Operative Standards for Cancer Surgery: Colon Cancer

Transcript

Operative Standards for Cancer Surgery: Colon Cancer · Behind The Knife: The Surgery Podcast

• BTK Colon Standard === [00:00:00] Welcome to a New Behind the Knife mini series on the operative standards for cancer surgery. This series will focus on the technical aspects behind these operative standards. The standards were developed through the American College of Surgeons Cancer Research Program and our concrete evidence-based recommendations on cancer surgery techniques critical to achieving optimal oncologic outcomes. Currently there are three volumes that cover 15 disease sites, and these are linked to in our show notes. Dr. Freeland and I are on the Education Committee for Cancer Surgery Standards Program, and today we'll discuss the colon cancer standard with Dr. George Chang. Dr. Chang is a professor and the current department chair of the Department of Colon and Rectal Surgery at MD Anderson Cancer Center. He was also the co-chair with Dr. Amy Halverson of the team developing the colon standards for the operative standards of cancer surgery volume one. So, Dr. Chang, thank you very much for being with us tonight. Welcome to the show, our first episode on the technical aspects of these cancer standards. So we're very excited to [00:01:00] discuss the technical aspects of a colectomy tonight. Thank you for joining us. Thanks very much. It's really a pleasure to be here, and thanks for asking me to come and participate. So Dr. Chang, can you please share some background on the manuals and how the decisions were made about which standard should be included? Thanks Lexi. The operative standards manuals for, for all the diseases were really designed to distill down the critical elements of, of oncologic surgery for the various different tumor types. And really the goal was to be able to succinctly outline the major steps to ensure that we achieve com a proper oncologic resection. And it was developed really by bringing together several experts and then iteratively going through a process that identified those critical elements, and in fact, we call it critical elements. In this process, we also identified some key questions, areas where there's [00:02:00] potential. Controversy or areas where, you know, further exploration may be helpful. And so we've outlined some of them in the manual as well. Yeah, that's very helpful. And, you know, obviously we will, we'll put links to the manuals in the show notes for this episode. And, I, we certainly encourage all trainees and even junior surgeons who are attendings to, to look through the manual. So. For the colon cancer elements specifically, so you guys laid out the critical elements to be abdominal expiration, the extent of bowel mobilization, resection, proximal vascular ligation, and regional lymphadenectomy. Multivisceral resection and removal of lymphadenopathy beyond the primary distribution. You know, for our time this evening, I think I really wanna focus on the extent of resection and the primary vascular ligation. I know when I saw you operate, those were the things that really. Changed my practice is, you know, learning [00:03:00] in general surgery, how to take a right colon out versus learning how to really get in that proximal vasculature. So I think it's a great place for us to focus. So why don't we start with the extent of bowel mobilization, resection, so, you can run through some of the obvious scenarios, but, you know, getting your opinion on, on the more complex, on the flexors and, and cancers that happen in those locations. Yeah. Thanks. I think this is. Probably one of the areas where we kind of take it for granted. You know, we learn, well, we have a right colectomy, or we have a sigmoid colectomy without really thinking through what is the operation and why are we doing it? And it really goes hand in hand in thinking about. How we handle the vascular ligation because the point of that obviously is to perform a complete lymphadenectomy appropriate to the location of the tumor. So when we think about the extent of resection in terms of the bowel, [00:04:00] it really is based upon the location of the tumor and it's feeding blood supply. The lymphatic drainage follows the feeding blood supply, and the definition of a complete oncologic resection is one that we have resection of the tumor along with the margin, and all of its regional. Lymph nodes. So let's take for example, a tumor that's located within the cecum. Its primary drainage is gonna be through the IOC colic vessel in patients in whom a right colic artery is present, which, as you know, there's a lot of variation in that anatomy, and it is not always present as a separate vessel off of the superior mesenteric artery. So for a tumor located in the cecum, then the appropriate resection is the IOC colic pedicle, and plus or minus the right branch of the middle colic. When we have a tumor located a little bit further down the colon, such as the ascending colon, [00:05:00] then that is clearly in between the distribution of the middle colic and the IOC colic there. The resection should include the IOC colic. And at the least the right branch of the ME colic distribution. Then by definition, that means that the extent of colonic resection is one that accounts for that vascular distribution. So the extent of colonic resection is really defined by which vessels are being ligated. And so that helps us to then think about. What is the sort of the right operation or the extent of resection? So we kind of generically refer to all of these as right colectomy, but really how we think about how much bowel we resect and what part of the colon is defined by the vascular anatomy in that way. So this is why a tumor in the hepatic flexor which gets drain, which has sort of, or. Let's go a little further over [00:06:00] in the transverse colon, closer to the hepatic flexure. That is why that is actually at the apex or to the left side of the right branch of the middle, which means that we need to do an extended right colectomy or an extended right colectomy means we are taking the IOC colic as well as the origin or the trunk of the middle column, because that allows us now to get the complete distribution. While there are some people who may argue that it is not appropriate to do simply a transverse colectomy because of a variety of concerns, including the residual blood supply or anastomotic integrity, taking these principles, it means that if we have a mid transverse colon tumor, then the distribution we need is the middle colic at its origin, and then we can put the two sides of the colon back together. Tumors of the splenic F flexure are handled in a similar fashion. We need the ascending left colic artery, which [00:07:00] derives its origin from the inferior mesenteric artery, and the left branch, at least, if not the entire middle colic trunk, depending on exactly where that tumor's located. So. With relations to the vessel. So if a tumor is a little more distal in the splenic flexor, then it will be between those, the left branch and the left colic. And if it's more proximal, it will invol include potential drainage. Through the right branch of the middle, therefore, the entire trunk should be taken. So this is the approach that we would add that the, that the operative standards advocates for or demonstrates, which is that we have to visualize that anatomy and then use that anatomy to determine what bowel gets resected. So hopefully that kind of helps to helps to clarify. I do wonder about that. So, you know, a lot of people. Push that, you know, if you take that middle colic, you should do an extended right. Your practice is to preserve the right colon. And and when you do that you know, [00:08:00] you're doing these all, I assume MIS, you know, you're doing that, that sort of side to side osmosis and creating that awkward mesenteric window. Do you have any advice kinda on how you handle that typically? Yeah, I agree. It's totally awkward, which is why I never do a side to side colo colostomy. So if it's a colon, colon anastomosis, I always do that as an end-to-end. Okay. Because I think it's just, you know, it's just very weird that anatomy. Now having said that, there's plenty of people who do that as a side to side. It's just, I think it puts more tension on the intersection and all of that. It's just not a natural lay of the bowel for me. And so I think part of the rationale for an extended rise is that ileocolic to the descending colon is a simpler anastomosis as well, is as we lose the ileocecal valve. We lose more colon. Most people tolerate that pretty well. But is it necessary? I don't think so. And if you are in Japan as an example, or Korea transverse colectomies get done all the time because the, it is based on [00:09:00] these princip, it's based on the anatomic principles of 10 centimeter margin on the bowel and then the vascular distribution. Mm-hmm. What about a scenario where you're not super confident exactly where the tumor is? Yeah. The colonoscopy says it's near the flexture, you know it's in the transverse colon and there's like kind of tattoo all over. Yeah. And it's just not totally clear. How do you handle that? Yeah, that's a great question. I think, you know, ideally you've done everything you can to localize if there's tattoo. So if there's tattoo, hopefully we know if it's tattooed proximal or distal to the tumor. If. Not, sometimes there's a clip and a x-ray that might help you, so that's another way to localize. We're really talking about small tumors because anything of substance you'll be able to see on the imaging. And so I think it's really critical to study the imaging before going into surgery so that, you know, and when you study the imaging, it's not just about finding the tumor within the longitudinal. [00:10:00] Anatomy of the colon, it's really about finding the tumor and the vascular anatomy to that part of the colon, so then, you know, and can plan the operation. So there is a tremendous variation in the vascular anatomy. And so, you know, it's important. So let's just take that junction between the descending colon and sigmoid colon as an example. It's quite possible, depending on the anatomy, that that tumor maybe is just a little further down the sigmoid. So let's just say that tumor is entirely in the distribution of, you know, what the vessel that some people regard, either as the first sigmoidal or the descending left colic artery. But in any case, it's that. It's that vessel that is entirely has its distribution from the superior rectal artery. You know, you, if you, if it were tumor were located there and you couldn't be a hundred percent sure, then the solution would be to resect the distribution of the inferior mesenteric artery, and then you could bring the descending colon down and do your anastomosis. That would be the, and, and on this side, and, and of course, [00:11:00] you know, of course, the key principle is ensuring adequate blood supply by observing the principles of resecting, the distribution of the blood supply, the resecting, the distribution of the lymphatic drainage associated with that tumor. We'll ensure that we have adequate blood supply to our anastomosis, but you all know. As in situations like rectal cancer, we often ligate blood supply and depend upon the marginal vessel to provide that supply to our conduit for the reconstruction. So the point I'm trying to make is, the first principle is understand the vascular anatomy. The bowel extent is dependent upon tumor location with relationship to that vascular anatomy, but it's not like. Okay. There's only one place that we can lag it in. We want to ensure that there's adequate margin on the bowel, ideally five to 10 centimeters. We wanna ensure that we've removed all the lymph nodes associated with that part of the bowel, and then we wanna ensure [00:12:00] that there's an adequate blood supply to the bowel we're putting back together. And generally speaking, if we observe these principles. Then the bowel will be well vascularized, right? Using the vascular anatomy as the guide, you know, to the extent of resection. So hopefully that helps. Alright. So can you walk us through your technical steps of how you would perform a right colectomy, say for a mass in the ascending colon? Yeah, so, again, we, if we go back to the principles that we outlined in the operative standards, our goal, now that we've defined which vessels we need to to identify, and we've defined what part of the bowel will be resected, now we have to think about, okay where do we perform? How do we per perform the resection? Where do we perform our vascular ligation? So, within the operative standards, this is one of the key [00:13:00] critical elements that we emphasize, which is proximal vascular ligation. What that means is that the lymphatic drainage of the, of the tumor within the bowel goes along the arterial supply, and we want to get to the origin of that arterial supply. So for a tumor in the ASCE colon, that means, you know, we need to. One, one of the primary feeding vessels is the ileocolic artery, and we would wanna ligate that at its origin from the superior mesenteric artery, or very close to, to that site. The, there's significant variation of the anatomy about not quite half the time it runs anterior. A little bit more than half the time it runs posterior to the superior mesenteric vein. So it's not to say you have to then mobilize the superior mesenteric vein completely and get to that origin. At the SMA, it, the, the ideal location for ligation of all of these vessels is just on the right side of the SMV. If we did that, we would be doing a complete lymph adenectomy. What in the [00:14:00] Japanese? Guidelines would be referred to as a D two lymphadenectomy. That is a increasingly more utilized terminology. The one, the concept of D one, D two, and D three lymph lymphadenectomy, but a complete D two lymphadenectomy or a complete resection of the mesentary. For the involved segment of the bowel, we'll ensure that we have a complete oncologic resection. We would also then in an ascending colon tumor, want to identify is there a r colic artery, and that should be lige in a similar way. And and if not present the next vessel then is the right branch of the middle colic artery. And of course, if it's an ascending colon, we'd have to look at that right colic distribution. Probably the safe approach is to also resect. The origin, the right branch of the middle colic artery. And that would then ensure that we have complete resection of all of the lymphatic drainage. The [00:15:00] principle again being the primary feeding vessels, and then the level of ligation being the origin of that vessel. I know it's a little difficult without visual prompts, but can you talk through how you you know, how you actually find those vessels? Are you, you're doing your vascular ligation very early in the case. How are you finding the origin? Are you tracking the ilio colic vein back to the SMB? How much of the SMB do you clear off? Yeah. And then how do you find that middle colic? Well, so first. The first step is really to identify that ileocolic pedicle, and we can do that with a little traction on the on the mesentery towards the cecum. But in reality, you can actually identify you often can see it even in an obese patient as being sort of a prominence within that mesentary. Our goal is to identify that plane, that avascular plane behind the ascending mesocolon. So we'll incise the peritoneum. Lift up on the mesentery [00:16:00] and if we are in the right spot, we will start to see that alar plane. We'll get that air dissection. If we're too distal on the mesentery that is overlying the IOC colic vessel, then we will not see that. So that's kind of the first cube. But then before really getting the vessel out, we'll take our incision. Across transversely, over the SMV and towards the SMA. Why do we do that? There are no anterior branches of the SMA or SMV, so it is a very safe plane, and so our goal is to first identify the superior mesenteric vein. The principle is we want proximal ligation and we want complete lymph ectomy that. Most sort of sured approach to do that is to utilize anatomy that anatomic landmarks that we can all identify readily. And so by dissecting through this tissue, [00:17:00] we can readily identify then the superior mesenteric vein so we can, you know, we can dissect through even in obese patients, this lympho adipose or this adipose tissue. Once we identify the SMV. Now we've got a safe plane because we can now work along that anterior SMV plane. So the peritoneum then gets incised. Towards towards the more proximal SMV, so towards the base or the root of the transverse mesocolon. We do that by putting some traction on the mesentery of the transverse colon and elevating that cephalad. That allows us, now that we've identified where the SMV is to follow up that plane by incising the peritoneum. In that direction and then exposing the anterior surface of the SMV. In so doing, then we can identify all the vessels, the tributaries to the SMV and then the branches of the SMA as well. It is very helpful to study the imaging so that you know, if you have an [00:18:00] s IOC colic artery that is anterior or posterior to the SMV, so you should. Definitely plan to anytime you do any kind of cancer surgery, you know, we should all be students of, of the imaging, right. And study the anatomy so that we know what we're doing. And again, we didn't discuss the first step being mobilization of the bowel. We discussed. The first step being actually identifying the vascular anatomy. And I think that's really critical because that helps us then to sort of, you know, be rooted and focused in these oncologic principles and ensuring the completeness of the resection. So once we've done that then, we've, we've identified the SMV. That means we know now where the IA, colic pedicle is gonna be. We can elevate that ia, colic, pedicle. And what I'm really describing now is sort of a minimally invasive approach, right? In an open approach, we would do similar principles, but the sequence might be a little bit different. But once we've now got the va, the ileocolic, pedicle elevated, we can isolate now the IOC colic artery and the vein. Just [00:19:00] on the right side of the SMV and then and then ligate that. Now it's a matter of following along that SMV really taking everything to the right side of the SMV and including it so that we have an intact mesenteric envelope that will be resect and we have completely resected. And this will then take us, if there's a right colic artery, we'll see it. The next vessel we'll identify following this plane of dissection is gonna be the gastrocolic trunk. The gastrocolic trunk is the tributary that comes draining the pancreas and the duodenum and the right colon into the SMV and as well as the gas gastro propole vein, right? They all come together to the gastrocolic trunk, sometimes called the Gastrocolic Trunk of Henley. So at that level, what we wanna do is identify the superior R colic vein. That superior r colic vein drains into the gastrocolic trunk just distal to the superior pancreatic duodenal vein. So you can tell where, where that is, because that [00:20:00] vein ISS heading down towards the pancreas and duodenum. And then there is this vein draining in from the ascending meso colon. We've identified that because we've done some dissection. The Mesentary, the retro mesenteric plane or tos plane behind the ascending meso colon anterior to the duodenal second portion of the duodenal and the head of the pancreas. Right? We've done all of that. So we've elevated that mesentary and we're looking at the undersurface of the ascending me mesial, colic. Plane, fascial plane. So then we can see where that superior right colic vein is coming. So that vein is ligated there and now that allows us to have essentially complete detachment of all of the blood supply to that right side of the colon. The next vessel left then is the middle colic artery. And because we're coming up along the SMV, which is just adjacent to the SMA, we can identify then the origin of the [00:21:00] middle colic. As we come up to the base of the transverse meso colon, now our plane of operation is now gonna be away from the retroperitoneum, right? Because we've elevated the transverse meso colon. Now, the middle colic artery is not a mesenteric structure, and what I mean by that is the middle colic origin. It can be considered in some ways a retroperitoneal structure. What I mean by that is. It is, it does not have, it doesn't have a peritoneal mesentery typically on both sides, right? It does by the time it bifurcates and gives us a left and the right branch. But the origin itself is actually within that, you know, perivascular, sort of, adipose tissue. So that makes it kind of, in most cases, it makes it kind of tricky to identify. If we follow this and then identify follow this up along the SMV plane and now we can start incising the peritoneum overlying the root of the transverse meso colon. Then the [00:22:00] the middle colic artery and its branches gets readily identified. So when you identify, then we can follow it in one direction or the other to identify the left branch. Now then. If you have a good CT scan, you can identify, you can often see like how far along the middle clic artery as it originates from the SMA. Does it bifurcate? Not always possible to tell super skinny patients, much harder to tell, right? You have to have a little bit of adipose tissue to help you with this. But I think in general principle, what we now want to see is where's this vessel heading on the transverse colon. You'll see one that goes to the left, often that comes off relatively proximally and one that goes more to the right and that's the one we wanna ligate at that level. Once you've done this and sort of connected, we will then we should be able to sort of be in that fused lesser sac plane. That's that fused plane on the right, towards the right side of the lesser sac, right where the transverse meoc colon is [00:23:00] kind of fused as opposed to the left side where we have a very clear lesser sac. But we've not, once we've done that mobilization, we'll be able to readily identify that from the cephalic aspect of the hepato colic ligament and then complete our mobilization that way. So that's kind of how we identify the vessels, which is, look at the. Originating vessels as a way of helping us find the origin of the primary feeding vessel and ligate that there is some controversy as to, you know, what defines a complete lymphadenectomy. And I think this is now where we get into some of the controversy around D two versus D three versus central vascular ligation, complete meso colic excision. So. I think the principles are, we want a complete mesenteric envelope, fa so that in is, can be considered a complete meso, colic, excision, right? If we have that envelope. But that often goes hand in hand with a complete lymphadenectomy, [00:24:00] which some people would advocate. Includes the lymph nodes on the SMV and some pe. Fewer people then still, but still would advocate along the smma SL as well. If there is some controversy as to what is true D three lymph node dissection, but anything to the patient's left hand side of the right side of the vein is the D three distribution, right? So if we have exposed the SMV, we've, we have removed. Some D three level lymph nodes, but, but really the goal here is to ensure that we have a complete D two dissection. So if we ligate on the right side, the reason we take the approach that we do is that it actually is harder to know when you're at the origin of the vessel and in some ways. Potentially more dangerous because you haven't identified the anatomy, right? So you're, we're trying to ligate it where we can't see where the dangerous anatomy is, but if we have identified the SMV, follow the principle that there are no anterior branches. Therefore, [00:25:00] if we're on that perivascular plane, it is a very safe plane, then we can very safely do those ligations. I will, I will just parenthetically say there are people out there who think that we will end up killing patients or really hurting patients. With too much emphasis on some of what I've described. The main concern is along the Gastrocolic trunk. That is probably the area of most unfamiliarity. When I was in training, we learned that as Tiger Country, and the reality is that is probably one of the most critical, you know, areas to address. I don't know how we get through that, you know, in sort of US surgical training, but I do think that. I do think that as we think through some of this and sort of highlighting that you know, the importance of really kind of, you know, being attentive to the anatomy as we embark upon, you know, these operations I think will be key. Because that's how we keep, you know, people more safe. Like, I think the reason why there's risk of hurting people is people sort of hear the CME [00:26:00] concept and they try to do it without understanding the anatomy and so. And I think they will cite the higher rate of vascular injury in the relo trial. And there are, was an early mortality in the in the Copenhagen data that really is probably the best real world observational data. And then early mortality probably was due to some, some risk for operative complications. So, in the learning curve, these are, these are legitimate concerns. So couple questions. I think some people worry that when they get really far over to the patient left that they could accidentally ligate the SMA. Yes. So what are your tricks to make sure that you have the IOC colic pedicle and not the whole SMA and SMV dissected out? Do you dissect distal to the IOC colic coming off to make sure, and then obviously the relationship with the duodenum can be helpful. Yeah. Thanks. So that's a, that is a, it's a good question. The SMA lives. Generally to the left of the SMV [00:27:00] or posterior and left of the SMV. So one can end up injuring it if they're pulling too much right word. Lateral traction on the tissue, on the pedicle right, you can pull it over. So I do think that is a potential risk, but again, I go back to the principle, if we've exposed the vein, we've released some of those tissues, allows the artery to fall back over, and then we wanna make sure that the. There should be a very clear branch coming off of that. So if we're not seeing sort of a, if, let's take the IOC colic as an example. If we're not seeing an artery, a major artery going distal further away after we've isolated the IOC colic, then then, then you have to ask yourself, is this the SMA an another trick? And this is available, whether you're doing robotic or laparoscopic or even open surgery, is that you can do an intraoperative arteriogram with ICG. And so if you do fluorescence [00:28:00] imaging, so you can inject some in, you know, endo, sign in green and then watch the artery fill. And as you do that, you have real time arteriography. So that is a useful adjunct that we use quite a bit in REVE surgery. And where, you know, unfortunately, in fact just just yesterday we were doing an operation where there was tumor that was in a retained vascular stump, right? So the ligation was performed just not proximal enough. And so there was a short segment of the residual middle colic vessel. Those are the tumors that end up invading the pancreatic head or the duodenum, et cetera, right. And become real management problems. And so we can use ICG Arteriography to, so the principle's still the same first we identified in this case. And we can do this minimally invasively, the SMV and then identify the [00:29:00] arterial anatomy. To help clarify the anatomy by using ICG, you know, once we start exposing some of the vessels, both of these techniques using the SMV, we call it the SMV first technique, as well as you know, using ICG and utilizing the SMV to help us with salvage surgery are, have been published in their VI by our group and their videos available for people who are interested. Should everybody be trying to do this kind of surgery or is this an expectation? I don't think so. Right. You know, I think what it kind of points to though are the key principles. And the key principle is we wanna make sure that we're ligating the vessel at its origin so that we complete that lymphadenectomy. While most patients, while most lymph, no metastasis will be pericolic right in that first echelon close to the colon, there are not an insignificant number, probably upwards of 25% that occur between that first echelon. And the feeding vessel origin, right? That's what we wanna [00:30:00] completely resect, and that's what we miss with sort of quote unquote conventional surgery that hasn't identified the origin, the incidence of lymph, no metastasis on the primary root vessels, so-called N three in the Japanese literature, or the central lymph node metastases. These occur. Somewhere in the three to six or 7% range, and the vast majority of them can be identified on preoperative imaging. So we would plan our operation if there's adenopathy there that is concerning, then plan that resection, you know, at the time of surgery. But in the absence of that, it is. It is a complete resection as long as we you know, do that ligation at the origin on the, and, and essentially on the right hand side of that SMV that defines really the origin of the, the feeding vessels on the right, on the left, you know, we define the origin of the feeding vessel as either the IMA or the superior rectal artery, or [00:31:00] the left colic artery, depending on where the tumor's located. Can you discuss you briefly did, but discuss the data specifically for Right. You know, I think people are more aware of the data for left, you know, the, the recommendation here is moderate. The strength of strength of evidence, you know, is probably, is not, you know, these aren't randomized controlled trials, so. What's your best argument for the surgeon who doesn't think they need to do this to convince them to do it? Is it, you know, that that percentage of patients that are gonna recur in those nodes do you think it affects overall survival? And if so why do you think that? Yeah. Well, I think the, the principle behind, you know, unresected disease. Unresected disease will lead to recurrence, right? That's just by definition. So we resect hepatic metastases, you know, as a curative intent operation, and, and we should have the same approach to handling the [00:32:00] primary tumor. Actually, we, in order to do a curative intent operation, all of the regional lymph nodes, so the lymphadenectomy should be complete for the regional distribution. The bowel, of course. And in fact, the bowel resection should be complete if we have, if the, if it involves an adjacent organ, we need to resect all of that on block. You know, that's a sort of a, it is a same general concept. Now there is some literature regarding so-called complete meso colic excision that does include a more extended lymph node dissection to conventional surgery, which is not defined. Conventional surgery not defined. Meaning, that doesn't mean conventional surgery is the same as D two lymphadenectomy a complete D two, right? Because very often in, in conventional surgery, there's no standardization of that operation. That's what these operative standards are designed to help promote is standardization of what we would. Say is sort of the standard, you know, conventional surgery. And [00:33:00] so in studies, of course, you can't randomize patients to conventional surgery versus sort of this extended lymph ectomy or a complete meso colic excision, which I would argue doesn't necessarily mean even an extended lymph ectomy. When we say extended lymphadenectomy, it can start to sound like more aggressive surgery than necessary. I would simply call it complete surgery. But there is some retrospective observational data that clearly demonstrates a survival advantage, both in terms of decreased risk of recurrence and better survival. Now, there this is not without some potential risk. So there is there is potential risk for vascular injury if you don't have proper training. So in Europe, actually, there are a number of programs designed to train surgeons on how to do this operation. In Asia, the right colectomy, which is relegated to junior. The most junior operators in the US is regarded as senior operator operation Because of that vascular anatomy and the importance of handling that in China recently was completed [00:34:00] a randomized trial that compared complete musico excision with central vascular ligation 2D two lymphadenectomy randomization by the same surgeon. You could argue then if the same surgeon was performing both operations, that they did indeed have a complete D two lymphadenectomy, right? It. And so now that's a reasonable comparison. So in this randomized study, there was a slightly higher rate of vascular injury in the. Extended Lymphadenectomy group. Now remember, the control arm was a complete D two. This is what we would say is the complete operation, and there was no signal of an advantage of the more radical re or extended lymphadenectomy, but the long-term outcomes, you know, are awaited. I will tell you parenthetically, there was no benefit in long-term results, but in a certain subgroup there, there was an advantage and it was the stage three patients. And that would be, that would be clearing [00:35:00] out all the lymphatic tissue in front of and behind the SMB all the way over to the SMA, the extended. So, so this, this is the re arc study and they are currently reporting their long-term primary outcomes. And it, one of the controversies of this study is they defined. Experimental arm, which is the extended resection arm as lymphadenectomy to the anterior aspect of the SMA. So quite far over. Yeah. And so, remember we said the risk of lymph node metastasis to these root nodes is less than five to 7%. So. And arguably some of these root node metastases, if they're occurring kind of on the right word of the SMV, we might identify and get them with lymph, with a stand, with a good D two. And so I think it's, it's certainly quite controversial whether or not we need to be that far over. I think the approach that, that we've described, or that I described earlier, was [00:36:00] really an approach to ensure that we have a complete D two lymphadenectomy and we in the process will have, some of the D three level lymph nodes as well. Some people would argue exposure of the SMV constitutes a complete D three lymph node dissection, even the Japanese. I would argue that even the Japanese guidelines or people who are involved in the kins probably wouldn't have consensus on whether you need SMA or SMVs or not. Just to be clear, you know, a lot of these things that we've been discussing are, you know, the, the MD Anderson and Dr. Chang approach. The standard says, you know, proximal vascular ligation at the origin of the primary feeding vessel. How do you understand those terms? Do you think that if you take the artery at the right side of the SMV without necessarily exposing the anterior surface, that still would meet, you know, what you guys described in the textbook? Absolutely. When you were in the room coming up with that wording. [00:37:00] Absolutely. I think that, you know, the idea is to get to the origin, not, you know, not, oh, here's where we think the origin is, because often you can't identify that unless you've seen the anatomy clearly. Right? So the concept is get to the origin. Our approach to utilize SMV is so that we can have a very clear view of those structures, right? It is our way, but there are other ways to achieve the same thing. But this is, this is the way that we've identified to ensure that we have not only a complete resection, but that the resected specimen is impact. As you know, there is a grading system. For even that mesentery, we don't want any holes in it. We don't want, just like there's a grading system for rectal resections, there's a grading system for colon re resections. And while that has not gained as much traction as the grading system for rectal resections or so-called TME completeness, there is a CME completeness or meso colic, you know, envelope. Completeness grade, and again, the [00:38:00] same principles. We wanna ensure that we're not exposing the muscularis in the area of the tumor and that we have that investing envelope is in, is intact. Well, that was fantastic. Thank you very much Dr. Chang. This is a complicated topic and we appreciate you talking us through some of these complex operative steps to help us meet these cancer surgery standards. Thank you. It's, it's been a pleasure. And, and thank you all so much for highlighting these issues. I think you know, highlighting this, these issues will improve outcomes for cancer patients across the country. You know, a high quality operation will do more to improve survival than any adjuvant therapy that we can give. Thanks for inviting me To our audience, thank you again for joining us for our first episode in this series about the operative standards of cancer surgery. Stay tuned for future episodes on the pancreas, melanoma, breast, and other disease sites to come. Thank you.