Rectal cancer is approximately 30% of all of colorectal cancers. In my practice, that incidence is totally reversed. About 70% of my cases are rectal cancer cases, mainly because of the referral pattern. Surgery is the mainstay of therapy of rectal cancer. For all the guidelines, adjuvant therapies, and recommendations that are made in this presentation today, it all assumes that the surgery has been optimal and that the adjuvant therapies are going to be optimal in their outcomes.
I cannot emphasize enough that treating rectal cancer is different than treating colon cancer in terms of the surgery. Rectal cancer is located in the pelvis surrounded by a lot of structures that are either unresectable or have a big impact on a patient's quality of life. You can tell patients that you are going to take out their right colon, their right kidney, or part of their duodenum, and it does not bother them very much. You tell them you are going to take out their bladder or part of their sacrum, and that is a different story.
The crux of the matter is that it is much harder to get significant margins of normal tissue around rectal tumors than it is for colon tumors. For that reason, the local recurrence rate is higher. That is the reason that the other locoregional treatment that we use is radiation therapy.
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Surgery is the primary modality for curative treatment. It is the only therapy required for early stage disease. For the most part, we mean stage I rectal cancer where you have a T1 or a T2 tumor that is node negative.
Certainly, there are tremendous advantages to the avoidance of chemoradiation therapy in this disease and not everyone with rectal cancer should receive chemotherapy and radiation. In fact, you should look very hard to find patients who are not going to benefit from this. Adjuvant therapy increases the likelihood of cure in cases that are surgically treated in the best way that we can in order for the adjuvant therapies to be optimal.
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The principles are very straightforward. They are easy to say and often difficult to accomplish. There is removal of the primary tumor with adequate margins. This does not just mean the distal margin—the margin toward the anal canal—it also means the margin around the outside of the tumor, often referred to as the circumferential or radial margin.
It is very important to treat the draining lymphatics. Probably the biggest advance in rectal cancer surgery in the recent past has been the recognition of total mesorectal excision (TME) as a way of reducing local recurrence within the pelvis; to a large extent, that is what treatment of the draining lymphatics means. It was known long ago that lymphatic drainage from a rectal tumor is upward in the abdomen toward the root of the inferior mesenteric artery. That fact helps to define why we do the surgery that we do today.
Last but not least, especially from the patient point of view, is restoration of organ integrity, if possible. The great majority of patients with rectal cancer are going to have sphincter preservation with acceptable bowel function.
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The first thing we need to do is talk about defining the rectum. For our purposes in the National Comprehensive Cancer Network (NCCN), we have chosen to say that the colon is greater than 12 cm from the anal verge by rigid proctoscopy. The rectum is less than that. Why is that important? Because the local recurrence rate for lesions above that level is much lower than it is for lesions that are below that level.
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Another way of looking at it is how the rectum has been defined in clinical trials that we use for therapeutic decision making. In many cases, this is defined in variable ways: for example, below the sacral promontory on lateral barium enema in this study with lesions below that level having this local recurrence rate, local recurrence rate below that level being 27%. In the Dutch trial in 2001, they used the level of 15 cm from the anal verge or S1-2 with similar findings of a higher local recurrence rate in the lower lesions. In this study, the level was 16 cm to the inferior margin of the tumor with similar results.
So we have chosen a very conservative definition, and we feel that that is consistent with the clinical trial data and is reproducible in terms of rigid proctoscopy. Of course, this should be done by the surgeon who is responsible for the case. One should not simply accept a flexible endoscopy report from a gastroenterologist or non-surgeon.
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One of the things that has been used in the past to define the rectum is the location of the peritoneal reflection. One thing that is very clear to those who routinely operate in the pelvis is that the peritoneal reflection is not a fixed landmark. It varies widely, it is often much higher in men and lower in women, and, in fact, in elderly women it can be almost at the top of the anal canal. One needs to keep that in mind when one is referred a case where this is the way that the rectum is defined.
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The recommendation for workup at clinical presentation for a rectal lesion from the NCCN guidelines for a mass in the rectum with an invasive cancer is for pathology review. A complete examination of the colon to rule out any synchronous polyps or other tumors is recommended, as well as marking of the site if the patient has had a polypectomy.
In terms of removal of these tumors, if it was a single specimen removal with favorable histologic features and clear margins, T1, we feel that patients can go onto observation or adjuvant therapy can be considered.
For patients who have fragmented specimens, which is frequently the case, and the margin cannot be assessed in a fragmented specimen, or there are unfavorable histologic features, we recommend a more definitive surgical management.
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If the lesion is T1 or T2, we recommend going on to transabdominal resection and then observation if the patient is lymph node-negative. For patients with high-risk rectal cancers, either those that are through the bowel wall or that have positive lymph nodes, those patients should go on to appropriate adjuvant treatment. For some patients, transanal excision can be considered if there is favorable histology, negative margins, and the patient is fully aware of the risks of that approach.
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In cases where transanal excision is done and accepted as definitive surgical treatment and the margins are negative, patients can go on to 5-fluorouracil (5-FU)-based treatment with chemotherapy to be considered upon discussion with their medical oncologist.
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What are some of the essentials of an adequate local excision? This is something that you really need to look at when you are evaluating patients that are referred to you. It needs to be full thickness: by that, we mean perpendicularly through the bowel wall into the perirectal fat. The deep margin and the mucosal margins need to be free of tumor, and the surgeon should pin out the specimen specifically and take it to the pathologist themselves. That is absolutely critical to avoid problems with the pathology.
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There are two major ways to look at local excision as a viable treatment. One is technical, and the other is biologic. The technical reasons are for local excision. It is a small tumor and very superficial. Those are technical reasons in terms of being able to control the specimen as you do the full thickness excision and then be able to close the rectal defect. If you cannot reach the lesion, it generally is a poor candidate for transanal excision based on technical factors.
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Secondly, there are biological issues in local excision. Lymphovascular invasion usually is a sign that you should not be doing local excision, because there is a very high local recurrence rate in rectal tumors with lymphovascular invasion that are locally excised.
Similarly, poor differentiation is another factor in high rates of local recurrence if you choose to do local excision. If you do less than a full thickness excision, there is a high local recurrence rate. So there are really two factors to keep in mind in selecting patients for local excision: technical factors and biologic factors.
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Chris Willet looked at local excisions done for early rectal cancer and compared them with the results of abdominal perineal resection (APR). When those previously mentioned factors were not favorable, the local excision patients, even for these early rectal cancers, had a local recurrence rate of 33%; whereas for these early tumors, the local recurrence rate was 9% to 11%, even in the unfavorable cases. I think that tells us a lot about those selection factors and how important it is that they be all in line before you choose that as definitive surgical treatment.
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Why does the depth of penetration matter? As tumors go through the intestinal wall and become T3 cancers, the risk of nodal metastases reaches a very high rate. If you look at the risk of nodal metastases from APR data, before we did any preoperative chemoradiation, this was the risk of nodal metastases for T1, T2, and T3 tumors. When you look at a series from the same era where local excision was done for T1, T2, and T3 tumors, the local recurrence rate mirrors that risk of nodal metastases. The problem with local excision is that it does not address the risk of nodal metastases.
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One additional issue about local excision is that, over a series of papers where local excision and postoperative radiotherapy were used in order to try to address the problem of residual cancer within the mesorectum, it showed that the local recurrence