Colon and Rectum. Anatomic Considerations and Patterns of Spread. Rectum . 12 to 15 cm in length from the rectosigmoid junction to the puborectalis ring upper third middle third (posterior border of the rectouterine pouch or rectovesical space) lowest third no serosal barrier.
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bowel habits, weakness, intermittent abdominal pain, nausea, and vomiting.
The persistence of such symptoms as well as any evidence of iron deficiency anemia should be investigated
exophytic ,iron deficiency anemia
deeply invasive, annular, and accompanied by obstruction and rectal bleeding
FIGURE 58.1. Idealized depiction of peritoneal relationships in the colon and rectum. The transverse and sigmoid colon are intraperitoneal, with a complete peritoneal covering (serosa) and mesentery. The ascending and descending colon are retroperitoneal, lack a true mesentery, and usually do not have a peritoneal covering posteriorly or laterally. The upper rectum begins above the peritoneal reflection and has peritoneum anteriorly and laterally. The lower half to two thirds of the rectum is below the peritoneal reflection (infraperitoneal).
The goal of screening is to detect preinvasive polyps or early invasive cancer. The presence of polyps increases the risk for cancer to approximately 15%. Data from programs in which proctoscopy is performed annually suggest that routinely scheduled polypectomy reduces the development of subsequent bowel cancer by 80% or more .
The American Cancer Society has recommended screening should begin at age 50 in the average risk patient by either:
Although screening methods can detect colorectal cancer at an early stage, <40% of patients are diagnosed with early disease, likely reflecting low rates of disease awareness as well as the infrequency of screening in eligible candidates
Direct invasion in T4 includes invasion of other segments of the colorectum by way of the serosa; for example, invasion of the sigmoid by a carcinoma of the cecum. Tumor that is adherent to other organs or structures, macroscopically, is classified as T4. However, if no tumor is present in the adhesion, microscopically, the classification should be pT3
average 5-year survival
In summary, local failure occurs in patients with colonic tumors where there are anatomic constraints on radial resection margins, including tumors adherent to or invading adjacent structures.
To summarize, these studies have suggested that operative bed failures in high-risk patients undergoing resection alone are at least 30%, and that the risk of local failure is reduced by the administration of adjuvant radiation therapy.
FIGURE 58.2. Idealized postoperative anteroposterior-posteroanterior irradiation fields of extrapelvic colon cancer (tumor bed and nodal regions). If treated preoperatively, lateral fields could be added based on imaging with computed tomography of the abdomen and colon radiograph. A: Para-aortic nodes are at risk, in addition to tumor bed, due to tumor adherence to posterior abdominal wall with descending colon cancer. B: External and common iliac nodes are at risk, in addition to tumor bed, from proximal ascending colon cancer.
local control rates in patients undergoing intraoperative boost were 89% compared to 18% undergoing external irradiation alone
margin negative resection (66%)
microscopic residual (47%)
gross residual (23%).
A study from the University of Florida of patients with locally advanced but completely resected colon cancers receiving adjuvant radiation reported a local control rate of 88%, similar to the 90% reported at the Mayo Clinic in patients who had completely resected tumors.
The 5-year rate of local control was 96% for patients receiving 50 to 55 Gy versus 76% for patients receiving <50 Gy
To assess whether the addition of radiation therapy to adjuvant chemotherapy would result in superior survival and local regional failure rates in resected, high-risk colon cancer patients, the U.S. Intergroup initiated a randomized prospective trial in 1992 (103). In this trial, patients with resected colon cancer were randomized to postoperative irradiation with 5-FU and levamisole or 5-FU and levamisole alone. Eligibility criteria included margin negative tumors with adherence to or invasion of surrounding structures (i.e., T4N0 or N+ disease, excluding peritoneal invasion) or tumors arising in the ascending or descending colon with metastatic regional nodes (T3N+). Patients were randomized to receive (a) weekly 5-FU combined with levamisole for 12 months' duration or (b) 5-FU and levamisole for 12 months with combined radiation therapy and chemotherapy beginning 1 month after the first 5-FU administration. The recommended total radiation dose was 45 Gy in 25 fractions over 5 weeks with an optional 5.4 Gy boost.
11% receiving IOERT plus EBRT versus 82% EBRT only
76% for patients receiving IOERT 26% for patients receiving EBRT alone]
45 Gy in 25 fractions of 1.8 Gy per fraction (primary tumor and at-risk tissues)
Reduced fields to 50 Gy
T4 tumors( a total dose of 54 to 60 Gy)
Any treatment beyond 50 Gy mandates exclusion of all small bowel from the field.
primary tumor site :with a 4- to 5-cm margin proximally and distally with 3- to 4-cm margin medially and laterally to cover areas of potential residual disease.
FIGURE 58.3. Idealized multiple-field preoperative or postoperative irradiation technique for a sigmoid colon cancer adherent to the bladder. Solid lines, large field; interrupted lines, boost field. A: Anteroposterior-posteroanterior. B: Paired laterals
CHRT →S± IOERT+CHT
A similar approach would be reasonable for patients with locally recurrent cancers or with regional nodal relapse
The proximal and distal rectum have historically been defined by the level at which the peritoneum is reflected along the anterior surface of the rectum (usually at the level of S3)
Tumor mobility remains a key factor in both choice and outcome of treatment
They are all less accurate in predicting response after neoadjuvant therapy with high rates of false positivity and should be interpreted with caution in this setting
Distal intramural spread of tumor is rare beyond 1.5 cm, and, therefore, a 2-cm distal margin is currently considered acceptable, except in lesions that are poorly differentiated or widely metastatic
with 5-FU (1,000 mg for meter squared on days 1 to 3 and 29 to 31)
a 25% local failure rate
40% to 50% overall survival,
local failure rate of 10% to 15%
overall survival rate of 50% to 60%.
5-FU/LV showed better relapse-free survival and disease-free survival but not overall survival as compared to MOF.
the combined use of radiation and chemotherapy is more effective than postoperative radiation alone, with a greater potential for improved survival, and is recommended.
nausea, vomiting, diarrhea , stomatitis with mucosal ulceration , hematological toxicity
diarrhea, hand/foot syndrome ,Chronic bowel injury (25% )
rectal urgency with frequent bowel movements
The initial CTV should include macroscopic disease with an approximately 2-cm margin in mesentery and within the course of the large bowel(the initial CTV should include rectal mesentery and nodal regions at risk)
Ongoing phase III trials in the United States and Europe are evaluating capecitabine and oxaliplatin delivered neoadjuvantly with radiation therapy
Doses of 46 Gy or 50 Gy were more effective than 40 Gy, but there was no difference between 46 or 50 Gy. Similar results have been reported from other studies as well.
FIGURE 58.5. A: AP portal of patient with T4 rectal cancer. B: Lateral portal of a patient with T4 rectal cancer.
less than T4 disease
adequate margins >1 cm
Ten to 12.5 Gy for complete resection
12.5 to 15 Gy for microscopic residual
17.5 to 20 Gy for gross residual disease.