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Colorectal Cancer
133,500 new cancers of the colon and rectum are diagnosed annually, thus, the lifetime
probability of an individual developing colorectal cancer is approximately 5 to 6 percent.
It is further estimated that 54,900 people will die of their cancer each year, making
colorectal cancer the second leading cause of cancer death in this country. There seems to
have been a decrease in the incidence and mortality in the last decade, which suggests
greater awareness of the disease and improved detection and prevention.
Epidemiology and Etiology
It is generally accepted that the majority of colorectal cancers arise in a preexisting
adenoma and that the risk for cancer increases within the adenoma as the histology of the
polyp becomes more villous and the size of the polyp becomes larger. This adenoma to
cancer sequence is the basis behind routine colonoscopy with polypectomy as a means to
prevent colon cancer. Other factors that are felt to protect against the development of
colorectal cancer include a high vegetable fiber intake and Calcium supplementation. In
addition, an active life and exposure to sunlight may offer some protection. Lifestyle
components that may increase the risk of colon cancer include eating a diet high in fat,
alcoholism, and certain styles of food preparation such as deep frying, barbecuing, and
smoking.
A family history of colorectal cancer markedly increases the risk of colorectal cancer or
adenomas in an individual. Other risk factors for the development of colon cancer include
inflammatory bowel disease, a personal history of colon polyps or colon cancer, and a
personal history of breast cancer.
Prognosis:
Staging
When evaluating prognostic factors, staging remains the most accurate predictor of
patient outcome.
T stage
The depth of colon wall invasion greatly affects the patient's prognosis. Tumor confined
to the colonic submucosa (T1) will be associated with metastases in less than 10 %
percent of cases. When the muscularis propria is penetrated (T2), the risk of metastases
increases to 10 to 20 percent. Full-thickness penetration into the perirectal fat yields a
metastatic rate of 33 to 58 percent.
N Stage
Lymph node metastases in colon cancer patients in an ominous finding which often has a
significant negative impact on survival. The number of positive lymph nodes correlates
with patient survival. Patients with one to four positive lymph nodes (N1) have survival
rates of 50 to 55 percent. The presence of five or more positive lymph nodes (N2) drops
survival rates to 22 to 28 percent. Because nodal status is so important to the prognosis of
cancer, recent guidelines suggest that the optimal surgical resection include at least 12
lymph nodes for pathological evaluation.
Metastatic Cancer (Stage IV)
The most common sites of distant metastases were found to be the liver and lungs. The
prognosis for stage IV patients is poor, with five-year survival rates around 5 percent.
Other Predictors of outcome
The histology of the tumor seems to predict outcome. Tumors with poor differentiation,
mucin production, and lymphovascular invasion all carry a worse prognosis. Young age
at diagnosis was thought to carry a worse prognosis, but not when compared stage for
stage. The same holds true for gender and race. Patients who are young or are of nonCaucasian race are usually diagnosed at a later stage and therefore tend to have a worse
prognosis.
Colon Cancer Cases at Methodist Hospital of Dallas in 2006
There were 99 cases of colon cancer (42 male, 57 female) placed in the tumor registry at
MMC in 2006. (Rectal cancers are not included in this discussion as they behave
differently than cancers of the colon and recto-sigmoid junction). Of these cases, 86 were
diagnosed and began treatment at MMC while the other 13 represented those with
recurrent disease as they were diagnosed and underwent the first round of treatment at
outside facilities.
Demographics:
The majority of colon cancer cases occur in patients over the age of 50 with fewer than
10% of cases diagnosed at an age younger than 50. At MMC, 18.7% of the cases (16
patients) of colon cancer were diagnosed in patients younger than 50. Furthermore, colon
cancer in the octogenarian also represents a special age group and at MMC 16.3% (14
patients) of the cases were over the age of 80. When race was considered, the majority of
patients diagnosed were African American (45.3%) followed by Caucasian (36.1%),
Hispanic (16.3%) and asian (2.3%).
Stage and Treatment:
As mentioned in the introduction, stage of disease is the most accurate predictor of
outcome. Of 83 analytical cases in 2006, 1 patient was diagnosed at stage 0, 15 at stage I,
18 at stage II, 33 at stage III, and 16 at stage IV. The remaining 3 cases left the system
with an unknown stage of disease
The treatment for stage 0, stage I, and stage II disease is often surgery alone. The
exception to this includes patients who have some complicating factor such as aggressive
histology, obstructive symptoms, or perforation. In the MMC database, All Stage 0 and
Stage I patients were treated with surgery only. There was one patient with Stage II
disease that received chemotherapy in addition to surgery due to a complicating factor of
their disease. Traditionally, all stage III patients should be offered chemotherapy as it has
been shown to improve long term survival for stage III disease. At MMC, 27 patients
with stage III disease received chemotherapy in addition to surgery, 4 patients had
chemotherapy held due to comorbid disease, 1 patient refused chemotherapy, at there is
no record of chemotherapy in the remaining patient. The treatment of stage IV disease is
often tailored appropriately based on the patients functional status, extent of disease, and
resectabilty of the tumor. At MMC 6 Patients with stage IV disease received both
chemotherapy and surgery, 5 received surgery alone, 2 received chemotherapy alone, and
3 were referred to hospice and did not receive any specific treatment.
Survival:
Nation wide, the overall 5 year survival for stage 0, I, and II disease ranges from 80%,
76%, and 63% compared to 50%, 69%, and 44% respectively for the MDMC patients. As
expected, the survival significantly drops with metastatic disease, such that nation wide
stage III disease has a five year survival of 52% and stage IV survival at five years is only
6%. At MDMC the five year survival at stage III and IV are 44% and 12% respectively.
(insert table with comparative data here)
Conclusion:
Colon cancer is a common malignancy. Patient survival is highly dependant on stage at
the initial diagnosis. The patient outcomes at MDMC follow the same trend as the nation
wide data, but the true comparison is difficult to make in light of the small number of
patients available for comparison.