Colon Cancer Basic Science 9/21/05

Colon and rectal neoplasms are characterized by: Consist of the third most common site of new cancer cases and deaths in both genders in the US. The lifetime risk of developing colorectal cancer in this country is 10%. Over 90% of cases occur after the age of 50. Colorectal cancer occurs in 3 forms: sporadic, hereditary and familial. In the sporadic form, there is typically an absence of family history, it tends to affect the older population, and although the specific mutation is present in all cells, only colon or rectal cells are affected.

Colon and rectal neoplasms are characterized by: Consist of the third most common site of new cancer cases and deaths in both genders in the US. T The lifetime risk of developing colorectal cancer in this country is 10%. F, 6% Over 90% of cases occur after the age of 50. T Colorectal cancer occurs in 3 forms: sporadic, hereditary and familial. T In the sporadic form, there is typically an absence of family history, it tends to affect the older population, and although the specific mutation is present in all cells, only colon or rectal cells are affected. F, genetic mutations associated with the cancer are limited to the tumor itself.

All the following concerning cancers in the left colon are true except: Are often obstructive on presentation. Can present as LLQ pain, fever, and obstructive symptoms mimicking diverticulitis. If bleeding is present, is more likely to present as bright red blood per rectum. Represent a majority (>80%) of all colon cancers.

All the following concerning cancers in the left colon are true except: Are often obstructive on presentation. T Can present as LLQ pain, fever, and obstructive symptoms mimicking diverticulitis. T If bleeding is present, is more likely to present as bright red blood per rectum. T, although a majority of colon cancers present as occult. Represent a majority (>80%) of all colon cancers. F, at least half of all colon cancers are located proximal to the area visualized by a flex sigmoidoscopy, and the incidence of right colon cancers is rising.

All the following concerning the surgical approach to colon cancer are true except: Ileocolic anastamosis after colon resection for cancer is generally avoided in patients presenting with complete obstruction. Non-obstructing patients should undergo metastatic w/u including PE, CXR, LFT’s, CEA, and abdominal CT. The presence of hepatic metastases generally precludes colonic resection of the tumor. The proximal sigmoid is often excluded from an anastamosis due to poor blood supply and frequent involvement with diverticular disease.

All the following concerning the surgical approach to colon cancer are true except: Ileocolic anastomosis after colon resection for cancer is generally avoided in patients presenting with complete obstruction. T due to high risk of leak. Non-obstructing patients should undergo metastatic w/u including PE, CXR, LFT’s, CEA, and abdominal CT. T The presence of hepatic metastases generally precludes colonic resection of the tumor. F, excision of the primary cancer can provide significant palliation. The proximal sigmoid is often excluded from an anastomosis due to poor blood supply and frequent involvement with diverticular disease. T

Which of the following concerning colorectal cancer staging are correct? Stage 1 consists of tumors invading the submucosa (T1) or muscularis (T2) without nodal disease (N0). Lymph node metastases automatically classifies a lesion as stage 4. 5 year survival for stage 1 and 2 cancers is as high as 75% and 50% respectively with appropriate resection. All stages of cancer benefit from adjuvant chemotherapy such as 5-FU and Leukovorin after curative resection.

Which of the following concerning colorectal cancer staging are correct? Stage 1 consists of tumors invading the submucosa (T1) or muscularis (T2) without nodal disease (N0).T Lymph node metastases automatically classifies a lesion as stage 4. F, Stages 3 and 4 both include nodal metastases with 4 having distant metastases. 5 year survival for stage 1 and 2 cancers is as high as 75% and 50% respectively with appropriate resection. F, 90% and 75% respectively, which are improved with adjuvant chemotherapy. All stages of cancer benefit from adjuvant chemotherapy such as 5-FU and Leukovorin after curative resection. F, stage 3 clearly benefits with stages 1 and 2 showing no clear benefit.(controversial)

Local excision is considered appropriate therapy for rectal CA under which of the following conditions? Applies to small cancers of the distal rectum that have not penetrated the muscularis. The tumor is mobile and less than 10cm in diameter. Less than 40% of the rectal wall circumference may be involved. Lesions must be within 2cm of the anal verge. Lesions are classified as stage 1 or 2. Is appropriate for palliation in patients with advanced cancer and severe co-morbid disease. Adequate clear margins are attainable.

Local excision is considered appropriate therapy for rectal CA under which of the following conditions? Applies to small cancers of the distal rectum that have not penetrated the muscularis. T The tumor is mobile and less than 10cm in diameter. F, mobile and less than 4cm. Less than 40% of the rectal wall circumference may be involved. T Lesions must be within 2cm of the anal verge. F, must be within 6cm of anal verge. Lesions are classified as stage 1 or 2. F, applicable to Stage 1 (T1 and T2) only. Is appropriate for palliation in patients with advanced cancer and severe co-morbid disease. T Adequate clear margins are attainable. T

The use of fulguration in rectal lesions is significantly limited by: Destroys the tumor by creating an eschar that extends into perirectal fat and thus destroys the tumor and rectal wall. Can only be used for lesions located below the peritoneal reflection. Can be complicated by significant postoperative fevers and bleeding up to 10days out. By virtue of its mechanism of action cannot produce a specimen for pathologic evaluation. Is used in patients with prohibitive operative risk or those with limited life expectancy.

The use of fulguration in rectal lesions is significantly limited by: Destroys the tumor by creating an eschar that extends into perirectal fat and thus destroys the tumor and rectal wall. T Can only be used for lesions located below the peritoneal reflection. T Can be complicated by significant postoperative fevers and bleeding up to 10 days out. T By virtue of its mechanism of action cannot produce a specimen for pathologic evaluation. T Is used in patients with prohibitive operative risk or those with limited life expectancy. T