Sabiston Colorectal Cancer

Question 1

Lynch Syndrome

Answer 1

• Genes (MLH1, MSH2, MSH6, PMS2, EpCAM)
• ## Mutations in MLH1 and MSH2 account for up to 90% of patients with Lynch syndrome

Question 2

Amsterdam II citeria.

Answer 2

• Three or more relatives with hereditary nonpolyposis colorectal cancer–associated cancer (colorectal cancer or cancer of the endometrium, small bowel, ureter, or renal pelvis) plus all of the following:

1. One affected patient is a first-degree relative of the other two.
2. Two or more successive generations are affected.
3. Cancer in one or more affected relatives is diagnosed before the age of 50 years.
4. Familial adenomatous polyposis is excluded.
5. Pathologic diagnosis of cancer is verified.

Question 3

What Mutation Goes Against Lynch Syndrome

Answer 3

The presence of BRAF mutations in an MSI CRC is evidence against the presence of Lynch syndrome.

Question 4

Lifetime Risk For CRC in Lynch

Answer 4

The estimated lifetime risk for CRC is 70% for men and 40% for women.

Lynch syndrome–associated CRCs show a predilection for the right colon as compared to sporadic CRC

Question 5

Regarding Adenomas in Lynch

Answer 5

Compared with patients with AFAP or MAP, patients with Lynch syndrome develop few colorectal adenomas by the age of 50 years (usually fewer than three adenomas).

Question 6

Histologic features in Lynch

Answer 6

Histologic features showing

• poor differentiation
• mucinous or signet-ring cell histology
• tumor-infiltrating lymphocytes
• lymphoid host response are common.

Question 7

Most common extracolonic cancer in Lynch

Answer 7

Endometrial adenocarcinoma is the most common extracolonic cancer (lifetime risk of 32%–45%).

Ovarian, gastric, small bowel, urinary tract, brain, and pancreas cancers

Question 8

in the following situations should be tested for MSI

Answer 8

1. Colorectal cancer diagnosed in a patient before age 50.
2. Presence of synchronous/metachronous colorectal or other hereditary nonpolyposis colorectal cancer (HNPCC)–related tumors

(including endometrial, stomach, ovarian, pancreas, ureter and renal pelvis, biliary tract, brain (usually glioblastoma), sebaceous gland adenomas and keratoacanthomas, and carcinoma of the small bowel), regardless of age.

3. Colorectal cancer with the MSI histology
   (defined by the presence of tumor-infiltrating lymphocytes, Crohn-like lymphocytic reaction, mucinous/signet-ring differentiation, or medullary growth pattern) diagnosed in a patient before age 60.
4. Colorectal cancer diagnosed in at least one first-degree relative with an HNPCC-related tumor in which one cancer was diagnosed before age 50.
5. Colorectal cancer diagnosed in at least two first- or second-degree relatives with HNPCC-related tumors, regardless of age.

Question 9

When Screening for CRC

Answer 9

• Screening for CRC by colonoscopy is recommended in persons at risk
  (first-degree relatives of known MMR gene mutation carriers who have not had genetic testing)
  or those affected with Lynch syndrome every 1 to 2 years,
• beginning at 20 to 25 years of age or 2 to 5 years before the youngest age of diagnosis of CRC in the family if diagnosed before age 25 years

Question 10

For MMR germline mutation–positive patients Screening

Answer 10

• annual colonoscopy
• pelvic examination and endometrial sampling annually starting at age 30 to 35 years.
• screening of ovarian cancer should be offered beginning at the same age.
• Hysterectomy and bilateral salpingo-oophorectomy should be offered to women with Lynch syndrome undergoing colectomy, in all women over age 40 years or who have finished childbearing.
• Screening for gastric cancer EGD with gastric biopsy of the antrum at 30 to 35 years, and subsequent surveillance every 2 to 3 years can be considered based on individual patient risk factors.
• Screening for cancer of the urinary tract should be considered for persons at risk for or affected with Lynch syndrome, with urinalysis annually starting at age 30 to 35 years.

Question 11

For Lynch , total or segmental Resection

Answer 11

• The cumulative risk of metachronous CRC in patients with segmental colectomy is

16% at 10 years
41% at 20 years
62% at 30 years.

there is superior cancer risk reduction with total colectomy for the treatment of colon cancer in the setting of Lynch syndrome, and total abdominal colectomy with IRA is the preferred treatment for most patients.

For patients with Lynch syndrome and rectal cancer, the rectal cancer should be treated based on standard oncologic principles, as in sporadic rectal cancer

Consideration for less extensive surgery should be given in patients older than 60 to 65 years and those with underlying sphincter dysfunction. Annual colonoscopy should be performed after segmental resection of colon cancer.

Question 12

fused PET/CT scans are usually not used for initial staging for CRC, When its used ?

Answer 12

fused PET/CT scans are usually not used for initial staging but may be used in patients with

contrast allergy/renal failure or in equivocal cases

Question 13

Prognostic Factors

Answer 13

• serum carcinoembryonic antigen (CEA) levels,
• the presence of tumor deposits within the lymph drainage area of a cancer
• (lymphovascular and perineural invasion respectfully)

The histologic grade of the tumor (low grade vs. high grade)

histologic subtypes such as mucinous and signet ring adenocarcinomas, which are usually more aggressive and carry a worse prognosis.

The circumferential resection margin should be reported by the pathologist, as well as the proximal and distal margin status and in rectal cancer, the completeness of the mesorectal excision.

Question 14

molecular markers for somatic and germline mutations are investigated, such as

Answer 14

MSI, KRAS, BRAF, and NRAS mutations

which can help in both prognosis and treatment planning

Question 15

anatomic vascular landmarks

Answer 15

• The ileocolic pedicle originates from the superior mesenteric vessels just caudal to the second portion of the duodenum.
• The middle colic vessels originate from the superior mesenteric vessels at the level of the inferior margin of the pancreas.
• The inferior mesenteric vein can be easily identified at the level of the ligament of Treitz (Fig. 52.64).
• The IMA originates from the aorta, 2 to 3 cm caudal from the area where the IMV is identified; its origin is surrounded by the mesenteric and hypogastric nervous plexus.
• The left colic artery originates about 2 cm distally to the origin of the IMA.

Question 16

The vascular supply of the colon, which is mobilized and utilized for the anastomosis, relies on

Answer 16

marginal vessels located in the mesocolon

Question 17

Right-Sided Tumors Steps ( cecum and ascending colon )

Answer 17

• detachment of the right abdominal side-wall attachment
• the vascular pedicles are ligated once the right colon has been fully mobilized
• division of the ileocecal pedicle at its origin from the superior mesenteric vessels and division of the right colic vessels , and right branch of the middle colic vessels is divided
• lymphatic tissue that surrounds the superior mesenteric vein can be removed en bloc
• terminal ileum is divided with a stapler 5 to 6 cm from the ileocecal valve and the transverse colon at the junction between its mid and proximal third.
• omentum has to be removed en bloc, together with the gastrocolic ligament that is divided along the gastroepiploic arcade
• extracted through a Pfannenstiel incision that has fewer short- and long-term complications
• ileotransverse anastomosis

In laparoscopy or robotics, the colectomy is usually performed with a medial to lateral approach with initial vascular control and then detachment from the abdominal side wall.

Question 18

An intracorporeal anastomosis vs Extracorporeal

Answer 18

An intracorporeal anastomosis seems to bring advantages in terms of
- fewer anastomotic complications (leaks and twists)
- faster recovery of bowel function and discharge

Question 19

Tumors of the Transverse Colon

Answer 19

• Right extended colectomy
• middle colic vessels are divided at their origin at the level of the inferior margin of the pancreatic neck
• ileocolic anastomosis is made at the distal third of the transverse colon

Question 20

Tumors of the Splenic Flexure

Answer 20

• extended right-sided resection, to encompass the splenic flexure, Or resection of the splenic flexure alone
• The inferior mesenteric vein is ligated at the level of the ligament of Treitz and the left colic artery is divided at its origin from the IMA and the specimen is taken en bloc with the omentum
• anastomosis between the transverse and the descending colon.

In selected cases, where the mesentery of the colon is thick and the colon is short, this colocolic anastomosis can compress and obstruct the duodenum at the ligament of Treitz. In these cases, extended right hemicolectomy with ileo-descending anastomosis is preferable.

Question 21

Left-Sided Tumors

Answer 21

• Left hemicolectomy
• high ligation of the IMA at its origin
• IMA can also be ligated 2 to 3 cm more distally without compromising the oncologic outcome but lowering the risk of injuring the mesenteric and hypogastric nervous plexus
• inferior mesenteric vein is divided
• splenic flexure must be fully mobilized, coloepiploic detachment, detachment of the mesocolon of the splenic flexure and distal transverse from the pancreas, and left abdominal gutter detachment.
• anastomosis without tension between the left colon and the proximal rectum below the rectosigmoid junction
• Restoration of bowel continuity is made with a transanal circular stapler that should have a caliber of about 3 cm

Question 22

A damage of the hypogastric nervous plexus carries the risk of

Answer 22

genitourinary complications, including retrograde ejaculation in males, bladder dysfunction, and vaginal dryness in women.

Question 23

Management of sigmoid and left colon obstructions

Answer 23

A segmental resection of the primary tumor is typically performed.

If the proximal large bowel has perforated or is showing signs of ischemia, a subtotal colectomy is completed

Current evidence supports the option of a primary anastomosis in appropriate patients who are hemodynamically stable

A proximal diverting stoma may also be exteriorized combined with a primary anastomosis. This does not reduce the anastomotic leak rate but may decrease the quantity of leaks requiring reoperation

Question 24

Stent in Left Obstruction

Answer 24

Stenting has been shown to permit
higher rates of primary anastomosis
decreased wound infections
and a higher rate of completion of surgery laparoscopically.

Stenting is contraindicated in suspected ischemic or perforated bowel.

Question 25

Treatment of right-sided obstructions

Answer 25

oncologic segmental resection. In most cases, a primary ileocolic anastomosis can be performed safely, but for patients with a high risk of anastomotic failure, a diverting stoma can be exteriorized.