30 - Colon & Rectal Cancer Flashcards
1
Q
Colorectal cancer risk factors
A
- Risk of developing colorectal cancers usually begins at age 40 and increases w/ age (mean age at presentation = 70 y/o)
- Risk factors = age, family hx, alcohol intake, diet (high in red meats and processed meats, low in fresh fruits and vegetables), smoking, obesity, IBD
2
Q
Pathophysiology of colon and rectal cancer
A
- More than 95% of primary colorectal cancers are adenocarcinomas (tend to be more responsive to chemotherapy and radiation)
- Colon cancer 3x as common as rectal cancer
- Rectal cancer defined as arising below the peritoneal reflection or < 12 cm from the anal verge
- Colorectal adenocarcinomas tend to remain superficial for a long time, slowly invading the deeper layers of the intestinal wall
- As lesion progresses, there is extension through the bowel wall into the pericolonic fat
3
Q
Signs and sx of colon and rectal cancer
A
- Change in bowel habits
- Tenesmus (continual or recurrent urge to vacate the bowels)
- Diarrhea or constipation
- Blood in stool
- Narrow stools
- Abdominal discomfort and gas pains
- Weight loss
4
Q
Screening and staging of colon and rectal cancer
A
- Recommend continuous screening b/c if the cancer is caught at the early stages there is a much greater chance of survival and lower risk of recurrence
- Stool-blood guaiac test detects presence of blood in the stools
- Sigmoidoscopy (useful visualizing sigmoid colon as well as for taking a biopsy specimen)
- Barium enema (high false negatives possible, thus should be reserved as complement to a scope)
- Colonoscopy
- Carcinoembryonic antigen (CEA) -> not 100% specific, so elevation can be present w/ no colorectal cancer; useful as a marker to find out if therapy is working in diagnosed cancer; should normalize after surgery once cancer is removed
5
Q
Benefits of screening for colorectal cancer
A
- Effective to detect pre-cancerous, early stage or small cancers among people who don’t show signs or sx of cancer
- Decreases the px risk from dying of cancer
- Canadian guidelines call for all people age 50 and older to be evaluated annually or biennially w/ fecal occult blood testing (FOBT) unless pt is at high risk for colorectal cancer
6
Q
Tx options for colorectal cancer
A
- Surgery -> primary curative procedure for px w/ stage 1-3 disease; surgical resection of the bowel (ex: hemicolectomy or abdominoperineal resection)
- Resection of isolated liver and/or lung metastases
- Radiation
- Rectal carcinomas are associated w/ a local recurrence rate much higher than colon cancers
- Adjuvant radiation to the tumour bed, as well as the surgically inaccessible areas of tissue has been shown to decrease local recurrence
- Additionally, radiation can be used for palliation of sx
7
Q
Staging of colorectal cancer
A
- Stage 1 = local disease, no invasion of muscular mucosa
- Stage 2 = invasion of muscular mucosa, no extracolonic spread
- Stage 3 = lymph node involvement
- Stage 4 = metastatic disease
- Sites of metastases = liver, lung, bone
8
Q
When is chemotherapy used for colorectal cancer?
A
- Used in adjuvant setting after surgical resection of stage 2 and 3 cancer
- Despite the high rate of resectability, almost ½ of all px w/ colorectal cancer will recur b/c of residual disease not apparent at the time of surgery (primary reason for adjuvant therapy)
- Primary therapy of metastatic colon and rectal cancers
9
Q
Fluorouracil for colorectal cancer
A
- Most extensively studied and used agent in colorectal cancer
- Used in both adjuvant and metastatic setting
- Pattern of toxicity differs between bolus administration and continuous infusion
- Grade 3 & 4 hematological toxicity is more common w/ the bolus regimens, whereas the infusion regimens are more likely to show “hand-foot” syndrome (palmar-plantar erythrodysethesia)
- Essential component of selected irinotecan or oxaliplatin regimens
10
Q
Hand-foot syndrome
A
- Painful reddening of the skin that can proceed to desquamation
- Px should be counselled to report any changes to palms and soles ASAP
- Prevention measures include moisturizing liberally and avoiding sources of heat and friction
- Tx measures can include topical anesthetics, application of cold, oral analgesics
11
Q
Irinotecan for colorectal cancer tx
A
- Topoisomerase 1 inhibitor
- Used in metastatic setting
- Has activity as a single agent in px w/ fluorouracil-resistant disease
- Currently first line agent for tx of metastatic colorectal cancer in combo w/ fluorouracil and leucovorin
- Real problem w/ diarrhea (early onset, < 24 h, & late onset, 3-5 days after tx)
- Give a dose of atropine just before starting irinotecan to prevent early onset diarrhea (early onset is muscarinic in nature, late onset isn’t)
- Can use loperamide for late onset
12
Q
Describe the dosing for loperamide for irinotecan-induced diarrhea
A
- Take 4 mg at first onset of water stools, then 2-4 mg every 2 h until 12 h w/ no bowel movement, up to 32 mg/day
- Most px don’t reach max daily dose but it is safe from them to take max daily dose for 2-3 days, then they should contact their oncologist
13
Q
Oxaliplatin for colorectal cancer tx
A
- Currently approved in both adjuvant and metastatic setting
- Better response rates when combined w/ fluorouracil and leucovorin; most regimens have fluorouracil delivered as a continuous IV infusion
- Major AE = peripheral neuropathy, laryngeal spasm, and cold intolerance
14
Q
Raltitrexed for colorectal cancer tx
A
- Thymidilate synthetase inhibitor
- Currently approved in metastatic setting
- Deaths in Europe secondary to lack of dose reductions in px w/ renal dysfunction (so hardly used now)
15
Q
Capecitabine for colorectal cancer tx
A
- First oral fluoropyrimidine that allows therapy to be delivered at home similar to IV fluorouracil
- Metabolized to fluorouracil (greater metabolism in cancer cells than normal cells)
- Used in both adjuvant and metastatic setting
- Designed to take BID for 2 weeks w/ 1-week break (cycle = 3 weeks)
- If pt doesn’t take a break, can get serious diarrhea and hand-foot syndrome
