___________________________________________________________________________ Colorectal Cancer
Physical Examination With increasingly widespread and effective screening, colorectal cancer is frequently detected at an earlier, asymptomatic phase. Physical examination findings early in the disease course can be normal or nonspecific (e.g., fatigue, weight loss) [114; 187]. With more advanced colon cancer, common clinical presentations include iron-deficiency anemia, rectal bleeding, abdominal pain and tenderness, change in bowel habits, intestinal obstruction or perforation, hepatomegaly, and ascites. Right-sided lesions are more likely to bleed and cause diarrhea, while left-sided tumors are usually detected later and may present as bowel obstruction [114; 187]. In addition to these signs and symptoms in colon cancer, physical examination of patients with rectal cancer may reveal a palpable mass and bright red blood in the rectum. Adenopathy, hepatomegaly, or pulmonary signs may be present with metastatic rectal cancer. Proctosigmoidoscopy and digital rectal examination should be performed to determine tumor distance from the anal verge, mobility, and position relative to the sphincter complex. Signs and Symptoms Healthcare professionals should be attentive to both common and uncommon signs and symptoms during the history and physical exam that suggest colorectal cancer. More common diagnostic factors include increasing age, rectal bleeding, rectal mass, change in bowel habits, family history, abdominal mass or distension, and anemia [171; 189; 190; 191]. Rectal Bleeding Although patients presenting with rectal bleeding may have a benign condition, this is a common symptom in patients with colon and rectal cancer. A primary care study found a positive correlation between each new episode of rectal bleeding in patients older than 45 years of age and colorectal cancer [191]. Change in Bowel Habit Especially with rectal bleeding present, an increased frequency or looser stools is common in left-sided colorectal cancer. Bowel habit changes with reduced frequency and hard stools have low predictive value for colorectal cancer. Rectal Mass Palpable rectal mass is present in 40% to 80% of patients with rectal cancer [192]. Assessment using digital rectal examination is useful to estimate tumor proximity to the sphincter but unreliable to determine tumor involvement of the pelvic wall and suitability for surgery. These latter investigations are more accurately assessed by magnetic resonance imaging (MRI) and transrectal endoscopic ultrasound. Positive Family History Although only 10% to 20% of patients with colorectal cancer have a positive family history of colorectal cancer, persons with one affected first-degree relative are more than twice as likely
• MSI: Present in 15% of colorectal cancers, moderate evidence suggests this mutation may predict response to 5-FU and irinotecan. • 18qLOH/ SMAD4 loss: Present in 50% of colorectal cancers, moderate evidence suggests this mutation may predict resistance to 5-FU. • COX-2 overexpression: Emerging data show that colorectal cancer tumors with COX-2 overexpression are significantly associated with worse outcomes. This is consistent with the body of research associating long-term COX-2 inhibitor use with decreased rates of adenoma and colorectal cancer development and/or recurrence.
DIAGNOSIS AND STAGING OF COLON AND RECTAL CANCER
DIAGNOSTIC WORKUP Patients with colorectal cancer typically present in one of three ways: • Outpatients with suspicious symptoms and signs • Asymptomatic persons discovered by routine screening • Emergency admission with intestinal obstruction, peritonitis, or bleeding A diagnosis of colorectal cancer is confirmed and other conditions ruled out by conducting a thorough patient history and physical examination and using appropriate testing. During the workup, the clinician should be mindful that, unless otherwise indicated, surgical resection is the first-line treatment for localized malignancy and is the only curative option for colorectal cancer. Thus, the diagnostic workup involves characterization of the malignancy and preoperative assessment. History Patient history and physical examination are the foundations of assessment. A thorough disease history should be obtained by eliciting disease-specific symptoms, associated symptoms, and family history. A cancer-specific history helps direct the exploration of associated pathology or metastatic disease and any further workup. When possible, all patients should undergo a full colonic evaluation with histologic assessment of the colorectal lesion before treatment. Patients should also be assessed for their fitness to undergo surgery, including assessment of cardiac risk, and preoperative radiologic staging should be routinely performed [187; 188]. The incidence of colorectal cancer increases with age. Patients younger than 44 years of age account for fewer than 5% of cases, and the mean age at diagnosis is 71 years. Men and women older than 50 years of age have similar rates of colorectal cancer. However, the colorectal cancer prevalence in men increases in tandem with age beyond 50 years [97].
69
MDFL2626
Powered by FlippingBook