Incidence of colorectal cancer is different in every country. Australia, New Zealand, Europe, and North America are estimated to have the highest incidence rates, whereas Africa and South Central Asia have the lowest incidence rate.[1,6] The differences is due to the differences in dietary habits and environmental exposure. However, studies on major risk factors for colorectal cancer and global distribution in children are limited. In Korea, colorectal cancer is the third most common cancer in adults, but 5-year prevalence in patients aged ≤20 years is about 12 per 100,000 (2012 statistics). Furthermore, rectal cancer only occurs in patients aged above 15 years and the rate of colon cancer increases with age. Incidence rate of colorectal cancer in US pediatric population was about 1.3 per one million. In Japan, out of 700 pediatric malignant solid tumors annually, 1 to 3 were estimated to be colon carcinomas. In adults, despite the high incidence rate, mortality of colorectal cancer is low because of early detection and management. Therefore, early detection of colorectal cancer in young patients by extensive evaluation will contribute to more reported cases and will affect its incidence rate.
Symptoms of colorectal cancer in pediatric patients are not different from those seen in adults. Clinical manifestations differ depending on the tumor location; therefore, nonspecific gastrointestinal symptoms can be seen before the disease reaches an advanced stage.[10,11] Underlying diseases and familial history of cancer could be vital information in suspecting colorectal cancer in adults. De novo carcinoma in a normal colon changes to malignancy faster than in a colon with chronic bowel diseases; therefore, fewer patients in the pediatric population have underlying diseases at first diagnosis, when compared with the adult population. In cases, chronic abdominal pain, hematochezia, or melena, persistent iron deficiency, and anemia can be related to colorectal cancer. Typical symptoms of colorectal cancer include vomiting, severe abdominal pain, and bloody stools; however, in children, the symptoms might be restricted to only altered bowel habits. Location of cancer can be a major factor in manifestation of specific symptoms. Similar to the first case presented, a right-sided cancer can manifest as mass, anemia, diarrhea, or intussusception. Left-sided cancer can cause bleeding, obstruction, or altered bowel habits, but similar to the second case, initial symptoms could be only a change in bowel habits with abdominal pain and diarrhea. Environmental factors can contribute to different prevalence in different age groups, but a major reason for the difference in the detection rate is the colorectal cancer screening system that has can potentially diagnose asymptomatic patients with colorectal cancers.
Unlike in adults, familial cancer history is not strongly associated with colorectal cancer in children. However, if patients who have familial cancer history have chronic symptoms, further imaging tests such as abdominal CT or endoscopy should be considered. Tumor makers can also be used to suspect the presence of colorectal cancer. Many serum markers are associated with colorectal cancer, especially CEA. However, serum markers, including CEA, have a low diagnostic ability when compared with radiologic examination due to low sensitivity (only 46%) and a possibility of false-positives, including in other benign tumors. However, CEA levels of over 5 ng/mL predict a worse prognosis than lower levels.
As mentioned above, any symptoms indicative of colorectal cancer can be an indication for further imaging tests. Once colorectal cancer is suspected, barium enema, ultrasound abdominal examination, colonoscopy, abdominal CT, and therapeutic surgical resection can be performed. Barium enema is widely available and can be used in patients with symptoms of colorectal cancer. However, barium enema takes more time than abdominal CT and it is difficult to detect early states of cancer, which result in a low specificity. Colonoscopy is more useful because right ascending colon and transverse colon carcinomas are more common in pediatric patients. In Korea, pediatric endoscopic procedures can be commonly performed without general anesthesia at an endoscopy unit. In a comparative study in which 2527 patients were assigned to receive double contrast barium enema, the detection rate for colorectal cancer was significantly lower than that for CT or colonoscopy.
The Tumor Node Metastases staging system of the American Joint Committee on Cancer for International Cancer Control is the staging system of choice for colorectal cancer. To predict the prognosis, Duke and MAC staging systems are used together. In both these staging systems, stages A and B are curable. However, as in the second case presented, most pediatric patients are diagnosed with advanced-stage carcinoma with poor prognosis. Another reason for poor prognosis in pediatric patients is histological grading. In adults, mucinous adenocarcinoma accounts for less than 5% of cases. However, in children, more than 50% of patients are diagnosed with mucinous adenocarcinoma, which carries a poor prognosis. If a patient is diagnosed with colorectal cancer that is curable, complete resection is the ideal management. Left-sided tumors require subtotal colectomy, and right-sided tumors require extended hemicolectomy. According to TNM staging, adjuvant chemotherapy and radiotherapy are required, but these treatment regimens are controversial.
Mucinous adenocarcinoma, which has worse prognosis, accounts for higher incidence in young patients. Therefore, early detection can increase the possibility of curing cancer as described in the first case. In the second case, she showed the symptom of weight loss and anemia over 6 months. We believe that if earlier evaluation was performed, the patient might have lived. Since routine diagnostic colonoscopy in Korea is recommended for people aged >40 years, colorectal cancer in pediatric patients is detected late and in advanced stages. In Korea, pediatric endoscopy can be performed easily using deep sedation without general anesthesia at an endoscopic unit. In summary, if children present with persistent weight loss, bloody stools, or anemia, they need to undergo further imaging investigations or endoscopy.
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Keywords:Copyright © 2017 The Authors. Published by Wolters Kluwer Health, Inc. All rights reserved.
adenocarcinoma; children; colon cancer