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Colorectal cancer: Difference between revisions
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<section begin="clinical biochemistry" />'''Colorectal carcinoma''' (<abbr>CRC</abbr>) refers to all cancers that can affect the colon and rectum. Carcinomas in the colon are the most common malignancy in the <abbr>GI</abbr>-tract, accounting for 95% of all GI cancers. | <section begin="oncology" /><section begin="clinical biochemistry" />'''Colorectal carcinoma''' (<abbr>CRC</abbr>) refers to all cancers that can affect the colon and rectum. Carcinomas in the colon are the most common malignancy in the <abbr>GI</abbr>-tract, accounting for 95% of all GI cancers. <section end="clinical biochemistry" /> | ||
<section end="clinical biochemistry" /> | |||
CRC is the third most common type of cancer, but it’s the second most common cause of cancer-related death. It accounts for 10% of the world’s cancers. It’s mostly a disease of elderly, affecting those in their 60s and 70s. >90% of colorectal cancers develop from [[Colonic polyps|adenomatous polyps]] of the colon. | CRC is the third most common type of cancer, but it’s the second most common cause of cancer-related death. It accounts for 10% of the world’s cancers. It’s mostly a disease of elderly, affecting those in their 60s and 70s. >90% of colorectal cancers develop from [[Colonic polyps|adenomatous polyps]] of the colon. | ||
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== Pathology == | == Pathology == | ||
Adenocarcinoma is the most common type, accounting for 95% of cases. Other histological types include adenosquamous carcinoma, and spindle cell carcinoma. | Adenocarcinoma is the most common type, accounting for 95% of cases. Other histological types include adenosquamous carcinoma, and spindle cell carcinoma.<section end="oncology" /> | ||
Adenocarcinomas are usually solitary masses, either polypoid or ulcerated. These cancers are synchronous in a few percent of cases, meaning that more than one primary tumour is present at the same time. | Adenocarcinomas are usually solitary masses, either polypoid or ulcerated. These cancers are synchronous in a few percent of cases, meaning that more than one primary tumour is present at the same time. | ||
Like all cancers they are graded based on their differentiation. Well differentiated tumors are low grade and form well-formed glands or tubules that somewhat resembles adenomatous epithelium. Moderately differentiated tumors are the most frequent type, where glands and tubules are irregular and abnormal. Poorly differentiates tumors produce few glands, and the majority of the tumor consists of sheets of cells without glands. | Like all cancers they are graded based on their differentiation. Well differentiated tumors are low grade and form well-formed glands or tubules that somewhat resembles adenomatous epithelium. Moderately differentiated tumors are the most frequent type, where glands and tubules are irregular and abnormal. Poorly differentiates tumors produce few glands, and the majority of the tumor consists of sheets of cells without glands. | ||
=== Pathogenesis === | === Pathogenesis === | ||
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These molecular changes are clinically important because we nowadays have drugs which may target the specific mutations, if present in that specific patient. | These molecular changes are clinically important because we nowadays have drugs which may target the specific mutations, if present in that specific patient. | ||
<section begin="oncology" /> | |||
=== Metastasis === | |||
This type of cancer can metastasize by the lymphogenic way to regional lymph nodes. It can also spread by the portal circulation to the liver, or by the caval circulation to the lung if the tumor originated in the lower third of the rectum. Peritoneal seeding is uncommon. Other common sites of metastasis are bone and ovary. | |||
== Clinical features == | == Clinical features == | ||
The most important symptoms are those of lower [[Gastrointestinal bleeding|GI bleeding]] (haematochezia, melena, [[Iron deficiency anaemia|iron-deficiency anaemia]]) or altered bowel habits. Altered bowel habits is more common for left-sided cancers compared to right-sided, due to the smaller lumen of the left-sided colon. Alternating diarrhoea and constipation is a | The most important symptoms are those of lower [[Gastrointestinal bleeding|GI bleeding]] (haematochezia, melena, or occult bleading leading to [[Iron deficiency anaemia|iron-deficiency anaemia]]) or altered bowel habits. Altered bowel habits is more common for left-sided cancers compared to right-sided, due to the smaller lumen of the left-sided colon. Alternating diarrhoea and constipation is a typical sign. Abdominal pain is a less frequent symptom. Rectal cancers cause tenesmus and incomplete defecation. | ||
Metastases are present at presentation in 20% of cases. Distal rectal cancers may be palpated on DRE. | Metastases are present at presentation in 20% of cases. Distal rectal cancers may be palpated on DRE. | ||
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[[CT]] colonography (virtual colonoscopy) is an alternative to colonoscopy, but it does not allow for biopsy or removal. | [[CT]] colonography (virtual colonoscopy) is an alternative to colonoscopy, but it does not allow for biopsy or removal. | ||
Once the diagnosis of colon cancer has been made, a CT of the chest, abdomen, and pelvis is required for staging. For rectal cancers, MRI is used. | Once the diagnosis of colon cancer has been made, a CT of the chest, abdomen, and pelvis is required for staging. For rectal cancers, MRI is used, and a transrectal ultrasound may be necessary to determine the T and N stage.<section begin="clinical biochemistry" />[[CEA]] is the tumour marker most specific for CRC and should be measured upon diagnosis. Elevated CEA is associated with a worse prognosis, and CEA which doesn’t normalise postoperatively is indicative of persistent disease. Microcytic or normocytic anaemia (due to chronic GI blood loss) or faecal occult blood are typical findings in CRC.<section end="clinical biochemistry" /> | ||
<section begin="clinical biochemistry" /> | === Staging === | ||
[[CEA]] is the tumour marker most specific for CRC and should be measured upon diagnosis. Elevated CEA is associated with a worse prognosis, and CEA which doesn’t normalise postoperatively is indicative of persistent disease. Microcytic or normocytic anaemia (due to chronic GI blood loss) | CRC is staged like this: | ||
<section end="clinical biochemistry" /> | |||
* Stage 0 – carcinoma in situ (cancer is in the mucosa) | |||
* Stage I – cancer invades the muscularis mucosa | |||
* Stage II – cancer invades beyond the muscularis mucosa | |||
* Stage III – cancer has spread to regional lymph nodes | |||
* Stage IV – cancer has spread distally (distant metastasis) | |||
== Treatment == | == Treatment == | ||
The gold standard treatment for <abbr>CRC</abbr> is radical surgery. | The gold standard treatment for <abbr>CRC</abbr> is radical surgery. CRC is one of the few cancers in which M1 cancers can be cured, as surgical resection of liver and/or lung metastases (metastasectomy) may allow for cure. | ||
Stages I-III can usually be attempted cured, with surgical resection with or without chemotherapy. Some stage IV CRCs may be cured, if there are only a few metasases in the liver or lung which can be removed surgically, although complete cure is rare. In most cases of stage IV disease, treatment is only palliative. | |||
=== Surgical treatment === | |||
Options include left or right hemicolectomy, sigmoid colectomy, or total or subtotal colectomy. This may be performed [[Laparotomy|open]], [[Laparoscopic surgery|laparoscopically]], robot-assisted, etc. At least 12 regional lymph nodes must be removed for proper surgical staging. Rectal cancer is treated with ''total mesorectal excision'' (TME) in most cases, or more modern techniques like ''transanal endoscopic microsurgery'' (TEM). | |||
Surgery may also be used [[Palliative surgery|palliatively]], either by resection, bypass operation, stoma formation, or by stenting. | Surgery may also be used [[Palliative surgery|palliatively]], either by resection, bypass operation, stoma formation, or by stenting. | ||
=== Systemic treatment === | |||
Chemotherapy (usually [[FOLFOX]] or [[FOLFIRI]]) may be used neoadjuvant or adjuvant in stages II-IV. Biological therapy may be used palliatively and include anti-VEGF and anti-EGFR antibodies. Targeted therapy, with multi-tyrosine kinase inhibitors like regorafenib, may also be used palliatively. | |||
=== Radiotherapy === | |||
Radiation is not used for colon cancer (or any intraabdominal cancer) because the small bowel is very sensitive to radiation. Radiotherapy may be used for rectal cancer, as it lies in the pelvic region. | |||
== Screening == | == Screening == | ||
Screening is important to reduce the incidence of CRC, as most CRCs develop from adenomatous polyps which take years to develop into cancer. In Europe, screening programs for CRC are in development or recently launched. Generally, people above 50/55 should be screened with [[colonoscopy]], or alternatively, with a [[faecal occult blood test]]. | Screening is important to reduce the incidence of CRC, as most CRCs develop from adenomatous polyps which take years to develop into cancer. In Europe, screening programs for CRC are in development or recently launched. Generally, people above 50/55 should be screened with [[colonoscopy]], or alternatively, with a [[faecal occult blood test]].<section end="oncology" /> | ||
<noinclude>[[Category:Gastroenterology]] | <noinclude>[[Category:Gastroenterology]] | ||
[[Category:Gastrointestinal surgery]]</noinclude> | [[Category:Gastrointestinal surgery]] | ||
</noinclude> | |||