Colorectal cancer: Clinical sciences

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Introduction0:00–0:33

Colorectal cancer most commonly refers to adenocarcinoma, and it’s usually located in the colon, but it can be found in the rectum as well.
The presentation of colorectal cancer is not always clear, so early detection depends on screening. Staging is based on the TNM classification, meaning that tumor size, lymph node invasion, and the presence of metastasis are taken into account when making a treatment plan.
When assessing a patient with signs and symptoms suggestive of colorectal cancer, you should first perform an ABCDE assessment to determine if your patient is stable or unstable.

Unstable patient0:33–1:03

If the patient is unstable, start acute management and stabilize the airway, breathing, and circulation. Next, obtain IV access and initiate IV fluids for resuscitation.
Finally, be sure to monitor their vital signs, including pulse oximetry, blood pressure, and heart rate.Once these important steps are done, you should determine what caused their instability.

Obstruction & perforation1:03–2:27

Tumors located on the descending colon are generally infiltrating masses, meaning they tend to be ring-shaped and involve the whole circumference of the colonic wall.
This causes luminal narrowing, referred to as napkin-ring constriction, or apple core lesions because of their appearance on imaging.
What's important is that these lesions can lead to an obstruction, which can result in bowel necrosis and perforation. These patients typically have a history of abdominal pain, nausea, and vomiting; and will also have changes in bowel habits, as well as small caliber or narrow stools described as pencil-thin.
On a physical exam, you might find abdominal distention, and signs of peritonitis like rebound pain and guarding. Finally, labs might show leukocytosis.
Based on these findings, you should suspect obstruction or perforation caused by the tumor. Okay, now that we have a diagnosis in mind let’s talk about confirming your suspicion.
Your next step is to order an upright abdominal x-ray. You might see large bowel dilatation, which indicates obstruction; and pneumoperitoneum, which means that perforation has occurred.
If this is the case, call the surgical team for an emergent laparotomy with resection and send it to pathology, which will provide the final diagnosis.Okay, before discussing pathology results, let’s go back to H&P to talk about another way colorectal cancer might cause instability.

Acute GI bleed2:27–3:58

As they grow, some tumors become ulcerated and have fragile blood vessels. If these vessels burst, they may cause acute bleeding.
These patients typically present with rectal bleeding and abdominal pain, and may have a history of changes in bowel habits.
Additionally, on digital rectal exam, you might see gross blood, and low rectal masses can sometimes be palpated. Finally, labs might show anemia.
Based on these findings you should suspect acute GI bleed caused by a colorectal tumor. At this point, you should immediately address the acute bleed and stabilize the patient.The next logical step is to confirm your diagnosis.
To do this, order a colonoscopy with a biopsy. Colonoscopy might reveal overlaying erosion or ulceration, friable mass, synchronous lesions, and active bleeding.
If you see these signs, that would mean that the patient has a tumor that caused bleeding. The next step is to get a biopsy to assess the pathology results and determine if the mass is malignant or benign.Okay, let’s take a look at the pathology results for both patients with perforation, and those with active bleeding.
Biopsy showing malignancy leads to a diagnosis of colorectal cancer. However, if there’s no malignancy, consider an alternative diagnosis.Alright, now that unstable patients are diagnosed, let’s talk about stable patients.

Stable patient3:58–5:28

The first step here is to obtain a focused history and physical, as well as labs like CBC. Now, patients might present with or without obvious symptoms of colon cancer.First up, symptomatic patients typically report changes in bowel habits, rectal bleeding, and weight loss.
On a physical exam, you might find a palpable abdominal mass, abdominal distention, or tenderness. On a digital rectal exam, you might see gross blood or palpate low rectal masses.
Finally, labs might show signs of anemia.On the other hand, asymptomatic patients might come for several reasons. First, they might have a positive screening fecal occult blood test or fecal immunochemical test.
Then, they might come in because of a positive screening colonoscopy. Finally, they might have iron deficiency anemia requiring further workup.
In any case, a physical exam is typically unremarkable, while labs might also show signs of anemia.Here’s a high-yield fact!
Some colorectal cancers arise from genetic mutations that can be associated with cancer syndromes. Therefore, be sure to assess for a family history of syndromes like familial adenomatous polyposis, Peutz-Jeghers syndrome, Juvenile polyposis syndrome, Gardner syndrome, Turcot syndrome, and Lynch syndrome.
Okay, with both symptomatic and asymptomatic patients, you should get a colonoscopy with biopsy to find the cause of their symptoms or positive screening tests.

Colonoscopy + biopsy5:28–6:32

Colonoscopy is the most accurate diagnostic test, since it allows to localize and biopsy lesions throughout the large bowel, detect synchronous neoplasms, and remove polyps.
If a full colonoscopy can’t be performed because of obstruction, they may need surgical intervention to resect the obstructing mass, and the surgeon can do a colonoscopy in the operating room if needed.Logically, if there are no masses or signs of colorectal cancer on colonoscopy, or if biopsy results are negative, consider an alternative diagnosis.
Now, the vast majority of colorectal cancers are endoluminal masses that arise from the mucosa and protrude into the lumen.
They may be exophytic or polypoid in nature, and may be friable, necrotic, or ulcerated with associated bleeding. Additionally, the biopsy is positive for malignancy.

Colon cancer6:32–9:46

Once the diagnosis of colon cancer is made, you can move on to TNM staging with a CT of the chest, abdomen, and pelvis. Cancer staging is based on the TNM system, which stands for Tumor size and extent, spread to Lymph Nodes, and Metastasis or spread to distant parts of the body.
The treatment depends on the TNM stage. In general, early-stage cancers can be resected with surgery, while advanced-stage cancers may require different combinations of chemotherapy, radiation, and surgery when possible.
Next to TNM staging, you should obtain carcinoembryonic antigen, or CEA, to get a baseline, which will help you follow if the treatment is working or not down the line, as well as if there’s a recurrence.Okay, let’s see how staging influences the treatment.
The main thing to determine is whether or not there are distant metastases. If there are no distant metastases, surgical resection is the treatment of choice.Before getting the surgery, check if the tumor is small and localized, meaning it’s limited to the inner surface of the bowel, only involving mucosa and submucosa layers; or locally advanced, meaning the tumor is spreading to nearby organs or lymph nodes.
Small, localized tumors can go straight to surgical resection. In addition to surgery, it is important to send the resected mass for pathologic confirmation of clear margins and evaluation of the surrounding lymph nodes.
If the margins are not clear, or there are cancer cells in the lymph nodes, the patient should be started on adjuvant chemotherapy after resection to take care of any remaining cancer cells.
On the other hand, locally advanced tumors first require neoadjuvant therapy. This means that they will be treated with chemotherapy or chemoradiation to try and shrink the tumor and destroy any cancer cells in lymph nodes.
After neoadjuvant therapy, they can get surgical resection, and if needed after that, adjuvant chemotherapy. Okay, let’s go back to staging and talk about patients with distant metastases.
If there are distant metastases, some cases might still be consid ered resectable. This includes patients with limited metastases to the liver or lungs.
In this case, the patient can go directly to surgical resection of the primary tumor and metastases. Unfortunately, most cases are considered unresectable, so they should be started on chemotherapy.
Once the full course of chemotherapy is complete, you can obtain a repeat CT or MRI to assess if the tumor responded to it.
This is termed “restaging.” If the areas of metastases shrunk enough that they would have been considered resectable originally, and the patient is a surgical candidate from a performance status standpoint, the next step is surgical resection of the tumor and any metastatic disease.
However, if they don’t respond to treatment, you can switch to second line chemotherapy regimens or immunotherapy; in addition, start supportive care and consider palliative care for the patient.
Here is a clinical pearl! Even if there’s unresectable metastatic disease, if the patient is at high risk for obstruction or bleeding, palliative surgery can be considered, even prior to chemotherapy.
Now, let’s go back to the colonoscopy. If the tumor is found in the rectum, you can confirm the diagnosis of rectal cancer.

Rectal cancer9:46–12:16

On colonoscopy, the mass looks the same as colon cancer. So it’s endoluminal, exophytic, and polypoid, with possible bleeding and necrosis, as well as positive biopsy for malignancy.
As before, the next step involves TNM staging with CT of the chest, abdomen, and pelvis. Additionally, an MRI of the pelvis should be obtained for rectal cancer in order to locally stage the depth of transmural invasion, assess the presence or absence of invasion into adjacent structures, and note the presence of any perirectal nodal involvement.
In patients that can't have an MRI, such as those with a pacemaker, transrectal ultrasound can be used for staging depth of invasion and nodes.
Finally, order CEA to get a baseline value.Let’s first go over treatment for patients with no distant metastases. Rectal tumors that are small and localized can be resected through endoscopic transanal excision, local excision, or surgical resection.
On the other hand, locally advanced tumors require neoadjuvant therapy before anything else. Once the course of treatment is complete, you should assess its effect with proctoscopy and possibly another MRI to restage the tumor.
Now, if there's a positive response, the tumor does not significantly increase in size and there is no evidence of new metastatic disease, call the surgical team for possible resection.
After surgery, if margins are not clear, or there are cancer cells in the lymph nodes, the patient should be started on adjuvant chemotherapy.Lastly, let’s go over patients with distant metastases.
Again, some cases might still be considered resectable, including patients with limited metastases to the liver or lungs, so they can get surgical resection of the primary tumor and metastases.
On the other hand, unresectable cases should be started on chemotherapy.Once the full course of chemotherapy is complete, you can assess the response by restaging the tumor.
If there’s a positive response, meaning the areas of metastases shrunk enough, the next step is surgical resection. However, if there’s minimal or no response to treatment, consider switching to second line chemotherapy regimens or immunotherapy, as well as supportive and palliative care.

Review12:16–13:35

Alright, as a quick recap… Colorectal cancer most commonly refers to adenocarcinoma. The presentation of colorectal cancer is not always clear, so early detection depends on screening.
Unstable cases may occur due to obstruction or perforation, which should be assessed with an abdominal x-ray followed by emergent laparotomy and resection for excisional biopsy; or due to acute GI bleed, which should be addressed and then evaluated with colonoscopy and biopsy.
Once the complication of colorectal cancer is managed, biopsy results should be assessed to confirm the diagnosis. When it comes to stable patients, they can go straight to colonoscopy and biopsy to make a diagnosis.
Colorectal cancer should be staged with CT of the chest, abdomen, and pelvis, and treated according to the TNM stage. In general, small, localized tumors can be resected with surgery, while locally advanced tumors typically need neoadjuvant therapy before surgical resection.
After surgery, if margins are not clear, or there are cancer cells in the lymph nodes, start adjuvant chemotherapy. Lastly, patients with distant metastasis may require different combinations of chemotherapy, radiation, and surgery when possible, as well as supportive and palliative care.
Colorectal cancer: Clinical Sciences: Video | Osmosis