Rectal Cancer

Dr. Suvansh Raj NirulaMBBS

February 25, 2021

February 25, 2021

Rectal Cancer
Rectal Cancer

Cancer that starts in the rectum or the final portion of the large intestine is called rectal cancer. It is part of a larger group of cancers called colorectal cancer, which involves the colon and the rectum. The gut, or the digestive tract, begins at the mouth, through which food is passed into the esophagus. Through the esophagus, the food enters the stomach, where some of it is digested. The contents of the partially digested food are then passed into the small intestine for further digestion. After all the food is digested, it is passed to the large intestine or the colon. Here, water and other substances are absorbed and the final waste product is removed from the bowel through the rectum and out of the body from the anus.

Signs and symptoms of rectal cancer

Rectal cancer can present with some of the following clinical signs and symptoms in the early stages of disease. The presence of any of these clinical features warrants a consultation with a doctor to rule out the possibility of a serious condition like rectal cancer.

Some other non-specific signs and symptoms can appear with rectal cancer. However, as these are not exclusive to rectal cancer, they are not definitive diagnostic features. Some such symptoms include:

When rectal cancer has spread to distant parts of the body, some more clinical features specific to the new metastatic deposits can arise:

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Causes of rectal cancer

While the cause of colorectal cancers is still not known, evidence suggests that underlying genetic anomalies could play a role. Some such anomalies are:

  • Inherited genetic mutations: For example, familial adenomatous polyposis (FAP) due to an inherited adenomatous polyposis coli (APC) gene, Lynch syndrome (also called hereditary non-polyposis colon cancer) and Peutz-Jeghers syndrome, caused by inherited changes in the STK11 (LKB1) gene.
  • Acquired genetic mutations: Various defects and changes to an individual’s DNA can be acquired in a lifetime due to habits such as smoking. Some such mutations can lead to rectal cancer.

(Read more: How to quit smoking)

Risk factors of rectal cancer

Besides inherited and acquired genetic mutations, other risk factors can play a role in the development of rectal cancer:

  • Advancing age, especially after 50 years of age
  • Make sex, as rectal cancer is more common in them
  • Ethnicity, as people of African descent are at a higher risk
  • Family history of colorectal cancer
  • Previous cancer radiation therapy
  • Ovarian cancer
  • Other pre-existing conditions of the bowel including
  • Inflammatory bowel disease (IBD)
  • Colorectal polyps
  • Smoking
  • Heavy alcohol consumption
  • Obesity
  • Type 2 diabetes mellitus
  • Inactive sedentary lifestyle
  • An unhealthy diet that consists of processed food and red meat

(Read more: Healthy Foods)

Stages of rectal cancer

Following are the five stages of rectal cancer:

  • Stage 0 or carcinoma in situ: Where only the innermost layer of the rectal wall contains abnormal cells. Carcinoma in situ means that the cancer is restrained to the one site where it began.
  • Stage 1: Where the cancer cells have spread past the innermost layer of the rectum wall but have not infiltrated into any lymph nodes.
  • Stage 2: In stage 2A, cancer cells have spread into or through the outer muscle layer of the rectum wall, but not to any lymph nodes. In stage 2B, the cancer has spread into the abdominal lining.
  • Stage 3: In this stage, the cancer cells have spread through the outermost muscle layer of the rectum and to one or more lymph nodes. Based on the number and site of lymph nodes invaded, stage 3 is divided into substages 3A, 3B and 3C.
  • Stage 4: Metastasis has occurred in this stage. This means that cancer cells have spread to distant sites, like the liver or lungs. This holds a poor prognosis.
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Diagnosis of rectal cancer

The doctor begins by taking a thorough medical history of the patient. Details about the appearance as well as the sequence of symptoms will be noted. Attention will be paid to any predisposing risk factors, lifestyle diseases, pre-existing rectal or colon polyps and a family history of colorectal cancer. Following this, the patient will be subjected to a clinical physical examination.

A general medical examination is conducted, in which many signs of an underlying disease like jaundice, anemia and fingernail clubbing can be noted. A systemic exam is conducted afterwards. Abdominal examination is of utmost importance to rule out any other underlying conditions. Other systems are also examined to find signs of possible underlying metastasis if any. Following a systemic examination, a digital rectal examination may be done. The doctor will apply a lubricant jelly and then examine the anal opening and rectum with their gloved fingers. A proctoscope may be introduced into the rectum to view the lumen better. However, to visualise the colon further, special tools may be used.

Tests for rectal cancer

Investigations required for an accurate diagnosis of rectal cancer are:

  • Stool tests: Fecal occult blood test (FOBT) are done in order to detect blood in stool that may not be visible to the naked eye. Two types of tests are commonly used for this; a sample of stool is required for both.
    • Guaiac based fecal occult blood test (gFOBT): Where the stool sample is applied on a card containing guaiac. The colour of the card changes if occult blood is present in the stool. Red meat and NSAIDs should be avoided before this test to avoid interference.
    • Fecal immunochemical testing (FIT): This test detects hemoglobin, the main protein of blood, in stool and the test results are not affected by food or drugs. It is considered to be a more accurate test.
  • Blood tests:
    • Complete blood count: Hemoglobin levels can be low due to anemia, caused by bleeding from the rectum.
    • Blood glucose levels: Can detect diabetes mellitus.
    • Liver function test: Liver enzyme derangements and jaundice may be caused by metastasis.
    • ESR and CRP: These markers of inflammation can suggest inflammatory bowel disease (IBD).
    • Blood levels of (Carcinogenic Embryonic Antigen) CEA: A tumour marker that can be elevated in rectal cancer.
  • Visualisation investigations: The entire colon is visualised to detect any other tumours growing in the remaining length of the large intestine.
    • Sigmoidoscopy: A flexible tube is inserted through the rectum and into the sigmoid colon (the last portion of the large intestine before the rectum begins). It can help visualise any growths or polyps better.
    • Colonoscopy: The patient prepares a day in advance by taking prescribed purgative medications that evacuate the bowels for better visualisation. A tube is inserted through the rectum, after application of lubricant and local anaesthetic, it helps visualisation the entire length of the colon. A biopsy, or the taking of tissue samples from suspicious growths can also be done. These tissue samples are investigated microscopically for cancer cells.
  • Radiological imaging investigations:
    • X-ray with barium enema: A contrast dye is infused through the rectum and X-rays are taken. This helps visualise any abnormal growths.
    • CT scans: They help visualise the anatomy of the rectum and colon with more precision.
    • Chest X-ray: Liver metastasis may appear on film.
    • For people with an average risk for rectal cancer, regular screening is advised with stool and visual examination (like colonoscopy) after the age of 45. For people with added risk factors, more frequent screening with more specific tests should be started before the age of 45.

Treatment of rectal cancer

Treatment of rectal cancer depends on the stage of cancer when it is first diagnosed. The treating doctor will decide the most appropriate treatment factoring in the size of the tumour, extent of spread, the patient’s age and general health status. It can involve a mix of surgical resection (colorectal cancer surgery), chemotherapy, radiation therapy and immunotherapy. Following are some rough guidelines, based on the stage of rectal cancer:

  • Stage 0 (carcinoma in situ) rectal cancer:
    • Removal of suspicious tissue during colonoscopy
    • Resection of the suspicious area by operating surgically, with or without removal of the surrounding tissue margin.
  • Stage 1 rectal cancer: A combination of local excision or resection surgically, followed by chemotherapy and/or radiation therapy is most often the therapy of choice.
  • Stage 2 and stage 3 rectal cancer: More extensive surgical removal is needed most of the time. A wider margin is also excised. Adjuvant chemotherapy and/or radiation therapy are used to improve the clinical outcome by significantly reducing chances of recurrence.
  • Stage 4 rectal cancer with metastasis: 
    • Extensive surgery is required, often in more than one part of the body to address the primary cancer tumour and the secondary cancer metastasis deposits. 
    • Specialised surgical techniques like cryotherapy can be tried as well.
    • Adjuvant therapy with chemotherapy drugs and/or radiation therapy in combination help kill cancer cells more effectively and reduce the chances of recurrence.
    • Radio frequency ablation is a technique that utilises high energy radiation to kill cancer cells in tumours in a targeted fashion.
    • Immunotherapy with targeted monoclonal antibodies or angiogenesis inhibitors.
    • If rectal cancer tumour growth blocks the lumen of the rectum, signs and symptoms of obstruction can appear. To prevent this, a stent can be placed in the rectum.
  • Palliative care might be needed in advanced cases of rectal cancer that have a terminal prognosis.
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Prognosis of rectal cancer

If rectal cancer is caught early and treated, the five-year survival rate is nearly 67%. This means that 67% of people who get diagnosed with colon cancer, survive for at least 5 years after that. The prognosis of rectal cancer is minutely better than that of colon cancer. Although the rate of colorectal cancer is declining in older patients, it is on the rise in younger ones, possibly due to lifestyle habits. However, it is important to remember that individual outlook also depends on the extent of spread, size of the tumour, presence of metastasis, general health of the patient and how well they may tolerate treatment.

Medicines for Rectal Cancer

Medicines listed below are available for Rectal Cancer. Please note that you should not take any medicines without doctor consultation. Taking any medicine without doctor's consultation can cause serious problems.