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FACT SHEET: Colorectal Cancer1 (also known as “large bowel cancer”; includes “colorectal adenocarcinoma”, “carcinoid tumour”, and “gastrointestinal stromal tumour”)

Date of Publication: January 23, 2019

Note: The therapeutic modalities of chemotherapy and radiation therapy are addressed in detail in separate fact sheets.

Is the initiation of non-invasive dental hygiene procedures* contra-indicated?

Is medical consult advised?  

  • Yes, if the patient/client is about to undergo, or is undergoing, radiation therapy.
  • Yes, if the patient/client is undergoing chemotherapy and has, or is suspected to have, certain oral conditions or systemic manifestations. 
  • Yes, if the patient/client is taking a bisphosphonate (either orally or by injection).
  • Yes, if the patient/client appears debilitated.

Is the initiation of invasive dental hygiene procedures contra-indicated?**

  • Yes, if the patient/client is undergoing radiation therapy and/or chemotherapy
  • Yes, if the patient/client has BRONJ (as can be the case in advanced colorectal cancer, depending on treatment).

Is medical consult advised? 

  • See above. Additionally, pre- and post-radiotherapy/chemotherapy medical and/or dental consultation is often warranted. 

Is medical clearance required? 

  • Yes, if the patient/client is undergoing radiotherapy and/or chemotherapy.
  • Yes, if BRONJ exists or is suspected.
  • Yes, if patient/client is being treated with medications (such as corticosteroids) associated with immunosuppression +/- increased risk of infection (e.g., corticosteroids are used as part of some regimens in the treatment of colorectal cancer).

Is antibiotic prophylaxis required?  

  • Possibly, for some patients/clients undergoing radiotherapy and/or chemotherapy according to blood indices and/or delivery mechanism (e.g., in-dwelling central venous catheters or ports).

Is postponing treatment advised?

  • Possibly, depending on blood indices (which indicate degree of immunosuppression and/or thrombocytopenia) in patients/clients undergoing radiotherapy or chemotherapy. Elective invasive procedures should be deferred until after radiation- or chemo-induced immunosuppression ceases.
  • Potentially, if BRONJ exists, informed by medical/dental consultation. Ideally, all necessary invasive dental and dental hygiene treatments should be performed before administration of injectable bisphosphonate drugs.

Oral management implications

  • Refer to also to Radiation Therapy, Chemotherapy, Xerostomia, and BRONJ fact sheets, as applicable.
  • Jawbone metastasis may be the first sign of malignancy. If undiagnosed metastatic cancer of the jaw (or elsewhere in the oral cavity) is suspected, prompt medical referral is indicated for work-up to identify the primary site and to stage the degree of metastatic involvement (i.e., solitary jaw lesion or, more commonly, a clinical sign of disseminated skeletal disease).
  • Oral assessment before, during, and after active chemotherapy and radiotherapy is important. Coordination of care between the oncology and oral health teams is essential for patient/client safety. 
  • Post-operatively, dental hygiene appointments should be kept short as the patient/client deals with fatigue.

Oral manifestations

  • Refer also to Radiation Therapy, Chemotherapy, Xerostomia, and BRONJ fact sheets for details regarding cancer treatment-related dry mouth, caries, mouth sores, gingival bleeding, dysgeusia (unpleasant taste), infections, periodontitis, tooth decay, and osteonecrosis.
  • While cancer metastases to the mandible and maxilla are unusual, about 1% of all malignant neoplasms do metastasize to the jaws2. About 80% of these metastases affect the mandible3, 14% affect the maxilla, and 5% affect both jaws. In adults, the colon and rectum are amongst the most common sources of metastases to the jaws, although lagging lung cancer in men and breast cancer in women. 
  • Persons more likely to be affected by metastatic cancer to the jaws are in the older age brackets, which reflects the higher prevalence of malignancy in this population. The prognosis for patients/clients with metastatic carcinoma of the jaws is poor, with 5-year survival rates in the 10% range.
  • Most metastatic jaw lesions involve one oral site, with only a few occurring in 2 or 3 sites. 
  • Bone pain, tooth ache, loosening of teeth, bone (and hence jaw) swelling, lip or chin paresthesia, gingival mass, trismus, and pathologic fracture may result from metastatic jaw lesions. Radiographically, metastases of bowel cancer typically appear as poorly marginated, radiolucent, osteolytic defects.
  • More rarely, metastatic deposits occur in the gingiva (especially the attached gingiva, with hyperplastic or reactive lesions initially resembling the clinical appearance of pyogenic granuloma4 and periodontal abscess). Metastatic lesions in other areas of the oral soft tissues tend to manifest as submucosal masses, particularly in the tongue, with very occasional presentation as ulcers. 
  • Oral metastases can grow rapidly, causing pain, difficulty in chewing, dysphagia, disfigurement, and intermittent bleeding.
  • Bisphosphonate-related osteonecrosis of the jaw may occur secondary to medications used to manage metastatic cancer affecting the bones. Osteonecrosis may also be caused by metastatic disease itself.

Related signs and symptoms

  • Refer also to Radiation Therapy and Chemotherapy fact sheets.
  • Excluding non-melanoma skin cancer, colorectal cancer (CC) accounts for 12% of all newly diagnosed cancer cases in Canada. Cancer of the large bowel (colon and rectum) is the most common malignancy of the gastrointestinal tract. Annually, about 9,100 persons — slightly more males than females — are diagnosed in Ontario (26,300 in Canada), and 3,150 (9,600) die from the disease. The 5-year net survival rate is 65%.
  • Incidence increases with age, with 90% of persons being diagnosed after age 50 years. Other risk factors include chronic inflammation of the large bowel (particularly ulcerative colitis and Crohn’s disease), high-fat diet, low dietary fibre, and smoking.
  • It can take up to 10 or more years for CC to progress to an advanced stage. Therefore, Cancer Care Ontario recommends either i) screening with the fecal immunochemical test (FIT) every two years for asymptomatic persons aged 50 to 74 years at average risk of developing colorectal cancer,sup>5 or ii) screening with flexible sigmoidoscopy every 10 years for persons at average risk. Colonoscopy screening is recommended for persons at increased risk beginning at age 50 years of age, or 10 years earlier than age first-degree relative was diagnosed, whichever occurs first. 
  • Most cases of CC begin with the development of polyps, which can eventually become cancerous. 
  • Signs/symptoms of CC are bloody stools; abdominal pain and cramping; change in bowel habits (e.g., constipation, diarrhea, and/or narrow stools); unexpected weight loss; loss of appetite; sense of distal colonic or rectal fullness (for left-sided colorectal tumours); nausea and vomiting (if large tumour is present on the right, ascending side of the colon); gas and bloating; and lethargy (if tumour-related bleeding leads to iron deficiency anemia, which is most characteristic of right-sided colon cancers). Presenting signs/symptoms may also include those referable to invasion of adjacent organs (e.g., liver, kidney, or vagina). 
  • For patients/clients with CC, depending on individual circumstances, treatment options might include one or more of: surgical excision; colostomy6; radiation therapy (external beam and/or endorrectal brachytherapy7); and chemotherapy. 
  • Bloating, as well as rectal and bladder irritation can result from radiation to the pelvis. 
  • Nausea and vomiting can result from abdominal irradiation, and diarrhea is common with intestinal radiotherapy. Fecal incontinence is a late side effect of radiation therapy (6 or more months after external beam radiotherapy is completed).

References and sources of more detailed information

Date: December 4, 2017
Revised: January 20, 2020


1 Cancerous cells are characterized by uncontrolled growth, abnormal structure, and the ability to move into other parts of the body (invasiveness and metastasis).
2 The mechanism of spread to the jaws is usually hematogenous (i.e., via the blood stream) from the primary neoplasm or from lung metastases.
3 The premolar region, the angle, and the body of the mandible are most commonly affected by metastatic disease.
4 Pyogenic granuloma is a benign, vascular “overgrowth” lesion that occurs on the mucosa or skin due to irritation, physical trauma, or hormonal factors.
5 Prior to FIT screening implementation provincially in 2019, Cancer Care Ontario recommended the guaiac fecal occult blood test (gFOBT) as the screening test of choice for those at average risk of developing colorectal cancer. FIT offers a number of advantages over gFOBT.
6 A colostomy is a surgical opening made through the abdominal wall to facilitate collection of fecal waste from the colon in an external appliance. While in most cases (following removal of the diseased portion of the colon and/or rectum) the healthy bowel portions are reattached, sometimes this is not possible, and the colostomy becomes permanent.
7 Endorectal brachytherapy for rectal cancer is usually given as a single, high dose of radiation in a very short period of time. After the radiation is given, the applicator or catheter with the radioactive material is removed.

* Includes oral hygiene instruction, fitting a mouth guard, taking an impression, etc.
** Ontario Regulation 501/07 made under the Dental Hygiene Act, 1991. Invasive dental hygiene procedures are scaling teeth and root planing, including curetting surrounding tissue.