Colorectal cancer
In SA, the most recent National Cancer Registry (NCR) data from 2019 shows 2 338 new cases of colorectal cancer diagnosed in males accounting for 5,63% of all cancer cases.
Most colorectal cancers arise from adenomatous polyps. These polyps are made of excess numbers of both normal and abnormal appearing cells in the glands covering the inner wall of the colon. Over time, these abnormal growths enlarge and ultimately degenerate to become adenocarcinomas.
Screening and symptoms
Symptoms may not be present when you are diagnosed or be minimal and overlooked until they become more severe. Colorectal cancer screening is therefore important to encourage, this can reduce the stage of colorectal cancer at diagnosis and improve survival outcomes.
All average-risk adults aged 45 years and older should undergo regular screening with either a high-sensitivity stool-based test or a colonoscopy every three to five years, based on personal preferences and test availability. As a part of the screening process, all positive results on non-colonoscopy screening tests should be followed-up with timely colonoscopy test.
Special screening programmes are used for those with a family history of colorectal cancer with earlier age for the start of screening.
The most common symptoms are bleeding from the rectum or blood mixed with stool and changes in bowel movement frequency and consistency. Small-calibre (narrow) or ribbon-like stools can also be a sign of a narrowing colon or rectum. If the tumour gets large enough it may completely or partially block the colon or rectum, resulting in abdominal distension or abdominal pain and even perforation of the bowel.
Rectal cancers can result in a sensation of incomplete evacuation after a bowel movement or rectal pain and unexplained weight loss.
Diagnosis
At colonoscopy, a biopsy can be taken and sent to a pathology lab to confirm the tissue diagnosis of a colorectal cancer.
After a confirmed diagnosis is made, various laboratory studies are done with a goal of assessing your organ function, to adequately assess tumour burden and your fitness before a treatment plan can be made.
Adequate imaging of the chest, abdomen and pelvis should be obtained for staging purposes preoperatively.
Treatment
Once you have been adequately worked-up and staged, all patients should be reviewed in a multi-disciplinary team to plan the best way forward for treatment.
Surgery is the only curative modality for localised colon cancer (Stage 1-3). The advent of laparoscopy has revolutionised the surgical approach to colonic resections for cancers.
Surgical resection may be possible in some patients with limited metastatic disease in liver and/or lung (Stage 4), but the proper use of selective metastatic tumour resections needs to be discussed.
Adjuvant (post-op) chemotherapy is standard for patients with Stage 3 disease.
It’s also used in Stage 2 disease for patients with high-risk disease who present with obstruction or perforation.
Chemotherapy rather than surgery has been the standard management for patients with metastatic colorectal cancer. Biologic agents have assumed a major role in treatment of metastatic cases, with selection increasingly guided by genetic analysis of the tumour.
Immunotherapy is indicated for unresectable or metastatic colon cancer that has tested positive for microsatellite instability-high or deficient mismatch repair and has progressed following treatment.
Radiation is of value in the neo-adjuvant (pre-operative) treatment with or without concurrent chemotherapy and the adjuvant treatment of rectal cancer.
There is also a significant role in radiotherapy in some patients for palliative treatment of selected metastatic sites, such as bone or brain metastases, and to reduce bleeding and pain in some rectal tumours.
Although resection is the only potentially curative treatment for patients with colon metastases, other therapeutic options for those who aren’t surgical candidates include thermal ablation techniques.
Survivorship
Several large adjuvant trials showed that 85% of colon cancer recurrences occur within three years after resection of primary tumour, with 95% of recurrences occurring within five years. Therefore, patients with resected colon cancer (Stage 2 and 3) should undergo regular surveillance for at least five years following resection.
Follow-up guidelines:
- A consultation with a history and physical examination every three to six months for three years, then every six to 12 months in the fourth and fifth years.
- A serum CEA, every three to six months for three years, then every six to 12 months in the fourth and fifth years.
- A chest, abdominal and pelvis CT scan every six to 12 months for first three years and then yearly for years four and five.
- A colonoscopy at one year after surgery, and every three to five years thereafter dictated by the findings on the previous colonoscopy.
Colorectal cancer screening is the most significant tool that we have to improve colorectal cancer outcomes. It’s important to highlight and encourage screening tests and colonoscopies which can result in a decline in colorectal cancer incidence and death rates.
Prof Georgia Demetriou is the Academic Head of Medical Oncology at the University of the Witwatersrand, Johannesburg and heads up the Oncology Syndicate of the Wits Clinical Trial Unit. She is the acting Head of the Department of Medical Oncology at the Charlotte Maxeke Johannesburg Academic Hospital as well as a medical oncologist in private practice at the Wits Donald Gordon Medical Centre in Parktown, Johannesburg.
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