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Dr. Praveen Kammar

MS, MRCS, MCH

Surgical Oncologist

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The Difference Between Colon Cancer And Rectal Cancer?

While both illnesses have many similarities, a key difference sets them apart. The differentiation is the origin of cancer. Rectal cancer is defined as cancer that originates in the rectum. The rectum is the terminal portion of the digestive tract and extends for a length of 15 cm when measured from the anal verge. If the origin is farther up the big intestine, it is colon cancer. The colon is the large intestine between the small intestine and rectum.

There are also some differences between the two for treatment. This is because of the location of these organs. The rectum is placed in the pelvis. The pelvis is a tight space where vital organs are close. The nerves that control bowel and bladder function, the blood supply to pelvic organs are very close to the rectum. There is a urinary bladder in front of the rectum in males while the uterus is sitting in front of the rectum in females. Considering this proximity, there is a risk of spread of cancer to these structures in rectal cancer. Hence radiation plays a vital role in the management of rectal cancer.

Surgery plays a key role in the management of both cancers. There is a possibility of having a temporary or a permanent stoma in case of rectal cancer surgery. In contrast, such a possibility is virtually nil in the surgery for colonic cancers unless in emergencies.

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Is rectal cancer more curable than colon cancer?

Mostly, rectal cancer is more challenging to treat, with a recurrence rate between 15 to 45%. In addition, rectal cancer develops in a significantly more congested area than colon cancer because of the latter’s location in the abdomen. As a result, rectal cancer is more likely to spread to other tissues.

How do you diagnose colon and rectal cancer?

Same tests are used to diagnose colon and rectal cancers. 

  • Examining your colon and rectum using a colonoscopy: A long, flexible tube (colonoscope) is used with a video camera and monitor to observe your colon and rectum. If your doctor discovers cancer in your rectum, they may suggest that you have your colon checked to see if there are any more suspect regions.
  • For testing, removing a tissue sample (biopsy): If your doctor finds anything during colonoscopy, he will take a biopsy for further examination. 

Are treatments for colon cancer and rectal cancer the same?

There are major differences in the treatment of these two cancers. The treatment depends on the stage of cancer. Surgery forms a mainstay in the treatment of both cancers.

However, the majority of rectal cancers patients need a combination of radiation and chemotherapy before going for surgery.

It is necessary because the rectum lies in the pelvis and is near several vital organs ( urinary bladder, uterus, nerves, blood vessels). Its not practical to remove these organs to achieve complete removal of rectal cancer with negative margins. Hence radiation helps in downsizing the tumour and sterilizing the field of surgery. This ensures that rectal cancer is removed with negative margins during surgery.

The use of chemotherapy and radiation in rectal cancer also allows dissolving the tumor completely, thus avoiding surgery altogether. Such a complete response happens in 20% of patients.

The role of chemotherapy and radiation before surgery is limited in colon cancer. Before surgery, such a treatment is considered only in colon cancers that have spread to involve other surrounding organs.

The cancers in the middle and lower part of the rectum need special mention. In this region, the blood supply is precarious. And any division of the rectum and rejoining to remove rectal cancer in this area poses a risk of leakage. Hence for cancers of the mid and low rectum, a diversion stoma is almost always needed to prevent the complications of a leakage.

Cancers of the low rectum ( last 5cms ) can involve the entire sphincter mechanism that controls the continence. Whether this sphincter can be saved during surgery and thus preserve the natural passage of stools depends on the extent of the involvement of the sphincter. MRI assessment and presurgery chemo and radiation help in taking this decision. When the sphincter cannot be preserved, the patient lands with a permanent stoma.

Both cancers may have to receive chemotherapy after surgery, depending on the stage.

Is one cancer more serious/aggressive than the other?

When we consider the overall results, both cancers are similar. In localized colon and rectal cancer, 5-year survival is rate is approximately 90%. It drops down to 72 % in the presence of regional spread. Both cancers show 15% survival at 5 years when the distant spread is present.

Conclusion

Both colon and rectal cancer have many similarities, but the origin of cancer sets them apart. Moreover, there is a difference in the diagnosis and treatment of both cancers. If you notice any signs or symptoms related to these cancers, consult an expert today.

With this blog, we hope you don’t have any confusion regarding colon cancer and rectal cancer. You can book an appointment with our expert to know all the information on cancer.

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