Rectal Cancer Radiotherapy

Colorectal cancer can be screened for with a stool sample. A positive test for blood in your stools will need further investigation, for instance a colonoscopy. Symptoms may not turn up in the early stages of bowel cancer, hence it is important to keep up regular screening for this cancer. It is curable if caught early. Some symptoms you may experience include: visible blood in your stools, even if you have a history of hemorrhoids, altered bowel habits, abdominal pains and weight loss. Do speak to your family physician about your concerns and seek a check for bowel cancer.

If you have a colonoscopy, a biopsy can be performed for any suspicious masses in your rectum or bowel including polyps. If these tissue samples are cancerous, you then need scans to assess the extent of the bowel cancer and if it has already spread into nodes in the pelvis and elsewhere, and also if it has gone into the blood stream and lodged in other organs such as the liver. These scans can include an MRI scan of the rectum and a CT scan of the body. Once you’ve had the relevant tests and cancer presence has been confirmed, your situation will usually be reviewed comprehensively in a tumour board meeting and a treatment plan reviewed. The best chance of cure is when the bowel cancer is still localized and has not spread out.

The rectum is the lower portion of the colon and is above the anal canal. High rectal cancers whose lower edge is more than 12 cm above the anal verge or above the anatomical structure called the peritoneal reflection in the pelvis, generally do not require radiotherapy but in some situations, you may need chemotherapy.

Early rectal cancer, which is staged T1 or T2 does not usually require radiotherapy but in select cases it may be done as well. An example of a situation like this is where the rectal cancer is close to the anal canal and your surgeon is unable to give you a sphincter sparring operation. Radiotherapy may help reduce your likelihood of requiring a permanent diversion of your stools into a bag called a stoma. Another instance where radiotherapy may be recommended for early rectal cancer is when there is doubt it can be successfully removed with negative margins with an operation as your only treatment.

There is an established role for the use of radiotherapy in advanced rectal cancer. However, in some situations, an operation to divert stool passage is undertaken before radiotherapy. This is because bulky rectal cancers may have already or may soon obstruct the passage of stools. Hence, an operation to bypass the rectum and divert the stools to be collected into a stoma bag on the abdomen is sometimes required as the first step in your treatment.

There are some possible pathways where radiotherapy is utilised in recommended treatment plans for localised rectal cancer. The treatment paradigms for metastatic rectal cancer or stage 4 rectal cancer are complex and this requires a more in depth look into each specific situation. Patients should discuss this with their clinician.

The definitive treatment of advanced rectal cancer is still an operation. There are different types of these operations which should be discussed with the surgeon. However, the best outcomes are achieved with combination treatments. These combinations include surgery, radiotherapy and chemotherapy. The optimal type of combination therapy, including duration of radiotherapy, types of chemotherapy, and sequencing with the operation have been and are still being evaluated. This is a dynamic area. In some very fortunate individuals, surgery is not required after some of these combination therapies due to a complete response. This means there is no sign of the tumour after radiotherapy and chemotherapy.

There is acceptance within the oncology field that radiotherapy before and not after an operation is ideal. This has been found to be associated with less side effects. In terms of duration of radiotherapy, there is a 5-week version with 25 treatments. This is done in combination with a chemotherapy drug given daily while undergoing radiotherapy. This is called the long course.
There is also a 1-week version of 5 treatments, this is not done concurrently with chemotherapy. This is called the short course.

Both the long course radiotherapy and short-course radiotherapy are recommended equally. There is high-quality evidence for similar effectiveness and side effects affecting quality of life from patients who have had the 2 different types of treatment. Discuss with your surgical and oncology doctors which approach has been recommended for you.

This approach of either long course (5 weeks RT with chemotherapy) or short course (1 week RT and no chemo) prior to an operation is still the standard of care for stage 2 and 3 rectal cancers. These approaches make your operation more successful in that it reduces the likelihood of the tumour coming back or recurring where it used to be. It also shrinks the tumour, sterilises the involved glands or nodes within the pelvis and as mentioned before, it has lower side effects than post operative radiotherapy. Depending on the results of the surgery, there may be a need for further chemotherapy as well.

There has been emerging evidence that adding more chemotherapy before the long course or short course may be an even better approach. This is called Total Neoadjuvant Therapy (TNT). 2 mains studies called the RAPIDO and the PRODIGE 23 have reported these results and have found that using TNT, the complete response rate doubles. There is also reduction in the risk of it coming back within the reported 3 years and also reduced chance of it metastasising. The additional chemotherapy prior to the operation is also better tolerated than having more chemotherapy after an operation. It is important to note that at least for now, TNT does not give you a better chance of surviving your bowel cancer compared to the standard long course and short course. The role of TNT will be more established with the passage of time as more data emerges.

Preparation for the radiotherapy, whether the long course or short course, is the same. You will need a planning session and will likely need to have a full bladder as well for the CT simulation scan. There may be other steps as well in this planning session. Your radiation oncologist and radiotherapy team will then customise a radiotherapy treatment plan based on the tumour location and where it can spread within the pelvis. Depending on your treatment plan, radiotherapy may be sequenced with chemotherapy as well. Treatment is delivered on an outpatient basis but depending on side effects, sometimes a period of inpatient stay is required. Once treatment is completed, then the next phase is a period of rest and recovery. The tumour during this time may also start to respond. Once adequate time has passed, there may be further scans to evaluate the response and a date for surgery will be planned. A decision may be made also either before or at the time of surgery if you can undergo sphincter sparring surgery.

There can be a number of side effects from the radiotherapy itself. Some of these can be compounded by the chemotherapy as well. For instance: fatigue, diarrhoea, urgency, pain, peeling of the skin around the anal region, nausea and vomiting. Your bladder may also become more irritable and you may pass urine more often with discomfort as well. A number of these side effects will subside with time. There can however be ongoing side effects as well such as faecal urgency and incontinence, altered bowel habits, sexual dysfunction, impaired fertility, and premature menopause. Radiotherapy can sometimes add to the risks of bowel obstruction and may also result in a stiff bladder that has a reduced capacity for urine. Bony injuries to the pelvis and hips can occur rarely and then to do so many years post treatment if at all. Similarly, radiotherapy can cause another cancer in the pelvis, but again it is rare and may take decades to turn up if at all.

Once you’ve had your operation, the pathologist will examine the rectal tumour that has been removed and assess how successful the down staging has been and if there are negative margins successfully achieved by the surgery. Based on the presence of tumour cells in the nodes, a recommendation may be made for chemotherapy. Ongoing surveillance is required as well as part of your ongoing reviews.

© Ramesh Pandey March 2025