Ask a Doctor : Q&A on Radiotherapy

Left: Laura A. Dawson, MD, FRCPC, Princess Margaret Cancer Centre/University Health Network, University of Toronto, Toronto, ON, Canada. Right: Marissa Sherwood, BSc, MD, University of Toronto Department of Radiation Oncology, Toronto, ON, Canada.

1. What is radiotherapy and what are the main types? (internal, external, radioembolization, brachytherapy)

Radiation treatment or radiotherapy, damages cells in a way that stops them or makes it difficult for them to duplicate. Cells duplicate and multiply constantly – cells are what our bodies and organs are made of. The body has a set of rules for cells – mainly when and for how long they can keep duplicating and growing, and there are limits for each one. Cancerous growths or tumors can happen when cells do not follow these rules and duplicate without limits, which leads to uncontrolled growth beyond where the cells usually reside and possible spread to other organs.

There are different ways to deliver ionizing or damaging radiation to treat cancer. The most common type is external beam radiation therapy (EBRT). You can think of this treatment as high energy x-rays that are made with a special treatment machine – the x-ray beams are made from inside a machine and are sent out in a targeted way at the patient and more specifically, the part of the patient where the cancer is. When radiation treatment is happening, a person lies on a treatment table and the radiation machine moves around them – it looks like getting a CT or CAT scan. During radiation, you cannot see, feel, smell, or hear the x-ray beams. You do not feel burning, and you are not radioactive or dangerous to other people from this treatment. This type of radiation usually happens once a day, for 5 days a week (Monday to Friday) over at least 3 weeks. Stereotactic radiation therapy (SBRT) is a specific type of EBRT, that delivers high doses very precisely around the tumor, with a very high chance of tumor ablation/eradication.

Another type of radiation treatment is called brachytherapy or internal radiation. This is different than external beam radiation. In external beam as described above, x-rays come from outside the patient from a machine and are targeted at the person. In brachytherapy, a radioactive object or source, is placed inside the person to give a high amount of radiation to a very specific spot. Examples of this are in treating cancers of the cervix or prostate, where radiation can be placed directly on the sites of cancer from inside the patient. Rarely brachytherapy is used to treat rectal cancers.  In some cases, the radiation stays in the patient forever and gives a small amount of radiation every day (e.g., radioactive beads); in other cases, the radiation is in the patient temporarily and is then removed. Internal radiation has more safety rules for the patients in the short term after their treatment.

A third type of radiation treatment is radiopharmaceuticals, which include drugs that contain radioactive isotopes.  An example is Yttrium-90 that is delivered to the liver through the hepatic artery to treat liver metastases.

2. What is it used for? i. rectal cancer, ii. colon cancer, iii. other organs?

Radiation can be used, in some way, for every type of cancer. It can be used to cure cancer on its own, or combined with other treatments like surgery and chemotherapy, and it may be used in place of surgery with the goal of preserving organ function, e.g., anal canal chemo-radiation, reserving surgery for salvage if the cancer recurs. It can also be used to manage pain or other symptoms caused by cancer, such as bleeding or swelling.

3. When would a patient require radiotherapy? i.e., before, during, after surgery.

Some terms a patient might hear about the timing of radiation treatment are “definitive, neoadjuvant, adjuvant, concurrent or palliative”. Definitive radiation means it is the main treatment that is typically done first and may be the only treatment a patient needs. Neoadjuvant radiation means it is delivered before another treatment, such as radiation before surgery or chemotherapy starts. Adjuvant radiation means the radiation is delivered shortly after another treatment finishes. Concurrent radiation means it happens together, at the same time, as another treatment, to help both treatments work better together; it is common for radiation therapy to be delivered concurrently with chemotherapy such as capecitabine. The terms neoadjuvant, adjuvant or concurrent mean the radiation is part of a combination of treatments that work best when delivered together as an overall treatment plan. Palliative radiation means the radiation is being delivered to help treat symptoms – this type of radiation is not intended to cure or get rid of cancers completely.

For colorectal cancers specifically, each patient, depending on the information about their cancer, will require different treatments at different points in time. Many patients with localized rectal cancer are recommended to receive radiation therapy in addition to other therapies to reduce the risk of the cancer returning. Radiation is used less commonly to treat local colon cancer. SBRT is being used more commonly to treat isolated or few sites of metastatic cancer, e.g., in the liver or lung or nodes.

4. How is it used? Alone or in combination with chemotherapy?

Radiation can be used alone and in combination with chemotherapy, depending on the type of cancer being treated, how advanced the cancer is and what the goals of treatment are (i.e., is this to get rid of the cancer, or to help more with symptoms?)

5. What are the criteria for receiving radiotherapy? 

There are some reasons why a patient may not be able to get radiation, or it may be more complicated to receive it. These reasons include if a patient is pregnant, if they have had radiation treatment in the past, if they have certain diseases such as lupus, scleroderma or Sjogren’s, if they have a pacemaker or if the person cannot lie flat or still enough for treatment.  None of these reasons are absolute contraindications for treatment, but they all make it more complicated to deliver radiation in a safe way. 

6. What are the possible side effects and how can we reduce them?

A good way to think about side effects from radiation are splitting them into short- and long-term side effects. Short term side effects are those that occur during or shortly after a person is getting radiation (e.g., within 3 months) while long term side effects can happen months to years later.

Common short term side effects for radiation in the lower abdomen or pelvis, are feeling tired, having more frequent bowel movements, and passing urine more often, having irritation with going to the bathroom (i.e., some burning with passing urine, having diarrhea), more gas, and possibly some nausea. During radiation treatment, each patient has an appointment every week with the radiation doctor to monitor for side effects and help manage them with medications (like Gravol or Imodium) or changes to diet to help with bowel movements for example. These short-term side effects tend to get worse towards the end of radiation treatment – so if, for example, a patient is getting 25 daily treatments, they usually have more side effects in the last few weeks and even for a few weeks after the radiation finishes. The radiation keeps working in the body even after the last treatment has finished.

Long term side effects include permanent changes in a person’s bowel or bladder function – patients may permanently go to the bathroom a bit more often than they did before radiation. The odds of needing a medical treatment or surgery for a severe problem in the bowel or bladder is very rare. People may also notice their skin may become a bit darker, with hair loss and different skin texture in area where skin was irradiated. For all patients, we also consider a very small risk of a second cancer occurring within the radiated region of the body, that may occur many years or decades after radiation therapy is delivered.  A general rule of thumb is that after someone has received radiation treatment, their chance of a second cancer being cause by the radiation is about 1% higher after 10 years than someone of the same age who didn’t get radiation.  It is important for patients with a prior cancer and prior radiation therapy to have healthy lifestyles, e.g., not smoke or use alcohol excessively, and receive vaccines, to try to reduce the risk of subsequent cancers and long-term side effects.

7. We have heard about Watch and Wait management for rectal cancer. How does radiotherapy fit into this management strategy?

“Watch-and-wait” strategy is a non-invasive treatment approach for selected patients with rectal cancer who have had a complete response after radiation therapy and chemotherapy. Surgery is omitted in this strategy, reserving it for patients who develop a recurrence. This approach requires regular and frequent imaging and scopes to monitor the rectum. This strategy is promising for patients with early rectal cancers; however, it is not ready for routine practice.  It is offered on clinical trials to investigate the long-term clinical outcomes of this strategy in comparation to surgical resection that remains the standard of care.

8. Are there any trials in this area that might be of interest to colorectal patients?

There are many clinical trials for colorectal cancer patients, and it is always recommended to ask about open trials when deciding on treatment options. In Canada today (December 2021), there are trials of “watch and wait” radiation therapy for selected patients with rectal cancer. There are also trials of SBRT for patients with 1-10 metastases. Trials open and close often, so it is important to ask your oncologist about what is open. A good web reference for finding open trials in your location is clinicaltrials.gov.