It's completely normal to have questions if radiation therapy is part of your treatment plan for colorectal cancer. You may be wondering how it'll affect your body, and what you can expect during your therapy sessions.

Here's how to get ready—both mentally and physically—before your first appointment.

Before your first treatment session, you'll have a simulation appointment to plan your treatment.

You may need imaging tests such a CT scan. You may be asked to drink a contrast dye (contrast agent) like barium, before your appointment. The liquid coats the inside of your stomach and intestines. It helps them to be seen more clearly on a CT scan or X-ray image. You may also have barium put in your rectum through a soft, small rubber tube. In some cases, you may need to drink a liquid contrast dye the day before.

The simulation helps to decide:

• Body position. Your healthcare team will find the best position for you. This might be on your back, stomach, or side. Whatever position your team decides upon, it's for your comfort during treatment and to target the cancer. You may also need to use immobilizers, such as cushions or body molds, to help you hold the exact position needed for treatment.
• Markings and tattoos. Your team may use markings and tattoos to pinpoint the precise location to aim the radiation. The markings can be washed off after treatment. But the tattoos will stay as little dots on your body permanently.

Your body positions and markings will be the same for your entire treatment.

On the days of your sessions, wear loose comfortable clothes and slip-on shoes. This way you can easily change for the treatment.

Inside the treatment room, your radiation will proceed just as it did in your simulation.

1. Your radiation therapist will help you get into position on the table. They may also place blocks or special shields to protect parts of your body that don't need radiation.
2. Your therapist will line up the machine with the marks or tattoos on your body. You may see lights and laser lines come out of the machine and align with those marks. This confirms you're in the right position. You will need to not move. You must stay in position until the treatment is done.
3. Your therapist will leave the room and start the machine. You may hear whirring and buzzing, or even see the machine move. But don't worry—it won't touch you and it doesn't hurt. If you have concerns, your therapist can see you, hear you, and talk with you.

The treatment sessions often take only a few minutes. It's completely painless and you won't be radioactive after. You can head home once your session is over.

Like any treatment, you may have some side effects after treatment. This is because radiation sometimes kills healthy cells in addition to cancer cells. Keep in mind that side effects may be different for each person. Sometimes you may not even have any. Or some side effects occur after several treatments. Talk with your healthcare team about what you might experience. Make sure you know what to expect and when to report any side effects.

Some short-term side effects to look out for include:

• Diarrhea or loose poop
• Gas and bloating
• Nausea
• Feeling the need to pee often
• Pain or burning feeling when you pee or poop
• Blood in your poop
• Trouble controlling your bowel movements
• Severe tiredness (fatigue)
• Low blood counts on blood tests
• Skin irritation or skin changes in areas that get radiation

These side effects may sound uncomfortable. The good news? Most can be managed. Be sure to share with your healthcare team if you have any side effects. Ask them about when you should be more concerned so you can watch them.

Keep a side effects diary. This diary should include the side effect, what time of day you feel it, how long it lasts, and if it happens more than once. Also write down any questions you have for your healthcare team. This can help them find the best solutions for you.

Most side effects can be managed through medicine and diet. And they often improve over time once your treatment ends. But some may also last longer.

After treatment, you may also have some long-term effects. These can also show up months or years later. This will depend on where and how much radiation you received. These side effects may or may not become more serious. Be sure to watch for them and talk with your healthcare team about what to expect.

Keep an eye out for these long-term side effects:

• Bowel or bladder changes. You may notice changes in your bowel movements or bladder. This includes looser poop, blood in your poop or pee, loss of bladder control, or having to go to the bathroom more often. You can sometimes manage these symptoms by making changes to your diet or taking medicine. Talk with your healthcare provider to learn your best option.
• Early menopause (hormone changes) or infertility (inability to become pregnant). If you are planning on having children, discuss your choices with your healthcare team before starting radiation treatments. There may be things you and your providers can do to help preserve your fertility. If you're a woman who hasn't gone through menopause, you may have menopausal symptoms such as hot flashes, vaginal dryness, and not having your menstrual period. Talk with your provider about what you can do to ease your symptoms.
• Vaginal dryness. Women may have vaginal dryness and narrowing and shortening of the vagina. This can lead to pain or bleeding during sex. To help, try vaginal lubricants. You can also try stretching the vagina by having sex or using a vaginal dilator. Your provider can talk with you about types of lubricants and where to find a dilator and how to use it.
• Lower sperm count. Following treatment, some men may produce less semen. Or their semen could have a lower sperm count. While this can affect fertility, it's still possible to get a partner pregnant. Talk with your provider about fertility treatments. If you know you might want children in the future, ask about saving sperm before you start radiation treatments.
• Erectile dysfunction. Men may have trouble getting or keeping an erection after treatment, especially if they had trouble before. If this happens to you, don't be embarrassed to talk with your provider. This symptom can be managed through medicines or a penile pump.