QUESTION: OK, I think I understand external radiation therapy. How is internal radiation therapy planned?
ANSWER: Internal radiation therapy is also commonly known as “brachytherapy.” Internal radiation uses radiation sources that are implanted into a tumor. Internal radiation therapy is most commonly used for prostate cancer, gynecological cancers (specifically, endometrial or cervical cancer), and certain breast cancers.
For internal radiation therapy to work, we need to implant the radioactive source(s) inside of you, either for a few minutes (called high dose rate (HDR) brachytherapy), or permanently (called low dose rate (LDR) brachytherapy).
The first thing we do is a CAT scan, ultrasound, or MRI of the tumor to help find out how large it is.
QUESTION: Why not just use high dose rate (HDR) brachytherapy instead of low dose rate (LDR) brachytherapy? Won’t my dose be higher?
ANSWER: Similar to the brick wall analogy of external beam radiation therapy, the total dose, or the “size of the wall” is the same between HDR and LDR brachytherapy.
QUESTION: Am I awake during the radiation?
ANSWER: It depends on the type of tumor being treated. If we are treating prostate cancer, the patient is asleep. If we are treating endometrial cancer, the patient is awake. For cervical cancers, the patient may be sedated. You should speak to your doctor for more details.
QUESTION: Does internal radiation therapy also pass through my body like external radiation?
ANSWER: Remember how we said external radiation is like a flashlight? Internal radiation is like a very small candle: it is strong near the wick, but it becomes very weak the farther away you move from it. We need to position dozens of tiny radioactive sources, which are like small candles, inside of or near the tumor to kill the cancer cells. Don’t worry, there is no “fire” or “burning” — it’s similar to external radiation.
QUESTION: What is low dose rate brachytherapy?
ANSWER: Low dose rate brachytherapy is also called a “permanent seed implant” or “seed implant.” It is most commonly used for prostate cancer. These seeds are different than the ones we mentioned to help guide external radiation. These radioactive seeds are positioned in the prostate and give off their dose over many months to a volume. Think of it like a “cloud” of radiation covering the prostate. We only need to do this seed implant procedure once.
QUESTION: What is high dose rate brachytherapy?
ANSWER: High dose rate brachytherapy is called a “temporary implant.” We first position catheters inside or near the tumor. Next, a highly radioactive source travels through the catheters and delivers a dose of radiation to the tumor. We can fill the area where cancer cells are located with a radiation cloud. For the temporary implant, we need to do the procedure typically a few times. The procedures are typically one week apart.
QUESTION: What does internal radiation therapy feel like?
ANSWER: Similar to external radiation therapy, with internal radiation therapy, you don’t see anything. You don’t feel anything. You will not glow after the treatment. You will not lose the hair on your head. You will not be a danger to anyone. You will not set off alarms or bells in the airport
Side effects from internal radiation therapy may be present after weeks, months, or years. The side effects of internal radiation depend on the normal organs that are near the tumor. You should talk to your doctor about what side effects to expect after your treatment.
QUESTION: Can you see the tumor dying?
ANSWER: Just like external radiation, internal radiation is like putting money into an investment account: we don’t see anything after weeks or sometimes even months. The radiation effects occur over many months even after the treatment is complete. Thus, we cannot see tumors dying during treatment, and we don’t take any pictures at the time of the procedure to check. We will tell you what tests to get after you finish the treatment.
QUESTION: May I continue sexual activity during or after internal radiation therapy?
ANSWER: Since most internal radiation therapy is used for cancers near the pelvis (for example, prostate, uterus, and cervix), it is difficult to say when you would be ready for sexual activity. You should talk to your doctor for more details.