Radiation Therapy for Gastrointestinal Carcinoid Tumors

Radiation therapy is the use of high-energy rays (such as x-rays) or radioactive particles to kill cancer cells.

Although surgery is the main treatment for most carcinoid tumors, radiation therapy may be an option for those who can’t have surgery for some reason. It may also be given after surgery in some cases if there’s a chance some of the tumor was not removed. Radiation therapy can also be used to help relieve symptoms such as pain if the cancer has spread to the bones or other areas.

External beam radiation therapy (EBRT)

External beam radiation therapy uses a machine to deliver a beam of radiation to a specific part of the body. This type of radiation is used most often to treat cancer.

Side effects of gastrointestinal (GI) radiation therapy

The main side effects of GI radiation therapy are:

• Tiredness (fatigue)
• Nausea and vomiting
• Diarrhea (if the belly or pelvis is treated)
• Skin changes, which can range from mild redness to blistering and peeling
• Hair loss in the area being treated

Procedures using radioactive drugs

Radioembolization

This technique combines embolization with radiation therapy and is used to treat liver metastases.

Embolization is a procedure that injects substances to try to block or reduce the blood flow to cancer cells in the liver. The liver is unusual in that it has 2 blood supplies. Most normal liver cells are fed by the portal vein, whereas cancer cells in the liver are usually fed by the hepatic artery. Blocking the branch of the hepatic artery feeding the tumor helps kill off the cancer cells, but it leaves most of the healthy liver cells unharmed because they get their blood supply from the portal vein.

In this procedure, a catheter (a thin, flexible tube) is put into an artery through a small cut in the inner thigh and eased up into the hepatic artery in the liver. A dye is injected into the blood at the same time to allow the doctor to monitor the path of the catheter via angiography, a special type of x-ray. Once the catheter is in place, small particles called microspheres are injected into the artery to plug it up.

In radioembolization, microspheres (small beads) that are attached to a radioactive element called yttrium-90 (or 90Y) are used. After they are injected, the beads travel in the liver blood vessels until they get stuck in small blood vessels near the tumor. There they give off radioactivity for a short while, killing nearby tumor cells. The radiation travels a very short distance, so its effects are limited mainly to the tumor.

Peptide receptor radionuclide therapy (PRRT)

In this form of radiation therapy, a drug is linked to a radioactive element. The drug travels throughout the body, attaches to the cancer cells, and gives off radiation to kill them. It is given through a vein and not directly into the liver like radioembolization. 

One option is to use somatostatin analog drugs like octreotide or lanreotide linked with a radioactive form of the element yttrium-90. Another option uses a different radioactive element, called lutetium (Lu-177), that is carried to the cancer cells by dotatate where it attaches to carcinoid tumor cells. These injectable therapies let doctors deliver high doses of radiation directly to the tumors. 

For adults with somatostatin (a type of hormone) receptor-positive GI carcinoid tumors, that are no longer responding to octreotide or lanreotide, a radioactive drug, called Lutathera (lutetium Lu- 177 dotatate), can be used for treatment. Lu-177 dotatate, also called a radiopharmaceutical, works by attaching to the somatostatin receptor (protein), which is part of the cancer cell, allowing radiation to enter the cell and cause damage. If you are taking octreotide or lanreotide, you will most likely be asked to stop taking these medicines before Lu-177 dotatate is given.

Common side effects of Lu-177 dotatate include low levels of white blood cells, high levels of enzymes in certain organs, nausea and vomiting, high levels of blood sugar, and low levels of potassium in the blood.

Serious side effects of Lu-177 dotatate include low levels of blood cells, development of certain blood or bone marrow cancers, kidney damage, liver damage, abnormal levels of hormones in the body, and infertility. Women who are pregnant or might become pregnant should be advised that Lu-177 dotatate can cause harm to a developing fetus.

Lu-177 dotatate is given intravenously and does expose those taking it and possibly others around them to radiation. Family members should know how to protect themselves from being exposed to the radiation.