Targeted therapy and Other Drugs for Gastrointestinal Neuroendocrine Tumors

Targeted drugs work differently from standard chemotherapy (chemo) drugs. These drugs target specific parts of cancer cells.

The targeted drugs used to treat GI neuroendocrine tumors block angiogenesis (the growth of new blood vessels that nourish cancers) or other important proteins in cancer cells that help them grow.

Targeted therapy drugs for GI neuroendocrine tumors

Cabozantinib (Cabometyx)

Cabozantinib blocks several tyrosine kinases (such as RET, MET, and VEGFR2), enzymes that help the tumor grow and divide, and can help slow tumor growth in different ways. This drug is a pill taken once a day.

The most common side effects are nausea, vomiting, diarrhea, constipation, fatigue, poor appetite, and high blood pressure. Rare, but serious side effects include bleeding, clotting, severe high blood pressure, palmar-plantar erythrodysesthesia (PPE, which is redness, pain, and skin peeling of the palms of the hands and the soles of the feet), liver damage, difficulty with wound healing, and harm to a fetus.

Everolimus (Afinitor)

Everolimus blocks a protein known as mTOR, which normally helps cells grow and divide. Everolimus has been shown to help treat advanced GI neuroendocrine tumors. Everolimus is a pill taken once a day.

Common side effects of this drug include mouth sores, infections, loss of appetite, diarrhea, tiredness, cough, and increases in blood sugar levels. A less common but serious side effect is damage to the lungs, which can cause shortness of breath (dyspnea) or other problems.

Other drugs for GI neuroendocrine tumors

Somatostatin analogs

Somatostatin analogs are man-made compounds similar to somatostatin, a natural hormone in the body. They can help slow the growth of neuroendocrine tumor cells. They can be very helpful for patients with GI neuroendocrine tumors that have somatostatin receptors. When somatostatin analogs bind to the somatostatin receptors on cancer cells, they may stop the cancer cells from releasing hormones into the bloodstream. This can often relieve symptoms and help patients feel better. These analogs also seem to help slow the growth of some tumors.

They are very useful for people who have carcinoid syndrome.  Symptoms of carcinoid syndrome include facial flushing, diarrhea, wheezing, and rapid heart rate.

• Octreotide (Sandostatin): One version of octreotide is short-acting and is injected 2 to 4 times a day under the skin. There is also a long-acting form of the drug (called Sandostatin LAR Depot) that only needs to be injected into a muscle every 4 weeks. Depending on the severity of symptoms, some people are given injections every day when first starting treatment. Once symptoms are controlled, the longer-acting monthly injection may be used. Other times, the long-acting drug may be started from the beginning.
• Lanreotide (Somatuline Depot): This is a long-acting somatostatin analog. Most often, it is given every 4 weeks, by injection under the skin. Occasionally, your doctor might recommend this injection every 2 weeks.

These drugs may be given by your doctor or nurse, or you may learn to give the injection at home.

Possible side effects of somatostatin analogs

The main side effects of these drugs are pain at the injection site, and rarely, stomach cramps, nausea, vomiting, headaches, dizziness, and fatigue. These drugs can also cause sludge to build up in the gallbladder, which can lead to gallstones that usually do not cause symptoms. They can also make the body resistant to the action of insulin, which can raise blood sugar levels and make pre-existing diabetes harder to control.