Multidisciplinary Treatment of Pancreatic Neuroendocrine Tumors - Episode 8
Liver-directed localized treatments are usually delayed until patients with pancreatic neuroendocrine tumors (pNETs) are no longer candidates for systemic treatment, states Rodney Pommier, MD. It is important to consider the size and location of the tumor in the liver, adds Pommier. The liver needs to be safely accessed without hurting major bile ducts and hepatic arteries whose damage may jeopardize liver tissue that should be preserved.
Surgery is an option, if the tumor involves less than 50% of the hepatic parenchyma, leaving the remaining as viable liver that can be protected, says J. Philip Boudreaux, MD. If more than 50% of the liver is involved with the tumor, that patient may not be a good candidate for surgery, except in the case of functional tumors, which cannot be controlled in any other way.
Liver-directed therapy options include bland embolization, where the hepatic arteries are occluded, chemoembolization, and radioembolization. There are no data that support chemoembolization being superior to bland embolization, and toxicities are comparable between the procedures, notes Pommier. It is important to remove the gall bladder of individuals when possible, as this will help if they move on to embolic therapy, says Pommier.
Radioembolization utilizes glass or resin microspheres that descend to the capillary level. Yytrium-90 is a beta-emitter with a half-life of about 64 hours that emits high-energy electrons across a short distance. Radioembolization is not occlusive, and patients can have 2 or 3 different cycles that are spaced a few years apart. It is unknown whether responses in the second or third cycle will be as durable as the first cycle, says Pommier.
The utilization of radioembolization is beginning to decline in favor of fractionally embolizing the liver, states Boudreaux. Patients with pNETs are getting better and living longer, but some are dying of radiation-induced cirrhosis and non-cancer related problems.
Peptide receptor radionuclide therapy, or PRRT, combines octreotide, a somatostatin analog, with a radioactive substance. PRRT radiates short distances, sparing the rest of the body. Patients are monitored for a few days, and treatment can be repeated approximately 6 weeks later, explains Pommier.