What Are the Usual Treatments? Carcinoid Tumors to the Liver
Several treatment options are available for those with carcinoid tumors metastatic to the liver. Deciding among these options involves close communication between the treating physicians and you.
The treatment of choice of all carcinoid tumors is resection of both the primary tumor and all metastatic disease. However, because carcinoid metastases commonly involve both lobes of the liver and may coexist with distant metastatic disease elsewhere, only about ten percent of patients will have disease amenable to curative liver resection. Of the patients who undergo curative liver resection, about three fourths will be alive after five years. Although liver resection is a major operative endeavor, the operative mortality in trained hands is less than three percent.
If the metastatic disease in the liver is too extensive for curative resection, the literature supports palliative (symptom relieving) liver resection if ninety percent of the metastatic tumor burden can be resected. This can lead to symptomatic relief of carcinoid syndrome symptoms, although the duration of the response is thought inversely proportional to the amount of disease remaining after resection. (More disease left, shorter duration of response).
Ablative Therapy
Another palliative choice for treatment of metastatic liver carcinoid is ablation. Cryotherapy involves operative placement of a handheld probe into the parenchyma of the liver under ultrasound guidance. Liquid nitrogen then flows to the tip of the probe, freezing a ball of tissue containing the tumor. No large series have been published documenting survival improvement with this technique, but anecdotal reports have described successful palliation.
Recently, radiofrequency ablation has begun to replace cryotherapy as a palliative measure for metastatic disease. This modality involves intraoperative or percutaneous placement of a probe into the liver near the lesion. Radiofrequency energy is then passed from the tip of the probe, heating the tissue and causing necrosis. Several studies are underway to evaluate this approach.
Hepatic Artery Occlusion/Chemoembolization
These treatment modalities take advantage of the dual arterial blood supply of the liver, receiving blood from both the portal vein and the hepatic artery. Most metastases to the liver have a predominantly hepatic artery blood supply. Ligation of the right or left hepatic artery has resulted in decrease in tumor burden, but results have been somewhat disappointing in that symptoms typically recur.
Embolization is performed in vascular radiology and thus avoids a laparotomy (an open operation). In this procedure, the tumor is directly injected with or without chemotherapeutic agents, (usually doxorubicin with or without streptozocin). Following this, selective particulate embolization (blockage) of the arterial supply of the tumor with gelatin particles combined with ethanol and contrast. Interruption of blood supply has led to reported clinical response rates of up to ninety percent, although most patients eventually succumb to the disease. The role of chemotherapy with embolization is not established and embolization alone has also been found to be effective in treatment of metastatic neuroendocrine tumors.
Chemotherapeutic Regimens
The results of chemotherapeutic treatment of metastatic carcinoid have been variable. Foregut carcinoids have shown the best response rates to streptozocin and cisplatin/etoposide based regimens. However, carcinoids of midgut and hindgut origins are poorly-responsive to chemotherapy, and other options should be explored in these cases.
One option, which has been shown successful in some with midgut carcinoids, is systemic interferon-alpha therapy. Although the mechanism of action of this agent remains unknown, it has led to decline in tumor burden for variable periods of time in patients.
Finally, treatment with radiolabeled MIBG is undergoing evaluation. In this type of therapy, MIBG is complexed to a radioactive compound. Because carcinoid tumors preferentially take up this compound, necrosis-inducing radioactivity is concentrated within them. However, preliminary data has revealed that only fifteen percent of carcinoids respond.
Symptomatic Medical Therapy
Although curative treatment is rarely possible, effective palliation (symptomatic relief) for long periods has been accomplished by combinations of reduction of tumor burden with medical blockade of hormones. Because many of the symptoms are caused by serotonin and tachykinin excess, treatment with the hormone inhibitor octreotide has led to symptomatic relief in over seventy percent of patients. Over time, patients become tolerant to octreotide so that increasing doses are required.
