Microsphere management of liver mets gains strength

Radioactive microsphere therapy is gaining in popularity among specialists who deal with both primary and metastatic solid tumors in the liver. During the past two years, sessions dedicated to this therapeutic approach have been held in meetings of all major related specialties: interventional radiology, radiology, radiation oncology, surgical oncology, hepatobiliary surgery, nuclear medicine, and medical oncology.

With more than 6000 patients treated in the U.S. alone in the past three years, a significant body of peer-reviewed literature has been published to aid in understanding how and in which patient population to use this treatment, particularly yttrium-90 microspheres.

Key issues in 2007 have been refinement of patient selection and expansion of treatment to a variety of histologic tumor types. Major successes have been achieved in breast cancer metastases, cholangiocarcinoma, neuroendocrine metastases, and ocular melanoma. Several multi-institutional clinical trials and dedicated quality of life studies have either started or are expected to be completed soon in neuroendocrine, colorectal, and hepatocellular cancers.

None of this research or treatment application would be possible without a multidisciplinary approach that incorporates the latest in imaging technology to localize tumors, evaluate extent of disease, assess the safety of future microsphere treatment, and confirm treatment success. The following pictorial demonstrates how imaging is used in microsphere therapy.

PET imaging greatly assists in treatment planning and assessment of response in a large number of different tumor types affecting the liver in patients receiving radioembolization. Researchers at the Third Annual Symposium on Liver-Directed Microsphere Therapy presented compelling pretreatment and post-treatment PET scans of patients who received internal radiotherapy for unresectable and chemorefractory tumors from breast, colon, bile duct, pancreatic, esophageal, neuroendocrine, and melanoma cancers. The general conclusion was that PET was more reliable than CT in gauging response.

METASTATIC NEUROENDOCRINE CANCERS IN LIVER

Carcinoid tumor in the liver treated with microspheres has demonstrated excellent response and reversal of clinical symptoms. The effects of internal radiotherapy are apparent in these images, with overall liver healing accompanied by a change in contour and volume of segments. This is due to a combination of parenchymal retraction during fibrotic healing and hypertrophy of unirradiated healthy liver immediately adjacent to the tumor deposits.

The patient experienced 70% reduction in his serum tumor marker value and significant reduction in carcinoid symptoms after a single microsphere treatment. He ultimately died of distant metastatic disease but did not experience liver dysfunction over his 2.5-year survival after radiation. He had been treated with chemotherapy and Sandostatin prior to radiotherapy (Kennedy, Warner, Dezarn, et al. Manuscript in press, presented at the North American Neuroendocrine Society Annual Meeting, Sept. 26, 2007).

HEPATIC METASTASES FROM OCULAR MELANOMA

Ocular melanoma is unique in that it almost always metastasizes only to the liver, which in turn is the most common reason for patient death, as so few treatment options are available. Chemotherapy is ineffective, and the disease is typically spread throughout the liver, excluding surgical removal or external-beam radiation therapy. Internal radiotherapy with yttrium-90 microspheres has demonstrated consistent and useful tumor reductions. (Kennedy, Nutting, and Dezarn; manuscript in press)

This patient, who presented with right uveal cancer (A) and synchronous liver metastases (B), had a complete response within six months of microsphere treatment in the liver (C), which contained persistent cancer despite 13 prior transcatheter arterial chemoembolization procedures. The ocular tumor was treated surgically.

Dr. Kennedy is a radiation oncologist and co-medical director of Wake Radiology Oncology in Cary, NC.