Oct. 1, 2003 A new study shows that molecular analysis of a very small tissue sample can identify hidden melanoma metastases in lymph nodes. The presence of melanoma in the lymph nodes is the single most important factor in determining a patient's prognosis and is a key factor in determining a patient's course of treatment.
Published in the October 1 issue of the Journal of Clinical Oncology, the study is the first to use such a thin section of archival paraffin-embedded tissue and show that a specific set of molecular characteristics indicates the presence of melanoma in the lymph nodes – even among patients whose lymph nodes appear cancer-free using standard techniques. By using a small tissue section, pathologists spare more of the whole specimen, which is needed for additional pathology tests.
"Our findings show that by performing molecular analysis on a very small piece of tissue, we can quickly and accurately identify previously undetectable metastases, and provide a more accurate prognosis for patients," said Dr. Dave S.B. Hoon, director of the Department of Molecular Oncology at the John Wayne Cancer Institute in Santa Monica, California, and senior author of the study. "Providing a more accurate prognosis can inform decisions on when and how to treat patients, and could ultimately improve our ability to care for patients with melanoma."
Dr. Hoon and his team designed a molecular test to detect the presence of four melanoma-associated proteins, or "markers," in lymph node tissue. They obtained archived tissue samples from 77 patients. Standard tests revealed that 37 of the samples contained melanoma, indicating a poor prognosis. However, using the new molecular analysis, researchers showed that the lymph nodes of 25 percent of the 40 patients whose nodes were thought to be cancer-free actually contained two or more of the melanoma-associated markers.
Researchers then observed all patients for nearly five years to determine if there was any correlation between the number or type of melanoma markers and patients' clinical outcomes. They found that patients with two or more of the markers were more than twice as likely to develop a recurrence of their disease than patients whose lymph node samples presented zero or one marker, and were nearly five-times as likely to die as a result of recurrence.
"Our study is the first to show that patients who express these specific melanoma markers are much more likely to have a poorer outcome, which has wide-ranging implications for the type and extent of treatment that they receive," said Dr. Hoon. "In addition, we are able to identify these patients using a previously-archived tissue sample, sparing the remainder of the valuable whole tissue specimen for other tests."
Dr. Hoon and his colleagues are in the process of enrolling patients in larger clinical trials that will examine the use of these and other markers to better detect melanoma in the lymph nodes, which could dramatically improve the accuracy of diagnosis and identify patients who would benefit from stringent monitoring and preventive therapy.
"Prediction of Disease Outcome in Melanoma Patients by Molecular Analysis of Paraffin-Embedded Sentinel Lymph Nodes." Christine Kuo, M.D. et al.; John Wayne Cancer Institute, St. John's Health Center, Santa Monica, CA. Vol 21, No 19 (October 1), 2003, pp 3566-3572.
The Journal of Clinical Oncology is the semi-monthly peer-reviewed journal of the American Society of Clinical Oncology (ASCO), the world's leading professional society representing physicians who treat people with cancer.
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