Blood test can detect sub-clinical metastasis in early stage melanoma patients

The test detects the presence of TA-90, a glycoprotein that can stimulate an immune response. In the early stages of disease, TA-90 is found in immune complexes in the blood, and these complexes can be detected using a sophisticated type of assay.

The study team, led by Dr. Mark C. Kelley, now based at Vanderbilt University Medical Center in Nashville, Tennessee, believe that ``TA-90 is the first tumor marker that accurately predicts subclinical metastatic disease and survival for patients with early-stage melanoma.'' Because the test can detect whether or not the cancer has spread, it provides physicians with better information about how to treat the disease.

``A significant proportion of patients thought to have localized, early-stage melanoma actually have subclinical metastasis,'' write the authors. ``Although surgical lymph node staging can detect regional lymph node metastasis, there is no way to detect (very early) disease accurately at other sites.''

High doses of interferon improve the survival chances of patients with high-risk melanoma, but the regimen is toxic, expensive, and only modestly successful. Identifying patients who have early-stage melanoma but in whom the disease has already spread would be extremely useful because these patients may greatly benefit from interferon therapy.

To test TA-90, researchers at John Wayne Cancer Institute at Saint John's Health Center in Santa Monica, California, identified 114 patients who underwent surgical removal of an early-stage melanoma tumor between January 1, 1980 and December 31, 1990. Some of these patients also had regional lymph nodes removed. Blood from each patient was collected before surgery and was analyzed for the presence of TA-90 immune complexes. If a removal, found to be microscopically positive for disease, or if a patient's melanoma subsequently recurred, subclinical metastasis (the symptomless spread of cancer) was considered to be present at the time of surgery.

The TA-90 test predicted subclinical metastasis in 43 of 56 patients, with 14 false-positive and 13 false-negative results, a significant improvement over other malignant tumor marker results. Five-year overall survival was 63% in the TA-90 positive group and 88% in the TA-90 negative group. Five-year disease free survival was also lower in the group of patients positive for the biomarker -- 46% compared with 82% in the TA-90 negative group.

Statistical analysis showed that TA-90 immune complex status is ``a strong, independent prognostic factor for both overall and disease-free survival'' in patients with early-stage melanoma, the researchers conclude. ``The TA-90 assay has the potential to improve dramatically the prognostic evaluation of (melanoma patients),'' study co-author, Dr. Donald L. Morton told Reuters Health.