The presence of
circulating tumor cells in bone marrow and peripheral blood of
cancer patients may reflect the aggressiveness of the disease. This also applies to
cancers that rarely give rise to overt bone marrow
metastases. The clinical validity of
micrometastasis detection for staging and prognostication depends on the sensitivity and reliability of the detection method. In
malignant melanoma, most studies have used
reverse transcriptase polymerase chain reaction (RT-PCR) techniques, commonly with
tyrosinase mRNA as the target molecule. Unfortunately, highly inconsistent results have been reported, raising doubts about this approach. In a study of 81
melanoma patients with metastatic disease, we used an immunobead rosetting method in which live
melanoma cells are selected and identified by binding of paramagnetic beads coated with the 9.2.27 antibody against the
high molecular weight melanoma-associated antigen. In bone marrow samples obtained from 60 patients, 14 (23.3%) were positive, compared to only two of 81 in blood. A highly significant correlation (p = 0.0001, log rank test) was found between
micrometastasis positivity and overall survival from time of removal of the primary
tumor. Moreover, in regression analysis it was found that the presence of micrometastatic cells was an independent and the most important
indicator of poor prognosis, with a relative risk of 5.38. The immunomagnetic method is simple, rapid, and highly sensitive and will be used in further prospective clinical studies.