Antibodies pinpoint migrating mini-tumors.

Approximately one in three breast cancer patients will eventually die from the disease even though her oncologist found no identifiable signs of distant malignant spread at the time of surgery. That grim statistic has driven researchers to seek out ever more sensitive techniques for detecting tiny "satellite" cancers, or micrometastases, spawned by the initial tumor.

Scientists at the Memorial Sloan-Kettering Cancer Center in New York City now report dramatic progress on the road to such tests. Their trials indicate that a trio of monoclonal antibodies may provide an "exquisitely sensitive" diagnostic tool, says Michael P. Osborne, who led the studies. When incubated with cells extracted from bone marrow, the antibodies could highlight even a single cancer cell among 1 million normal cells, he says. That's 100 times more sensitive than the most discriminating diagnostic technique available today, which relies solely on cultured bone marrow cells (SN: 6/2/90, p.341).

In the May 15 CANCER RESEARCH, Osborne and his co-workers report indirectly identifying breast cancer micrometastases among marrow cells that had been incubated with the monoclonal antibodies. The antibodies bind only to cells derived from epithelial tissue, allowing them to be stained a telltale red. Because bone marrow normally contains no epithelially derived cells, Osborne explains, oncologists interpret such cells as metastases from an epithelially derived breast tumor.

At last week's meeting of the American Society of Clinical Oncology in Houston, Osborne described using an earlier, fluorescent version of the same antibody cocktail, which highlighted breast cancer micrometastases in marrow samples from 31 percent of the 152 patients studied. A two-year follow-up of these women, he says, indicates that the presence of micrometastases -- especially those involving 10 or more cells -- may identify patients who face the greatest risk of early cancer recurrence, signaling the need for aggressive postsurgical chemotherapy.