According to Dr. Judah Folkman, recent studies of childhood leukemia cases show that this cancer of the blood system does, unexpectedly, involve growth of new blood vessels into bone marrow.

Folkman, at Children's Hospital in Boston, studies angiogenesis - blood vessel growth. He said that in other types of cancer it was well known that new blood vessels must grow into solid tumors if they are to expand. But it was assumed that blood cancers such as leukemia would not require that, because leukemia involves unrestrained growth of malignant cells in the blood but no tumor formation.

"That idea was wrong," Folkman said here during a symposium on angiogenesis yesterday. Because a hormone that stimulates blood vessel growth was found in excessive amounts in urine of leukemia patients, "we began to take a new look at leukemia patients' bone marrow. It was a surprise to the pathologists" that tiny blood vessels were growing in bone marrow.