First a patient hears the cancer diagnosis and then learns that the needed chemotherapy may cause temporary baldness. For many, the loss of hair is a huge cosmetic burden piled on the already terrible physical trauma of disease.

But help may be on the way, according to a study published Friday in the journal Science.Dr. A.A. Yunis, of the University of Miami Jackson Memorial Hospital Medical Center, said he and his colleagues have discovered "by chance" that an experimental cancer drug blocks hair loss in laboratory rats injected with some chemotherapy agents.

If the finding can be translated into drugs to treat humans, an expert said, "it would be of tremendous benefit" to cancer patients who now must endure the characteristic mark of chemotherapy baldness.

Yunis said his team made the discovery while testing cancer-fighting drugs on lab rats that had been injected with leukemia cells.

Half of the rats were treated with a drug called cytosine arabinoside, or ARA-C. The rest were treated with a combination of ARA-C and an experimental drug called ImuVert.

"We found, lo and behold, that the rats with ARA-C only became nude. They lost all their hair," said Yunis. "The ones with both ARA-C and ImuVert, however, did not lose hair at all."

Yunis said his group then tested ImuVert with another common cancer drug, doxorubicin, or DX. He said they found that rats with the DX-ImuVert combination also experienced no hair loss, while rats receiving only the DX lost hair on their heads and shoulders.

ImuVert combined with a third cancer drug, cyclophosphamide, however, did not prevent hair loss in the rats, said Yunis.

Dr. Ed Gelmann, chief of the department of medical oncology at Georgetown University in Washington, said that if a way can be found to prevent hair loss "patients will feel much better about chemotherapy."

Chemotherapy baldness is nearly always temporary. The hair usually grows back after the treatment cycle.