MONDAY, Dec. 11 (HealthDay News) -- A combination of three chemotherapy drugs -- pentostatin, cyclophosphamide and rituximab -- produced significant clinical response in patients with previously untreated chronic lymphocytic leukemia, according to a study presented Sunday at the American Society of Hematology annual meeting.

Each year, about 10,000 people in the United States are diagnosed with this blood and bone marrow cancer.

"Chronic lymphocytic leukemia is incurable but continues to be made more manageable with the advent of powerful new chemoimmunotherapy tools," lead researcher Dr. Neil E. Kay, a Mayo Clinic hematologist, said in a prepared statement.

"We and our collaborators at Ohio State University... have done previous research on pentostatin that led us to believe there would be success with this (three-drug) regimen, and are pleased with the results," Kay said.

The 64 patients in the study received six cycles of the combined regimen. The patients also received a year of treatment with the anti-infection drug sulfamethoxazole-trimethoprim and the antiviral drug acyclovir.

At the start of the study, the researchers determined that most of the patients had significant disease progression and/or a high expectation of rapid advancement of their disease.

Following treatment, 91 percent of the patients in the study experienced improvement in their condition, including 41 percent who achieved complete response.

"We are very pleased with the results of this study. This is a new, viable option for high-risk patients who might not have had much hope before, and it's especially exciting that it works for patients of all age groups," Kay said.

More information

The U.S. National Cancer Institute has more about chronic lymphocytic leukemia.