March 11 (HealthDay News) -- Between 1990 and 2004, five- and 10-year survival rates for non-Hodgkin lymphoma patients in the United States improved, a new study finds.

Researchers at the German Cancer Research Center in Heidelberg analyzed data from the Surveillance, Epidemiology and End Results (SEER) Program of the U.S. National Cancer Institute. Non-Hodgkin lymphoma, which affects about 20.4 out of every 100,000 people, includes several cancers of the immune system. In recent years, there have been advances in treatments for the disease.

"Overall, five-year relative survival increased from 50.4 percent to 66.8 percent, and 10-year survival increased from 39.4 percent to 56.32 percent between 1990 to 1992 and 2002 to 2004," the study authors wrote.

"Improvements were most pronounced in patients younger than 45 years [plus 26.8 and plus 27.1 percentage points for five- and 10-year survival, respectively], but improvements were seen in all age groups, in both sexes, in both nodal and extranodal disease, and in both low-grade and high-grade disease. Improvements in prognosis were less in black patients than in white patients, especially in younger black patients," the researchers said.

Two factors may explain these improved survival rates, according to the analysis.

"One is advances in therapy that have occurred between 1990 and 2004, particularly the introduction of antibody therapy for non-Hodgkin lymphoma," the researchers noted. "Treatment with antibody therapy and chemotherapy has extended life expectancy in many cases, but whether and how often this extension represents a true cure is still unknown."

The study authors also noted that improvements in the treatment of HIV have reduced the occurrence of HIV-related non-Hodgkin lymphomas and made them easier to treat.

"Our estimates of long-term survival in patients with non-Hodgkin lymphoma obtained by the period analysis for the 2002 to 2004 period are much higher than previously available survival estimates, which mostly pertain to patients diagnosed in the 1990s," the researchers concluded. "Timely disclosure of the improvements in survival achieved in patients, clinicians, researchers and the public is essential."

The study was published in the March 10 issue of the Archives of Internal Medicine.

SOURCE: JAMA/Archives journals, news release, March 10, 2008