Regional differences in the survival of Hodgkin's Lymphoma (disease) can be partially explained by the type of Hodgkin's, according to a new population level study. The July 15, 2006 issue of CANCER, journal of the American Cancer Society, the study reveals that while nodular sclerosis Hodgkin's was much more common in the United States than Europe, there was significant Hodgkin's variability across Europe. Furthermore, Hodgkin's type (or morphology) accounted for differences between the U.S. and most of Europe, except Eastern Europe. The study also supported data that lymphocyte predominance Hodgkin's had the best prognosis and Hodgkin's with lymphocytic depletion had the worst.
Hodgkin's Lymphoma is a cancer of the lymphatic system, which includes lymph nodes and the spleen. Like many cancers, Hodgkin's comes in multiple types based on cellular characteristics. Studies have shown that certain morphologies have worse prognoses. However,
treatment regimens, particularly the newer generation of chemotherapy protocols, are generally successful in causing lasting remission (disease free).
In spite of this, a recent study of European cancer registries showed significant geographic differences in the survival of blood-borne cancers, such as Hodgkin's. In order to understand the causes of these regional differences, Claudia Allemani, Ph.D. of the Istituto Nazionale per lo Studio e la Cura dei Tumori in Milan, Italy and the EUROCARE Working Group compared 6,726 cases from 37 cancer registries in Europe (EUROCARE-UK, EUROCARE-west, and EUROCARE-east) and 3,442 cases from 9 U.S. (SEER) registries diagnosed between 1990 and 1994 and followed at least for five years.
Analysis showed that the distribution of Hodgkin's types in a region was a major factor in determining regional differences in five-year survival and risk of death. Using the relative excess risk (RER) of death to compare mortality risk, the investigators found that there was no significant RER difference between EUROCARE-west and the U.S. SEER databases when adjusting for gender and age, with or without morphology. However, morphology did account for the differences in mortality risk between cases in the EUROCARE-UK and EUROCARE-east regions. When morphology was adjusted for, mortality risk remained significantly increased in EUROCARE-east, suggesting factors other than Hodgkin's type/morphology, such as stage of disease at diagnosis and treatment, influenced outcome.
The authors also confirmed the conclusions of previous studies that Hodgkin's tumors with lymphocytic predominance had an excellent prognosis and Hodgkin's tumors with lymphocytic depletion had significantly worse outcomes.
Dr. Allemani
