However, treatment regimens, particularly the newer generation of chemotherapy and radiation protocols, are generally successful at curing the disease. In spite of this, a recent study of European cancer registries showed significant geographic differences in the survival of blood-borne cancers, such as HD. 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 HD types in a region was a major factor in determining regional differences in HD 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 HD morphology, such as stage of disease at diagnosis and treatment, influenced outcome. The authors also confirmed the conclusions of previous studies that HD tumors with lymphocytic predominance had an excellent prognosis and HD tumors with lymphocytic depletion had significantly worse outcomes. Dr. Allemani and her colleagues conclude, 'differences in excess risk of death between the geographic regions diminished when corrected for morphology indicating that differences in morphologic case mix are an important determinant of regional survival differences for HD.'