Regional differences exist in allogeneic stem cell transplantation rates for acute leukemia

Allogeneic stem-cell transplantation (allo-SCT) is a curative treatment for advanced hematologic malignancies, although it is frequently accompanied by severe complications and the practice is usually limited to experienced medical teams [1]. Regional differences in indications and management strategies for allo-SCT among physicians and institutions have been indicated; however, their existence and factors associated with them among physicians and institutions remain unknown. We examined the differences in allo-SCT rates for acute leukemia among prefectures and districts in Japan, and investigated the association between the differences and several possible factors. Japan’s prefectures comprise the 47 administrative units of the country, and districts make up ten areas divided according to geographical and historical backgrounds: Hokkaido, Tohoku, Koshinetsu, Kanto, Tokai, Hokuriku, Kinki, Chugoku, Shikoku, and Kyushu. Since 97% of the patients who underwent allo-SCT for acute leukemia from 2000 to 2004 were younger than 60 years in Japan [2], we assumed that allo-SCT was indicated in patients aged less than 60. We defined alloSCT rates as the rate of the number of patients who underwent allo-SCT to that of patients with acute leukemia. We investigated the number of patients with acute leukemia aged less than 60 as a denominator and the number of those who underwent allo-SCT under the age of 60 as a numerator. We estimated the annual number of new patients with acute leukemia under the age of 60 in each prefecture and district, using the incidences of acute leukemia by age-groups in Japan [3] and the population by age-groups in each prefecture according to a census in 2004 [4]. We defined the number of treated patients in each district as the estimated number of patients with acute leukemia, while the number of patients in each prefecture was adjusted by patient migration to and from other prefectures [5]. The number of patients who underwent alloSCT for acute leukemia under the age of 60 in each prefecture and district from 2000 to 2004 was obtained from the annual report in 2005 published by the Japan Society for Hematopoietic Cell Transplantation (JSHCT) [2]. We assumed the percentage of acute leukemia to the primary diseases for which allo-SCT was indicated in each prefecture to be the same as the national average (83%) during the same time period [2], because JSHCT reports the total numbers of the primary diseases for which allo-SCT was indicated in Japan without the breakdown of data by prefecture. We investigated the association between the differences and several possible factors using the Spearman correlation coefficient (significance level 0.05). They included physicians per unit population [6], the numbers of