National Survey of Japan for Myeloablative Total Body Irradiation Prior to Hematopoietic Stem Cell Transplantation

Abstract

In hematopoietic stem cell transplantation, survival rate of total body irradiation (TBI) containing myeloablative regimens tended to be superior, compared with other regimens without TBI. So TBI is increasingly being used, but the method varies among institutions. The last national survey of TBI in Japan was performed in 2002 and there are no recent data on TBI in Japan. In this time, the Japanese Radiation Oncology Study Group (JROSG) designed and performed the national survey of myeloablative TBI by questionnaire. The survey was performed in October 2015 and patients treated between January 2010 and December 2014 were reviewed. The questionnaire included questions regarding disease variation and TBI method. All 186 Japanese institutes in which TBI was done in 2015 in Japanese Radiation Oncology Database were approached. Ninety institutes (90/186; 48 %) replied and 82 institutes performed myeloablative TBI in this period. There were 2699 patients with malignant disease, the leukemia; 2082 patients (77 %), malignant lymphoma; 378 patients (14 %). There were 37 patients with nonmalignant disease, severe aplastic anemia; 20 patients (54 %), inborn errors of metabolism; 5 patients (14 %). Timing of TBI was after conditioning chemotherapy in 38 institutes (46 %), before conditioning chemotherapy in 19 institutes (23 %), not decided in 18 institutes (22 %). All institutes used linear accelerator. The radiation technique of long SSD was used in 72 institutes (87.8 %), moving couch in 7 institutes (8.5 %). The beam energy was 10MV in 54 institutes (66 %), 6 MV in 20 institutes (24 %). The most frequent total dose/fractions/days was 12 Gy/6 fr/3 days in 50 institutes (61 %), 12/4/4 in 11 institutes (13 %), 12/4/2 in 9 institutes (11 %), 10/4/2 in 3 institutes (4 %). The dose rate varied among the institutes, 10-26 cGy/min in 44 institutes (53.7 %), 5-9.88 cGy/min in 33 institutes (40.2 %) and 50-250 cGy/min in 5 institutes (6.1 %). Patient positions during TBI was supine position in 65 institutes (79.3 %), supine and prone position in 7 institutes (8.5 %). The beam arangement was Right-Left in 60 institutes (73.1 %), Anterior-Posterior in 13 institutes (15.9 %). Organs routinely shielded during TBI was lungs and lenses in 47 institutes (57.3 %), only lungs in 21 institutes (25.6 %), only lenses in 5 institutes (6.1 %) and no shielding in 8 institutes (9.8 %). In lung shielding institutes, the maximum acceptable total dose for lungs varied largely among the institutes and raged from 0 Gy to 12 Gy and most frequent dose was 8 Gy (19 institutes; 27.5 %). The results of the current survey indicate that TBI method varies strongly among institutes even in Japan. Because it is difficult to design multicenter randomized trials on TBI method, this survey results have been helpful to standardize the methods of TBI and conduct of multicenter clinical trials containing TBI.