Renal shielding and dosimetry for patients with severe systemic sclerosis receiving immunoablation with total body irradiation in the scleroderma: cyclophosphamide or transplantation trial.
OBJECTIVE
To describe renal shielding techniques and dosimetry in delivering total body irradiation (TBI) to patients with severe systemic sclerosis (SSc) enrolled in a hematopoietic stem cell transplant protocol.


METHODS
The Scleroderma: Cyclophosphamide or Transplantation (SCOT) protocol uses a lymphoablative preparative regimen including 800 cGy TBI delivered in two 200-cGy fractions twice a day before CD34(+) selected autologous hematopoietic stem cell transplantation. Lung and kidney doses are limited to 200 cGy to protect organs damaged by SSc. Kidney block proximity to the spinal cord was investigated, and guidelines were developed for acceptable lumbar area TBI dosing. Information about kidney size and the organ shifts from supine to standing positions were recorded using diagnostic ultrasound (US). Minimum distance between the kidney blocks (dkB) and the lumbar spine region dose was recorded, and in vivo dosimetry was performed at several locations to determine the radiation doses delivered.


RESULTS
Eleven patients were treated at our center with an anteroposterior (AP)/posteroanterior (PA) TBI technique. A 10% to 20% dose inhomogeneity in the lumbar spine region was achieved with a minimum kidney block separation of 4 to 5 cm. The average lumbar spine dose was 179.6 ± 18.1 cGy, with an average dkB of 5.0 ± 1.0 cm. Kidney block shield design was accomplished using a combination of US and noncontrast computerized tomography (CT) or CT imaging alone. The renal US revealed a wide range of kidney displacement from upright to supine positions. Overall, the average in vivo dose for the kidney prescription point was 193.4 ± 5.1 cGy.


CONCLUSIONS
The dose to the kidneys can be attenuated while maintaining a 10% to 20% dose inhomogeneity in the lumbar spine area. Kidneys were localized more accurately using both US and CT imaging. With this technique, renal function has been preserved, and the study continues to enroll patients.
Craciunescu
Oana I
OI
Department of Radiation Oncology, Duke University Medical Center, Durham, NC 27710, USA. oana.craciunescu@duke.edu
Steffey
Beverly A
BA
Kelsey
Chris R
CR
Larrier
Nicole A
NA
Paarz-Largay
Cathy J
CJ
Prosnitz
Robert G
RG
Chao
Nelson
N
Chute
John
J
Gasparetto
Cristina
C
Horwitz
Mitchell
M
Long
Gwynn
G
Rizzieri
David
D
Sullivan
Keith M
KM
D003520:Cyclophosphamide / Q000627:therapeutic use; D004867:Equipment Design; D018380:Hematopoietic Stem Cell Transplantation; D006801:Humans; D007166:Immunosuppressive Agents / Q000627:therapeutic use; D007668:Kidney / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000528:radiation effects*; D008159:Lumbar Vertebrae / Q000528:radiation effects; D008168:Lung / Q000528:radiation effects; D009929:Organ Size; D056888:Patient Positioning; D011832:Radiation Injuries / Q000517:prevention & control*; D011835:Radiation Protection / Q000379:methods*; D011859:Radiography; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D012595:Scleroderma, Systemic / Q000532:radiotherapy*; D016683:Supine Position; D019172:Transplantation Conditioning / Q000379:methods; D014463:Ultrasonography; D014916:Whole-Body Irradiation / Q000379:methods*
D007166:Immunosuppressive Agents; D003520:Cyclophosphamide
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