Arthritis & Rheumatism, Volume 60,
October 2009 Abstract Supplement
The 2009 ACR/ARHP Annual Scientific Meeting
Philadelphia October 16-21, 2009.
Renal Dosimetry for Patients Treated with Total Body Irradiation (TBI) for Severe Systemic Sclerosis (SSc) On the SCOT (Scleroderma: Cyclophosphamide or Transplantation) Trial
Craciunescu, O., Steffey, B., Kelsey, C., Prosnitz, R., Larrier, N., Paarz-Largay, C., Sullivan, KM
To describe techniques and dosimetry in delivering TBI to patients with severe SSc enrolled on a multicenter stem cell transplant (SCT) protocol.
The SCOT protocol employs an immunoablative regimen of high-dose CY, ATG and 800 cGy TBI given in 200 cGy fractions twice a day followed by CD34 selected autologous SCT. Due to possible organ impairment from SSc, shielding is used to limit irradiation to kidney and lung to a total of 200 cGy. Since renal shielding has not been previously used during TBI, block thickness and dosimetry were investigated and guidelines developed for safety and technique. Due to concern for worsening of SSc nephropathy, CT-based planning was performed without IV contrast. Data on kidney shape and the shifts from prone to standing position were assessed using diagnostic ultrasound (US). During treatment, we performed in vivo dosimetry for each patient using OneDose® (Sicel Technologies) at eleven locations, including the umbilicus, mid mediastinum, lumbar spine, hip, and under the lung/kidney block and calculated the mean dose at each location. Minimum distances between the kidney blocks (dkB) and the dose to the lumbar spine were also determined.
Phantom measurements revealed that a 1020% dose inhomogeneity in the lumbar spine region could be achieved with a minimum kidney block separation of 45 cm (typical width of a vertebral body). Eleven subjects have been treated on the transplant arm of the trial at Duke since 2006. The average lumbar spine dose was 179.6 ± 18.1 cGy, with an average dkB of 5.0 ± 1.0 cm. Block design and placement were accomplished using a combination of CT and US or CT alone. Kidney-localization based on the combination of CT and US yielded more accurate block positioning and reduced superior-inferior block margins. Kidney shape proved similar among the eleven patients imaged, leading to a potential use of standard kidney blocks. The US information revealed a wide range of kidney displacement, both inferior and superior. The mean inferior displacement of the left kidney was 1.2 ± 1.1 cm, and 1.0 ± 1.3 cm for the right kidney. One subject exhibited a superior displacement of 3.5 cm for the right kidney. The average dose measured for the prescription point was 193.4 ± 5.1 cGy, for the mid mediastinum area 196.6 ± 10.6 cGy, for the hip area 206 ± 11.8 cGy, for under the lung blocks 54.7 ± 7.7 cGy, and under the kidney blocks, 50.8 ± 7.1 cGy. With this technique, no deterioration in renal function was observed and the study continues to enroll patients.
Prescribed TBI can be delivered with acceptable homogeneity over the entire body. Attenuation of TBI dosing to the kidneys by 75% can be achieved while maintaining a 1020% dose inhomogeneity. Localization of the kidneys is more accurate using both CT and US as compared to CT alone.
Supported by NIH award AI-05419.
To cite this abstract, please use the following information:
Craciunescu, O., Steffey, B., Kelsey, C., Prosnitz, R., Larrier, N., Paarz-Largay, C., et al; Renal Dosimetry for Patients Treated with Total Body Irradiation (TBI) for Severe Systemic Sclerosis (SSc) On the SCOT (Scleroderma: Cyclophosphamide or Transplantation) Trial [abstract]. Arthritis Rheum 2009;60 Suppl 10 :1713