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EXPECTED BIODISTRIBUTION OF BEXXAR
Authored By: Xiaoni Hong and Akash Sharma.
Patient: 61 year old male
History: 60-year-old male with relapsed large cell lymphoma.
Image Size:[small][as-submitted]

Fig. 1
On Day 0, most of the tracer is in the blood pool and the activity in normal hepatic and splenic parenchyma is less than that in the cardiac blood pool.

Fig. 2
Day 2, the activity in the blood pool decreases significantly and there is decreased accumulation of activity in normal hepatic and splenic parenchyma. There is no retention of the tracer in the urinary tract to suggest obstruction, and there is no diffuse lung activity greater than that of blood pool at any time.

Fig. 3
Day Cp6, the activity in the blood pool decreases significantly and there is decreased accumulation of activity in normal hepatic and splenic parenchyma. There is no retention of the tracer in the urinary tract to suggest obstruction, and there is no diffuse lung activity greater than that of blood pool at any time.

Fig. 4
Comparison Day0, 2 and 6 images Expected biodistribution of BEXXAR.

Fig. 5
MIR's Bexxar protocol
Image Size:[small][as-submitted]

Findings:

Whole-body images were obtained on Day 0 (prior to voiding and 34 minutes after the completion of the infusion of I-131 BEXXAR), Day 2, and Day 6. In addition, images of an I-131 standard, as well as background counts, were obtained on each of these days. Counts from these images were used to estimate the whole-body retention time. The whole-body retention time was measured to be 107 hours (acceptable values are between 50 and 150 hours).

The biodistribution of I-131 BEXXAR also was assessed. On Day 0, most of the tracer is in the blood pool and the activity in normal hepatic and splenic parenchyma is less than that in the cardiac blood pool. On Day 2 and 6, the activity in the blood pool decreases significantly and there is decreased accumulation of activity in normal hepatic and splenic parenchyma. There is no retention of the tracer in the urinary tract to suggest obstruction, and there is no diffuse lung activity greater than that of blood pool at any time.

OPINION:

1. Whole-body retention time is 107 hours.

2. Expected biodistribution of BEXXAR.

Diagnosis: Expected biodistribution of BEXXAR.
General Discussion: Long history: 60-year-old male with relapsed large cell lymphoma. This study was requested to measure the whole-body retention time and to determine the biodistribution of BEXXAR before therapeutic administration of the radiopharmaceutical.

Radiopharmaceutical: 5.2 mCi I-131 tositumomab (BEXXAR) i.v.

Discussion: I-131 BEXXAR (Iodine I-131 tositumomab) is a radiolabeled murine IgG2a lambda monoclonal antibody directed against the CD20 antigen, which is found on the surface of normal and malignant B lymphocytes. It is used for treatment of relapsed or refractory low-grade follicular or transformed non-Hodgkin’s lymphoma. Prior to treatment, whole-body imaging is acquired on 3 separate days (Days 0, 2-4 and 6-7) following injection with I-131 BEXXAR. Background and standard counts are also obtained. From these data, the whole-body retention time can be calculated. The therapeutic dose is determined using the whole-body retention time. In addition, the biodistribution of BEXXAR is assessed. An altered biodistribution of BEXXAR is a contraindication to treatment with BEXXAR.

Acceptable Biodistribution: On the first imaging timepoint: Most of the activity is in the blood pool (heart and major blood vessels) and the uptake in normal liver and spleen is less than that in the heart.
On the second and third imaging timepoints: The activity in the blood pool decreases significantly and there is decreased accumulation of activity in normal liver and spleen. Images may show uptake by thyroid, kidney, and urinary bladder and minimal uptake in the lungs. Tumor uptake in soft tissues and in normal organs is seen as areas of increased intensity.

Altered Biodistribution: On the first imaging timepoint: If the blood pool is not visualized or if there is diffuse, intense tracer uptake in the liver and/or spleen or uptake suggestive of urinary obstruction the biodistribution is altered. Diffuse lung uptake greater than that of blood pool on the first day represents altered biodistribution.
On the second and third imaging timepoints: Uptake suggestive of urinary obstruction and diffuse lung uptake greater than that of the blood pool represent altered biodistribution.
Total-body residence times of less than 50 hours and more than 150 hours represent altered biodistribution.





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Case Number: 118421Owner(s): Xiaoni Hong and Akash SharmaLast Updated: 02-07-2013
Anatomy: Other   Pathology: Other
Modality: Nuc MedAccess Level: Readable by all users, writable by NucMed Certifiers
Keywords: nmACR: 90000.83430, 90000.83430

Case has been viewed 29 times.
Certified by Akash Sharma on 03-10-2010

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