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False-negative bone imaging due to etidronate disodium therapy
A Z Krasnow1, B D Collier, A T Isitman
1Department of Radiology, Medical College of Wisconsin, Milwaukee.
Clinical Nuclear Medicine
|April 1, 1988
Summary
Etidronate disodium (EHDP) interferes with bone imaging using Tc-99m methylene diphosphonate (Tc-99m MDP) by blocking tracer uptake. Patients may require a waiting period after discontinuing EHDP before accurate bone scans for metastases can be performed.
Area of Science:
- Nuclear Medicine
- Oncology
- Pharmacology
Background:
- Prostate cancer management often involves monitoring for bone metastases.
- Bone scintigraphy using Technetium-99m methylene diphosphonate (Tc-99m MDP) is a standard imaging technique.
- Etidronate disodium (EHDP) is a bisphosphonate used in managing conditions like bone metastases.
Observation:
- A patient undergoing prostate cancer evaluation for bone metastases showed altered Tc-99m MDP uptake during EHDP treatment.
- Minimal radiotracer uptake was observed in the bones, with significant retention in soft tissues.
- This altered distribution suggests a potential drug-tracer interaction.
Findings:
- The administration of EHDP significantly reduced the bony uptake of Tc-99m MDP.
- The structural similarity between EHDP and Tc-99m MDP likely leads to competitive binding at target sites.
- EHDP appears to saturate the binding sites crucial for Tc-99m MDP accumulation in bone.
Implications:
- Physicians must be aware of the potential for EHDP to interfere with bone scintigraphy.
- A prolonged washout period, potentially several months, may be necessary after EHDP discontinuation for effective bone imaging.
- This interaction necessitates careful patient management and timing of diagnostic procedures in oncology.