Bone metastases

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Bone metastases

• Lindsay Bryant

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Nuclear Medicine

• Radiopharmaceutical administered to the patient
  and subsequently recording its distribution in
  the body over a defined period of time.
• Used to detect pathology
• Very sensitive
• Nonspecific

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Radiopharmaceuticals

• No physiologic response when administered for
  diagnostic or therapeutic purposes. Selective
  uptake of these compounds by various organs forms
  the basis for nuclear imaging
• Two components
• main component - distributed
• radionuclide tagged to this component
• Emits gamma rays which permit detection of the
  compound
• Components localize by active transport,
  phagocytosis, etc.
• Physiologic function can be assessed, but
  spatial resolution is relatively poor

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Common Nuclear Procedures

1. Cardiac studies
2. Skeletal studies
3. Renograms and renal scans
4. Ventilation-Perfusion studies
5. PET studies
6. Evaluation of neurodegenerative disorders, brain
   tumor recurrence, and myocardial viability.

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Less Common Nuclear Procedures

1. Diagnostic thyroid studies
2. Hepatobiliary studies
3. Brain imaging
4. White blood cell studies
5. Gastrointestinal bleeding studies
6. Lymphoscintigraphy
7. Parathyroid scans

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99mTc bone scintigraphy

• Effective method for screening the whole body for
  bone metastases
• 99mTc methylene diphosphonate (MDP) is the most
  frequently used isotope.
• 99mTc planar bone scintiscans help identify
  tumors by detecting the increased osteoblastic
  activity.

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Scintigraphy Indications

• Staging in asymptomatic patients
• Evaluation of persistent pain (with negative
  radiograph findings)
• Determining the extent of bone metastases ( with
  positive radiograph findings)
• Differentiating metastatic from traumatic
  fractures

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Indications continued

• Routinely done as part of initial staging of LUNG
  and BREAST cancer
• The risk of presenting with metastatic brain or
  bone disease is sufficiently high
• Not routinely done as part of initial staging of
  COLON cancer
• The risk is relatively low for metastases to bone
  or brain and bone scans are not done unless
  symptoms or other findings indicate a potential
  problem.

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Scintigraphy

• The classic pattern appears as the presence of
  multiple randomly distributed focal lesions
  throughout the skeleton

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Bone Metastases
A 99mTc-MDP bone scan in the anterior and
posterior projections demonstrates multiple foci
of increased radiopharmaceutical accumulation
(spine, ribs, pelvis, and left clavicle) with
the typical appearance of bone metastases
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Advantages

• Low cost
• Widely available
• Useful in imaging entire skeleton
• Sensitive
• 90 for FDG-PET (18- fluorodeoxyglucose )
• 82 for whole-body MRI
• 71 for 99mTc bone scintiscanning
• Continues to be used as initial screening
  investigation

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Disadvantages

• Findings are nonspecific in determining the
  cause of increased uptake, particularly in
  solitary lesions.
• Poor spatial and contrast resolution.
• Further imaging is required to characterize
  regions of disseminated abnormality.
• CT or MRI is required to localize an area of
  increased glucose metabolism

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False Positives of of 99mTc bone scintiscans

• Sensitivities are reportedly 62-89.
• Many benign processes and normal variants can
  produce an area of increased isotope uptake that
  mimics a metastatic deposit.
• Solitary areas of abnormal uptake benign
  processes occur in approximately one third of
  patients with malignant disease.

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Differential Diagnosis of multiple scintigraphic
abnormalities

• Metabolic problems (eg, Cushing syndrome)
• Osteomalacia
• Trauma
• Arthritis
• Osteomyelitis
• Paget disease
• Infarctions

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False Negatives of 99mTc bone scintiscans

• Some metastases may produce normal scintiscan
  findings.
• Cold or photopenic metastases may be found in
  association with lesions of highly aggressive
  anaplastic carcinomas

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SUMMARY

• Nuclear Imaging has an important role in the
  detection, diagnosis, prognostication, treatment
  planning, and follow-up monitoring of bone
  metastases. Further imaging or imaging-guided
  techniques may be required to confirm the
  diagnosis, to establish the extent of the
  disease, and to find the primary tumor.

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References

• Thomas, MB, Hoff, PM, Wolffe, RA.
  Gastrointestinal Carcinomas in The MD Anderson
  Manual of Medical Oncology. McGraw-Hill
  Companies. 2006
• Wilfred, CG. Bone Metastases. www.emedicine.com