Procedures used for determining the stage of breast cancer should be modified for pregnant women to avoid radiation exposure to the fetus. Nuclear scans cause fetal radiation exposure.[1] If such scans are essential for evaluation, hydration and Foley catheter drainage of the bladder can be used to prevent retention of radioactivity. Timing of the exposure to radiation relative to the gestational age of the fetus may be more critical than the actual dose of radiation delivered.[2] Radiation exposure during the first trimester (>0.1 Gy) may lead to congenital malformations, mental retardation, and increased relative risk of carcinogenesis. Doses greater than 1 Gy may produce congenital abnormalities. Doses of 0.1 Gy may result in fewer defects.

Chest x-rays with abdominal shielding are considered safe, but as with all radiologic procedures, they should be used only when essential for making treatment decisions.[1,3] A chest x-ray delivers 0.00008 Gy.[4]

For the diagnosis of bone metastases, a bone scan is preferable to a skeletal series because the bone scan delivers a smaller amount of radiation and is more sensitive. A bone scan delivers 0.001 Gy. Evaluation of the liver can be performed with ultrasound, and brain metastases can be diagnosed with a magnetic resonance imaging (MRI) scan. Data on magnetic resonance during pregnancy are not yet available, but gadolinium crosses the placenta and is associated with fetal abnormalities in rats.[5]

References

1. Gwyn K, Theriault R: Breast cancer during pregnancy. Oncology (Huntingt) 15 (1): 39-46; discussion 46, 49-51, 2001.  [PUBMED Abstract]
   
   
2. Barnavon Y, Wallack MK: Management of the pregnant patient with carcinoma of the breast. Surg Gynecol Obstet 171 (4): 347-52, 1990.  [PUBMED Abstract]
   
   
3. Nicklas AH, Baker ME: Imaging strategies in the pregnant cancer patient. Semin Oncol 27 (6): 623-32, 2000.  [PUBMED Abstract]
   
   
4. Gallenberg MM, Loprinzi CL: Breast cancer and pregnancy. Semin Oncol 16 (5): 369-76, 1989.  [PUBMED Abstract]
   
   
5. Yang WT, Dryden MJ, Gwyn K, et al.: Imaging of breast cancer diagnosed and treated with chemotherapy during pregnancy. Radiology 239 (1): 52-60, 2006.  [PUBMED Abstract]
   
   

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