The safety of lymphatic mapping in pregnant breast cancer patients using Tc-99m sulfur colloid.
This investigation was undertaken to assess the risk to the embryo/fetus associated with sentinel lymph node biopsy and lymphoscintigraphy of the breast performed in pregnant patients. Approximately 92.5 MBq (2.5 mCi) of filtered Tc-99m sulfur colloid was injected peritumorally the day before surgery in two nonpregnant women with breast cancer. The whole-body distribution of the radiopharmaceutical was evaluated using a gamma camera 1 hour after injection. We then calculated the absorbed dose to the embryo/fetus for three theoretical extreme scenarios of biodistribution and pharmacokinetics: 1) all of the injected radiopharmaceutical remains in the breast and is eliminated only by physical decay; 2) all of the injected radiopharmaceutical is instantaneously transported to the urinary bladder, where it remains and is eliminated only by physical decay; and 3) the injected radiopharmaceutical behaves as though it were administered intravenously, that is, it has the biodistribution and pharmacokinetics of Tc-99m sulfur colloid injected for a liver/spleen or bone marrow scan. The fetal radiation absorbed dose was then estimated for two Tc-99m dosages: 18.5 MBq (0.5 mCi) and 92.5 MBq (2.5 mCi). The Medical Internal Radiation Dosimetry (MIRD) program was used to estimate the absorbed doses to the embryo/fetus for the first two scenarios. Published data were used to calculate the doses for the third scenario. A single breast is not among the source organs in the MIRD program, so the heart was used as a surrogate in the first scenario. In the two breast cancer patients, whole-body gamma-camera images obtained 1 hour after radiopharmaceutical injection revealed no radioactivity except in the vicinity of the injection site. In the theoretical scenarios, with 92.5 MBq, the highest absorbed doses to the embryo/fetus were as follows: scenario 1, 7.74 x 10(-2) mGy at 9 months of pregnancy; scenario 2, 4.26 mGy during early pregnancy; and scenario 3, 0.342 mGy at 9 months of pregnancy. The maximum absorbed dose to the fetus of 4.3 mGy calculated for the worst-case scenario is well below the 50 mGy that is believed to be the threshold absorbed dose for adverse effects. Thus breast lymphoscintigraphy during pregnancy appears to present a very low risk to the embryo/fetus.
Keleher
Angela
A
Department of Surgical Oncology, Box 444, University of Texas M.D.Anderson Cancer Center, Houston, Texas 77030, USA. hkuerer@mail.mdanderson.org
Wendt
Richard
R
Delpassand
Ebrahim
E
Stachowiak
Anne Marie
AM
Kuerer
Henry M
HM
D001943:Breast Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism; D005260:Female; D005333:Fetus / Q000378:metabolism*; D006801:Humans; D008198:Lymph Nodes / Q000000981:diagnostic imaging / Q000378:metabolism; D008207:Lymphatic Metastasis / Q000000981:diagnostic imaging; D011247:Pregnancy; D011252:Pregnancy Complications, Neoplastic / Q000000981:diagnostic imaging* / Q000378:metabolism; D011829:Radiation Dosage; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics*; D013671:Technetium Tc 99m Sulfur Colloid / Q000493:pharmacokinetics*
D019275:Radiopharmaceuticals; D013671:Technetium Tc 99m Sulfur Colloid