Keleher Angela, Wendt Richard, Delpassand Ebrahim, Stachowiak Anne Marie, Kuerer Henry M
Department of Surgical Oncology, Box 444, University of Texas M.D.Anderson Cancer Center, Houston, Texas 77030, USA.
Breast J. 2004 Nov-Dec;10(6):492-5. doi: 10.1111/j.1075-122X.2004.21503.x.
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.
本研究旨在评估孕妇进行前哨淋巴结活检及乳腺淋巴闪烁成像对胚胎/胎儿的风险。在两名非妊娠乳腺癌女性患者手术前一天，在肿瘤周围注射约92.5 MBq（2.5 mCi）经滤过的锝-99m硫胶体。注射后1小时，使用γ相机评估放射性药物的全身分布情况。然后，我们针对生物分布和药代动力学的三种理论极端情况计算了胚胎/胎儿的吸收剂量：1）所有注射的放射性药物都留在乳腺中，仅通过物理衰变消除；2）所有注射的放射性药物瞬间转运至膀胱，并留在膀胱中，仅通过物理衰变消除；3）注射的放射性药物的行为就如同静脉注射一样，即具有用于肝脏/脾脏或骨髓扫描而注射的锝-99m硫胶体的生物分布和药代动力学。接着针对两种锝-99m剂量（18.5 MBq（0.5 mCi）和92.5 MBq（2.5 mCi））估算胎儿辐射吸收剂量。使用医学内照射剂量学（MIRD）程序估算前两种情况下胚胎/胎儿的吸收剂量。利用已发表的数据计算第三种情况的剂量。在MIRD程序中，单个乳腺并非源器官，因此在第一种情况下将心脏用作替代器官。在这两名乳腺癌患者中，放射性药物注射后1小时获得的全身γ相机图像显示，除注射部位附近外无放射性。在理论情况下，对于92.5 MBq，胚胎/胎儿的最高吸收剂量如下：情况1，妊娠9个月时为7.74×10⁻² mGy；情况2，妊娠早期为4.26 mGy；情况3，妊娠9个月时为0.342 mGy。在最坏情况下计算出的胎儿最大吸收剂量4.3 mGy远低于被认为是产生不良影响的阈值吸收剂量50 mGy。因此，孕期乳腺淋巴闪烁成像对胚胎/胎儿的风险似乎非常低。
