Antypas C, Sandilos P, Kouvaris J, Balafouta E, Karinou E, Kollaros N, Vlahos L
Department of Radiology, Medical School, University of Athens, Areteion Hospital, Greece.
Int J Radiat Oncol Biol Phys. 1998 Mar 1;40(4):995-9. doi: 10.1016/s0360-3016(97)00909-7.
The aim of the work was to estimate the radiation dose delivered to the fetus in a pregnant patient irradiated for breast cancer.
A 45-year woman was treated for left breast cancer using a 6 MV photon beam with two isocentric opposing tangential unwedged fields. Daily dose was 2.3 Gy at 95% isodose line given by two fields/day, 5 days/week. A total dose of 46 Gy was given in 20 fractions over a 4-week period. Pregnancy confirmed during the second therapeutic week. Treatment lasted between the second and sixth gestation week. Radiation dose to fetus was estimated from in vivo and phantom measurements using thermoluminescence dosimeters and an ionization chamber. In vivo measurements were performed by inserting either a catheter with TL dosimeters or ionization chamber into the patient's rectum. Phantom measurements were performed by simulating the treatment conditions on an anthropomorphic phantom.
TLD measurements (in vivo and phantom) revealed fetal dose to be 0.085% of the tumor dose, corresponding to a cumulative fetal dose of 3.9 cGy for the entire treatment of 46 Gy. Chamber measurements (in vivo and phantom) revealed a fetal dose less than the TLD result: 0.079 and 0.083% of the tumor dose corresponding to cumulative fetal dose of 3.6 cGy and 3.8 cGy for in vivo and phantom measurement, respectively.
It was concluded that the cumulative dose delivered to the unshielded fetus was 3.9 cGy for a 46 Gy total tumor dose. The estimated fetal dose is low compared to the total tumor dose given due to the early stage of pregnancy, the large distance between fundus-radiation field, and the fact that no wedges and/or lead blocks were used. No deterministic biological effects of radiation on the live-born embryo are expected. The lifetime risk for radiation-induced fatal cancer is higher than the normal incidence, but is considered as inconsequential.
本研究旨在估算接受乳腺癌放疗的孕妇胎儿所接受的辐射剂量。
一名45岁女性因左乳腺癌接受治疗，采用6兆伏光子束，两个等中心对置切线非楔形野。每日剂量为2.3戈瑞，在95%等剂量线处，每天由两个野给予，每周5天。在4周内分20次给予总剂量46戈瑞。在治疗的第二周确认怀孕。治疗持续于妊娠的第二至六周。使用热释光剂量计和电离室通过体内和体模测量来估算胎儿所接受的辐射剂量。体内测量通过将带有热释光剂量计的导管或电离室插入患者直肠进行。体模测量通过在人体模型上模拟治疗条件进行。
热释光剂量计测量（体内和体模）显示胎儿剂量为肿瘤剂量的0.085%，相当于整个46戈瑞治疗过程中胎儿累积剂量为3.9厘戈瑞。电离室测量（体内和体模）显示胎儿剂量低于热释光剂量计测量结果：分别为肿瘤剂量的0.079%和0.083%，对应体内和体模测量的胎儿累积剂量分别为3.6厘戈瑞和3.8厘戈瑞。
得出结论，对于46戈瑞的总肿瘤剂量，未受屏蔽的胎儿所接受的累积剂量为3.9厘戈瑞。由于妊娠早期、子宫底部与辐射野之间距离较大以及未使用楔形物和/或铅挡块这一事实，估算的胎儿剂量与所给予的总肿瘤剂量相比很低。预计辐射对活产胚胎不会产生确定性生物学效应。辐射诱发致命癌症的终生风险高于正常发病率，但被认为无关紧要。
