Radioiodine therapy during an unknown remained pregnancy and radiation exposure of the fetus. A case report.
OBJECTIVE
A papillary thyroid cancer staged as p T2N3M0 was treated in a 28-year-old woman by surgery, percutaneous radiation and radioiodine therapy (10 single applications ranging from 3300 to 3840 MBq with an average radioactivity of 3350 MBq). In the course of radioiodine therapy an attended gynaecologist found the woman pregnant in the 24th week of gravidity. Because the pregnancy remained unknown until this time radioiodine was administered during the 2nd and the 22nd week of pregnancy, each time 3700 MBq. Because of the risk of malformations this pregnancy was interrupted after consultation and taking the recommendations of the so-called Danish rule as a basis for the decision.


METHODS
Ovarian and fetal doses as well as the fetal thyroid exposure has been estimated as exactly as possible using data at hand. The fetus was studied with regard to possible consequences of radiation exposure by pathologico-anatomical, cytogenetic and radiobiological methods.


RESULTS
The accumulated ovarian doses resulting from the radioiodine administrations before pregnancy was estimated to 2200 mGy, the fetal doses resulting from the two administrations during pregnancy to 250 mGy in each case, and the fetal thyroid dose to between 90 Gy and 900 Gy for the 2nd therapy during pregnancy. In the fetus the most important changes were found within the thyroid gland (atrophy, sclerosis, subcapsular interstitial fibrosis, necrobiosis of follicular epithelial cells). On the other hand, analysing the karyotype using dermal fibroblastic cell cultures, no radiation induced chromosomal aberrations were seen.


CONCLUSIONS
Despite of all precautionary measures it seems to be conceivable that in extremely rare cases--in our 35-year experience with more than 20,000 radioiodine therapies only the present case--an early pregnancy may remain undetected. The results of these studies give useful information on effects to be expected as a result of radioiodine application during certain periods of pregnancy. They may help to extend the radiobiological knowledge with regard to the fetal period.
Arndt
D
D
Bundesgesundheitsamt, Dresden.
Mehnert
W H
WH
Franke
W G
WG
Woller
P
P
Laude
G
G
Rockel
A
A
Waller
M
M
D000032:Abortion, Therapeutic; D000328:Adult; D002291:Carcinoma, Papillary / Q000473:pathology / Q000532:radiotherapy*; D005260:Female; D005333:Fetus / Q000473:pathology / Q000528:radiation effects*; D006801:Humans; D007457:Iodine Radioisotopes / Q000009:adverse effects / Q000627:therapeutic use*; D008297:Male; D009367:Neoplasm Staging; D011182:Postoperative Care; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D011879:Radiotherapy Dosage; D011882:Radiotherapy, High-Energy / Q000009:adverse effects; D013964:Thyroid Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D014915:Whole-Body Counting
D007457:Iodine Radioisotopes