전이성 분화갑상선암을 치료할 목적으로 사용된 $^{131}I$에 의한 염색체 손상여부를 검정하기 위하여 치료 전후의 자매염색분체교환(SCE)의 빈도 및 말초혈액의 백혈구수를 정상대조군과 환자군에서 조사하였다. 1) 정상인으로 설정한 대조군에 있어서의 자매염색분체교환 빈도수가 $3.8{pm}0.4$인데 비하여 $^{131}I$ 투여전의 SCE 빈도가 $4.2{pm}0.7$으로 차이를 보이지 않았다(p=0.17). 2) $^{131}I$ 투여후 2일째 SCE 빈도는 $7.9{pm}0.8$으로 치료전에 비해 유의하게 증가하였으며 (p<0.001), 9일째에는 $6.4{pm}0.6$으로 2일째에 비해서는 유의하게 감소하였으나(p=0.002), 치료전에 비해서는 아직도 유의하게 높았다 (P<0.001). 3) 같은 기간동안 백혈구의 수는 유의한 변화를 보이지 않았다. 결과적으로, $^{131}I$ 치료후 염색분체의 손상은 일어나며, 서서히 회복되나 1주일 이내에는 완전한 회복을 보이지 않음을 알 수 있었다.
To evaluate the genotoxic effect of $^{131}I$, lymphocytes from 9 patients who underwent large dose (150 mCi) $^{131}I$ therapy after total thyroidectomy were studied for sister chromatid exchanges (SCE) before and after their first radioiodine treatments. Frequency of SCE (FSCE) was counted in chromosomes of 30 lymphocytes in each patients, and was expressed as numbers of SCE per cell. Numbers of leukocytes were also observed during $^{131}I$ therapy. Pretreatment FSCE ($4.2{pm}0.7$) was not different from the control ($3.8{pm}0.4$, p=0.17). However, the frequency was significantly elevated after $^{131}I$ administration (at the second day, $7.9{pm}0.8$, p<0.001) and was diminished but still significantly elevated after a week (at 9th day, $6.4{pm}0.6$, p<0.001). While counts of leukocytes in the peripheral blood showed no change (p> 0.05). In conclusion, chromatids of human lymphocytes were significantly damaged after $^{131}I$ treatment without any bone marrow supression. And the repair of SCE was not complete within one week.
