A comparison of chromosomal aberrations induced by in vivo radiotherapy in human sperm and lymphocytes

Chromosomal aberrations in human sperm and lymphocytes were compared before and after in vivo radiation treatment of 13 cancer patients. The times of analyses after radiotherapy (RT) were 1, 3, 12, 24, 36, 48 and 60 months. The median total radiation dose was 30 Gy and the testicular dose varied from 0.4 to 5.0 Gy. Human sperm chromosome complements were analysed after fusion with golden hamster eggs. There were no abnormalities in sperm or lymphocytes before RT. Following RT there was an increase in the frequency of numerical and structural chromosomal abnormalities in both lymphocytes and sperm. For structural abnormalities there were more rejoined lesions (dicentrics, rings) in lymphocytes and more unrejoined lesions (chromosome breaks, fragments) in sperm. After RT there was a dramatic increase in the frequency of chromosomal abnormalities in lymphocytes: at 1 mo. the frequency was 42%, at 3 mo. 25%, at 12 mo. 14%, at 24 mo. 11%, at 36 mo. 9%, at 48 mo. 7% and at 6 mo. 4%. Since the majority of men were azoospermic after RT, there is little data on sperm chromosome complements before the analyses performed at 24 mo. post-RT. At 24 mo. the frequency of abnormalities was 13%, followed by 21% at 36 mo., 12% at 48 mo. and 22% at 60 mo. Thus it appears that the frequency of lymphocyte chromosomal abnormalities had an initial marked increase after RT followed by a gradual decrease with time whereas the frequency of sperm chromosomal abnormalities was elevated when sperm production recovered and remained elevated from 24 to 60 mo. post-RT. This difference in the effect of time makes it very difficult to compare abnormality rates in lymphocytes and sperm and to use analysis of induced damage in somatic cells as surrogates for germ cells since the ratio between sperm and lymphocytes varied from 1:1 (at 24 mo. post-RT) to 5:1 (at 60 mo. post-RT).