Total body irradiation (TBI) in combination with chemotherapy, followed by bone marrow transplantation, has been shown to be beneficial in the treatment of hematological malignancies, some nonmalignant disorders of the hemopoietic system, and selected solid tumors. Presently, thousands of patients a year receive high-dose TBI, often before adulthood, followed by autologous or allogeneic bone marrow transplantation. This brings about increasing numbers of patients in long-term follow up after bone marrow transplantation. Knowledge regarding delayed effects of this treatment modality including high-dose TBI, therefore, has become more important.
One of the organs whose function is at risk after TBI is the testis. Many reports have described deleterious effects of irradiation and chemotherapy on the human testis. However, in addition to the establishment of infertility, testis size, and changes in hormone levels in these patients, the underlying causes within the testis cannot be studied in the human. In this respect, radiation experiments on nonhuman primates are relevant, because the response of the monkey to radiation does not seem to be significantly different from that of the human. This has been demonstrated for a number of acute effects, including those on the hemopoietic and intestinal system, and also for some late effects, such as tumor induction. Furthermore, spermatogenesis in both the human and the monkey has been shown to be rather radiosensitive. The induction of genetic damage, such as stable chromosomal aberrations, seems to be very low in the rhesus monkey, probably due to the extensive spermatogonial stem cell killing by the irradiation.