Initiation of spermatogenesis during chemotherapy for leukemia

How does chemotherapy treatment damage the prepubertal testis?

Chemotherapy treatment is a mainstay of anticancer regimens, significantly contributing to the recent increase in childhood cancer survival rates. Conventional cancer therapy targets not only malignant but also healthy cells resulting in side effects including infertility. For prepubertal boys, there are currently no fertility preservation strategies in use, although several potential methods are under investigation. Most of the current knowledge in relation to prepubertal gonadotoxicity has been deduced from adult studies; however, the prepubertal testis is relatively quiescent in comparison to the adult. This review provides an overview of research to date in humans and animals describing chemotherapy-induced prepubertal gonadotoxicity, focusing on direct gonadal damage. Testicular damage is dependent upon the agent, dosage, administration schedule and age/pubertal status at time of treatment. The chemotherapy agents investigated so far target the germ cell population activating apoptotic pathways and may also impair Sertoli cell function. Due to use of combined chemotherapy agents for patients, the impact of individual drugs is hard to define, however, use of in vivo and in vitro animal models can overcome this problem. Furthering our understanding of how chemotherapy agents target the prepubertal testis will provide clarity to patients on the gonadotoxicity of different drugs and aid in the development of cytoprotective agents.

Review : Infertility after chemotherapy: A review of the risks and strategies for prevention

Purpose. Infertility as a late complication of cancer chemotherapy, focusing on specific drug-related ef fects, effects observed in the treatment of certain malignancies, and strategies for prevention is re viewed.

Data Sources. A MEDLINE search of articles from 1966 to present was conducted using the terms infertility, antineoplastics, amenorrhea, azospermia, oogenesis, and spermatogenesis. Additional refer ences were identified using review articles and phar macology textbooks.

Study Selection. All human studies reported in English language were included. Animal studies were included when human data were insufficient or un available.

Data Synthesis. Data on the infertility effects of individual antineoplastic agents are difficult to inter pret for several reasons, including small sample sizes, lack of prechemotherapy fertility assessment, inade quate long-term follow-up, and use of regimens in cluding multiple agents. In general, the incidence and severity of antifertility effects are dependent on the total dosage delivered, duration of therapy, and age at exposure. The alkylating agents have the most signif icant effects on fertility. Fertility outcomes have been reported for several different malignancies, especially in patients cured of Hodgkin's disease and testicular cancer. Information on specific antineoplastic agents and cancers are reviewed. Several methods have been employed to decrease gonadotoxic effects, but none have been effective.

Conclusions. Infertility is a common late com plication of cancer chemotherapy that is receiving increasing attention as the number of cancer survi vors increases. Health care professionals should be aware of infertility risks associated with antineoplastic agents and certain malignancies, and patients should be informed of these risks as treatment decisions are made.

Male gonadal toxicity

Cancer treatment with chemotherapy or radiotherapy causes gonadal toxicity in male patients. The endpoint of most concern for future reproductive options is the induction of prolonged azoospermia, which may or may not be reversible. The immediate effects of therapy and its reversibility are most readily observed in post-pubertal patients, but the same antineoplastic regimens given to prepubertal males can induce permanent azoospermia. The probability of permanent azoospermia is related to the specific agents used and their doses. The most damaging are alkylating agents (particularly chlorambucil, procarbazine, cyclophosphamide, melphalan, and busulfan), cisplatin and radiation to the region of the testicles.

Reproduction following treatment for childhood leukemia: a population-based prospective cohort study of fertility and offspring

Of all children diagnosed with leukemia in Denmark, Finland, Iceland, Norway, and Sweden, 981 had discontinued therapy before 1985 and had been followed up annually after cessation of therapy. Progeny was registered and fertility evaluated among survivors who passed age 18 years without a relapse (n = 299). By April 1989, 48 offspring were registered, one of whom had congenital anomalies. This was no more than expected from the incidence of birth defects in the general population. No childhood malignancies or genetic diseases have so far been diagnosed in the progeny. In the study group, none of the 19 female and 8 male survivors of myeloid leukemias had become parents, and only 4 fathers were reported among the 131 male survivors of acute lymphoblastic leukemia (ALL). However, 23 of the 149 females treated for ALL had delivered 41 children. Fertility was measured as cumulative rates of first birth by maternal age. In a Cox regression analysis, cases who had received prophylactic radiation of the central nervous system (CNS) had a lower first birth rate than those without radiation (rate ratio 0.39, 95% CI 0.15-1.00), indicating that doses of 18-24 Gy to the brain may possibly be a risk factor. By using the Norwegian birth cohort of 1966 as a control group, matching the median year of birth for the study subjects, the group of female ALL survivors as a whole was as likely as the general female population to have given birth up to the age of 23. The first generation of females successfully treated for childhood ALL seems to have a nearly normal reproductive pattern during young adulthood, without increased risk of congenital anomalies in the offspring. However, cranial radiation as CNS prophylaxis may possibly impair subsequent reproduction.

Effects of chemotherapy on fertility

Over recent years radical improvements in the treatment of malignant disease have resulted in the cure of patients in or approaching reproductive age, and with that cure, the effects on gonadal function have become apparent. Gonadal failure is particularly important in Hodgkin's disease, germ cell tumours, choriocarcinoma, and leukaemia, diseases of young people which are largely curable. Premature ovarian and testicular failure are easily missed by doctors concerned primarily with the erradication or arrest of a life-threatening disease, but for the patient the hormonal, psychological and social sequelae of treatment may be devastating. In this article we review the effects of chemotherapy on gonadal function and discuss the management of gonadal failure.

Normal or early development of puberty despite gonadal damage in children treated for acute lymphoblastic leukemia

To determine the timing of pubertal development and the frequency of gonadal dysfunction in children who survive acute lymphoblastic leukemia, we assessed pubertal status and the plasma levels of sex steroids, gonadotropin, and inhibin in 45 children (20 girls and 25 boys) who had received combination chemotherapy along with 24 Gy of irradiation to the cranium (modified LSA2L2 protocol). We also reexamined testicular biopsy specimens, obtained at the time of the cessation of chemotherapy, for the presence of germ cells. Germ-cell damage, indicated by marked elevations in the plasma level of follicle-stimulating hormone (P less than 0.001 for the comparison with normal children), was evident in both sexes and was confirmed in the boys by the absence of germ cells in the testicular biopsy specimens and by the small size of the testes for pubic-hair stage. Only 44 percent of the pubertal girls had measurable plasma inhibin levels, as compared with more than 93 percent of normal pubertal girls. Although plasma sex-steroid levels were normal, the secretion of luteinizing hormone in response to stimulation with gonadotropin-releasing hormone was elevated in the pubertal children (P less than 0.01 for the comparison with normal controls)--a finding that suggests compensation for decreased gonadal function. Despite clear evidence of gonadal damage, girls had early menarche at a mean age (+/- SD) of 11.95 +/- 0.91 years, as compared with the Australian standard of 12.98 +/- 1.11 years (P less than 0.01). Thus, in girls, puberty was early despite primary gonadal damage. Thirteen of 23 boys reached puberty at a mean age of 12.36 +/- 0.73 years. We conclude that treatment for acute lymphoblastic leukemia may lead to primary gonadal damage in both sexes, regardless of the age at treatment, but that the secondary characteristics of puberty develop at a normal age or, in girls, relatively early.