The risk of stillbirth or neonatal death among the offspring of women who had survived childhood cancer and had received radiation therapy (radiotherapy) when they were children, is higher compared to other women, says a report published in the peer-reviewed medical journal The Lancer.
Thanks to medical advances, a significant number of children and teenagers who had cancer years ago are now surviving into adulthood and wishing to start families. Dr John Boice, and Dr Lisa B Signorello, both of the International Epidemiology Institute, Rockville, MD, USA, and Vanderbilt University, Nashville, TN, USA, and team set out to find out whether exposure to radiation used for cancer therapy early in life affects the risk of stillbirth or dying very soon after birth for these people’s offspring.
Although not proven, radiation-induced damage of human germ cells might be passed on to the offspring of patients, which could have adverse effects on reproduction and the health of the baby. This damage could also affect individuals who are exposed to radiation and chemicals in occupational or other settings, such as nuclear power stations.
The researchers gathered data from the Childhood Cancer Survivor Study (CCSS), covering 25 US institutions and 1 in Canada, and calculated the risk of stillbirth and neonatal death among the offspring of men and women who had survived childhood cancer. All the CCSS patients were under 21 years of age when diagnosed with cancer and had subsequently survived for at least five years.
Among the 1,148 men and 1,657 women who had survived childhood cancer, there were 4,946 pregnancies:
- Irradiation of the testes (men), pituitary gland (women), and use of alkylating chemotherapy drugs (both sexes) were not linked to a raised risk of stillbirth or early baby death.
- Uterine and ovarian irradiation radically increased (by 9 times) the risk of stillbirth and neonatal death across all age groups combined, when doses greater than 10•00 Gy were used.
- For females treated before puberty, irradiation of the uterus and ovaries at doses as low as 1•00-2•49 Gy increased the risk of stillbirth or neonatal death by almost 5 times
- When doses over 2.5 Gy were used, the risk was increased 12 times.
The authors wrote:
High-dose pelvic irradiation can permanently impair growth and blood flow to the uterus and results in a reduced uterine volume, and these effects of radiation are likely to be dependent on age. Whether these types of effects on the uterus increase the risk of placental or umbilical-cord anomalies or other factors already linked to stillbirth, or whether they operate through different mechanisms needs clarification.
The researchers also found that even if males who underwent radiation exposure had suffered permanent transmissible damage, it would be difficult to detect in all but the largest and most heavily exposed populations because paternal influences on the risk of stillbirth are outweighed by maternal and external (e.g. prenatal care) factors.
They wrote:
No effect was noted in this cohort of men exposed to testicular irradiation at levels far higher than would be expected from background exposure, diagnostic medical, or occupational settings.
(conclusion) For men exposed to gonadal irradiation, there does not seem to be an increased risk of stillbirth or neonatal death among their offspring, which is reassuring not only for male survivors of childhood cancer but also for men exposed to ionising radiation in occupational or other settings. For women, however, high-dose uterine or ovarian radiation does seem to have important adverse effects, which are most likely to be attributable to uterine damage. Therefore, careful management is warranted for pregnant women treated with high-doses of pelvic irradiation before they have reached puberty.
Dr Lisa B Signorello ScD, Prof John J Mulvihill MD, Daniel M Green MD, Heather M Munro MS, Prof Marilyn Stovall PhD, Rita E Weathers BS, Prof Ann C Mertens PhD, John A Whitton MS, Leslie L Robison PhD, Prof John D Boice ScD
The Lancet, Early Online Publication, 23 July 2010
doi:10.1016/S0140-6736(10)60752-0
Written by Christian Nordqvist