Neuroblastoma after prenatal exposure to phenytoin: cause and effect?

Neuroblastoma and Fetal Exposure to Phenytoin in a Child Without Dysmorphic Features

Despite the fact that the teratogenic effects of phenytoin have been suggested in several case reports, the evidence for a possible oncogenic potential of phenytoin has not been widely recognized. Recently, neuroblastoma as well as other neuroectodermal and non-ectodermal tumors has been seen in several children exposed to phenytoin prenatally. Previous cases have been almost uniformly associated with the features of “fetal hydantoin syndrome” and none have been developmentally normal. We report a developmentally-normal boy of 2½ years with an abdominal neuroblastoma whose mother had been on phenytoin (as well as carbamazepine) throughout gestation. We review the various neoplasms which have been reported in the offspring of mothers receiving phenytoin.

Neuroteratogens in man: An overview with special emphasis on the teratogenicity of antiepileptic drugs in pregnancy

The most active growth and development of the human cerebrum and cerebellum occurs in the second half of pregnancy and in the first year of life. It is therefore not surprising that many teratogens may also affect development causing slight, moderate or even severe brain damage. The "classical" antiepileptic drugs (AEDs) valproic acid (VPA), phenytoin, phenobarbital, primidone and carbamazepine are all considered to be teratogenic. They may increase the rate of major congenital anomalies including neural tube defects (NTD), cause specific facial and other dysmorphic features--the "Anti Epileptic Drug Syndrome" (AEDS) and often some degree of mental impairment. Of these AEDs, the most teratogenic seems to be valproic acid, causing about 2% of NTD and an additional increase of 4-8% in major congenital anomalies. Phenytoin also increases the rate of various anomalies, but apparently not of NTD. Phenobarbital primidone and carbamazepine are also teratogenic and impair intellectual function but to a lesser extent than VPA and phenytoin. Cognition is mainly impaired in the children that also exhibit the AEDS. The impairment is slight to moderate, leaving the affected children with a close to borderline intelligence. Lamotrigine monotherapy in pregnancy seems to be relatively safe. In general, polytherapy is more dangerous to the fetus than monotherapy and, at least for VPA and lamotrigine, there seems to be a "threshold effect".

Drug-induced congenital defects: strategies to reduce the incidence

Approximately 1% of congenital anomalies relate to pharmacological exposure and are. in theory, preventable. Prevention consists of controlled administration of drugs known to have teratogenic properties (e.g. retinoids, thalidomide). When possible, prevention could take the form of the use of alternative pharmacological therapies during the pre-conception period for certain specific pathologies, selecting the most appropriate agent for use during pregnancy [e.g. haloperidol or a tricyclic antidepressant instead of lithium; anticonvulsant drug monotherapy in place of multitherapy; propylthiouracil instead of thiamazole (methimazole)], and substitution with the most suitable therapy during pregnancy (e.g. insulin in place of oral antidiabetics; heparin in place of oral anticoagulants; alpha-methyldopa instead of ACE inhibitors). Another strategy is the administration of drugs during pregnancy taking into account the pharmacological effects in relation to the gestation period (e.g. avoidance of chemotherapy during the first trimester, avoidance of nonsteroidal anti-inflammatory drugs in the third trimester, and avoidance of high doses of benzodiazepines in the period imminent to prepartum).

Lymphoblastic lymphoma following prenatal exposure to phenytoin

PURPOSE

Oncogenesis has been associated with prenatal exposure to phenytoin, concomitant with or independent of the fetal hydantoin syndrome. The majority of reported cases have been embryonal tumors of neural crest origin and have occurred in the first 3 years of life.

PATIENTS AND METHODS

We report a boy who was exposed to phenytoin throughout gestation and later developed T-lymphocyte lymphoblastic lymphoma, a previously unreported malignancy associated with in utero phenytoin exposure. Previously reported cases of neoplasia occurring after such exposure are tabulated.

CONCLUSION

The actual transplacental oncogenic potential of phenytoin and the epidemiology of this association are poorly understood. Phenytoin-induced alterations in lymphocyte-mediated immunosurveillance or oxidative metabolic clearance may be etiologic. Inquiry into prenatal phenytoin exposure should be done in any child who develops cancer, especially those who develop a rare tumor or present with a more common tumor at an unusually young age. Continued documentation of such cases will advance the understanding of phenytoin-associated transplacental oncogenesis.

Hormonal treatment in pregnancy: a possible risk factor for neuroblastoma

In the last 4 years, 24 cases of neuroblastoma were treated in the Pediatric Hematology-Oncology Unit at the Chaim Sheba Medical Center, 8 of whom were under 1 year of age. Four of them were the product of a pregnancy-induced or preserved by gonadotropins, clomiphene citrate, or progestational hormones. These drugs are known to produce a higher than normal level of estradiol or progesterone in the early stages of pregnancy. Our observation led to the hypothesis that high levels of progestational hormones given during pregnancy are a risk factor for neuroblastoma in infancy.

Teratogenicity and carcinogenicity in a twin exposed in utero to cyclophosphamide

A 29-year-old pregnant woman diagnosed with acute lymphocytic leukemia maintained remission with daily cyclophosphamide and intermittent prednisone treatment. She delivered a male twin with multiple congenital abnormalities who was diagnosed with papillary thyroid cancer at 11 years of age and stage III neuroblastoma at 14 years of age. The female twin was unaffected and has exhibited normal development to date. First trimester exposure to cyclophosphamide has been associated with major malformations. Metabolites of cyclophosphamide have been demonstrated to be teratogens and carcinogens in animals. Differences in placental or fetal hepatic cytochrome P-450 may account for the variability in response between the twins. In addition, disparity between the twins may be the result of differences in metabolite inactivating enzymes present either in fetal liver or placenta. The risk of second malignancies caused by alkylating agents such as cyclophosphamide has been well documented in adults and children but to the best of our knowledge this is the first description of transplacental second cancer.

International variations in the incidence of neuroblastoma

The International Agency for Research on Cancer has coordinated a worldwide study of childhood cancer incidence, with data from over 50 countries. We present here the results for neuroblastoma. In predominantly white Caucasian populations the age-standardized rate was 7-12 per million, and 6-10% of all childhood cancers were neuroblastomas. Rates were highest in the first year of life (25-50 per million, 30% of total neuroblastoma incidence), and decreased with age to 15-20 per million (50% of the total) at age 1-4, 2-4 per million (15%) at 5-9 and 1-1.5 per million (5%) at 10-14. In the United States, black children had an incidence of 8.5 per million compared with 11.5 among Whites; Blacks tended to be older than Whites at diagnosis. The highest rate in Africa was in Bulawayo, Zimbabwe (8.0 per million) and the lowest in West Nile, Uganda, with no cases registered. Incidence in Israel was similar to that in many white populations, with Jews having a particularly high rate. In other parts of West Asia neuroblastoma had a low relative frequency, suggesting that incidence is low. Rates were also low throughout much of southern and eastern Asia, including India and China. Incidence in Japan was somewhat higher, though less than in Western countries, with the deficit most pronounced in the first year of life; these data relate to the period before mass screening of infants for neuroblastoma in the regions concerned. Incidence was generally higher in regions and among ethnic groups enjoying a higher standard of living, though previous studies within single countries had suggested that neuroblastoma is more common among less affluent groups. Blacks in Africa and the United States may have a weaker genetic predisposition to neuroblastoma, but some of the deficit in many developing countries is likely to be due to under-diagnosis.

Cancer in children of epileptic mothers and the possible relation to maternal anticonvulsant therapy

Cancer incidence among 3,727 offspring of women hospitalised for epilepsy in Denmark between 1933 and 1962 was evaluated in a record-linkage survey with the national cancer registry. The children were identified from hospital charts, population listings, and parish registries. For all children (born before and after their mothers' hospitalisation), no excess of cancer was found in comparison with the general population (49 observed vs 53.8 expected). Among the 2,579 children born after their mothers' first admission for epilepsy, and thus presumably exposed in utero to anticonvulsant drugs, 14 cancers were identified compared to 13.8 expected (relative risk 1.0; 95% confidence interval 0.6-1.7). Contrary to some previous reports, cancers of the brain and nervous system were not significantly increased (3 observed vs 2.2 expected). These data provide no evidence that anticonvulsant drugs are transplacental carcinogens, and indicate that overall increases in risk as high as 80% are unlikely.