The effects of irradiation and chemotherapy on growth

Long-term effects of radiation therapy on cognitive and endocrine function in children with leukemia and brain tumors

BACKGROUND

As the number of long-term survivors of childhood cancer has grown, it has become increasingly clear that central nervous system therapy may have serious long-term effects on cognition and endocrine function. These complications have been studied most extensively in children with brain tumors and leukemia.

REVIEW SUMMARY

Children with acute lymphoblastic leukemia previously treated with cranial irradiation are at risk for cognitive decline. Chemotherapy-only regimens, which rely on high-dose frequently administered methotrexate, are also associated with producing cognitive dysfunction. Children irradiated for brain tumors are even more vulnerable. Risk factors include perioperative morbidity, young age, large-volume high-dose cranial irradiation, supra-tentorial location of tumor, moyamoya syndrome, and leukoencephalopathy. Cognitive decline is progressive over at least a decade. The most common radiation-induced endocrinopathies are hypothyroidism and growth hormone deficiency. Treatment effects on growth are multifactorial and include growth hormone deficiency,spinal shortening, precocious puberty, undetected hypothyroidism,and poor nutrition. Fifty percent to 80% of children treated with craniospinal radiation for brain tumors will experience growth failure. In hopes of reducing neurotoxicity, current treatments limit the dose and volume of radiation while adding chemotherapy. Results have not been uniformly positive, however, and may increase toxicity in some cases.

CONCLUSIONS

The standard of care in 2004 is that children who have been treated for brain tumors and leukemia should be monitored for cognitive and endocrine dysfunction. Until effective non-neurotoxic treatment is identified, long-term effects assessments are essential to maximize the quality of life of survivors of childhood cancer.

Endocrine outcome in children with medulloblastoma treated with 18 Gy of craniospinal radiation therapy

Craniospinal radiation therapy (CSRT) combined with chemotherapy results in significant endocrine morbidity. Between 1987 and 1990, a trial using 18 Gy was conducted to treat 10 young children with medulloblastoma. There were 7 survivors. We compared the endocrine outcome in these children (group 18 Gy) to that of a comparable group treated with conventional doses of CSRT that ranged from 23 to 39 Gy (group CD). Both groups had an identical history of chemotherapy and tumor stage and were treated with recombinant growth hormone therapy (rhGH). The mean age of group 18 Gy at diagnosis was 4.0 years, and rhGH treatment was initiated in 6 children at age 9.2 years. Group CD (12 children) was diagnosed at a mean age of 5.8 years and rhGH started in 11 children at a mean age of 9.6 years. The dose of rhGH used in both groups was identical (0.3 mg/kg/wk). For group 18 Gy, adult heights and sitting heights (a mean standard deviation score of -1.01 +/- 1.11 and -1.62 +/- 1.16, respectively) were statistically greater (P < 0.05) than those for group CD (mean standard deviation score of -2.04 +/- 0.83 and -3.16 +/- 1.43, respectively). Moreover, adult heights of group 18 Gy were not different from midparental heights, unlike group CD, whose adult heights were less than midparental heights (P < 0.0001). Of other endocrine sequelae, 10 patients of the CD group were hypothyroid, 3 had adrenal insufficiency, 3 had hypogonadism, and 2 had early puberty. In contrast, within group 18 Gy, only 1 was hypothyroid (P = 0.006) and 1 had early puberty. We conclude that endocrine morbidity was significantly reduced with 18 Gy CSRT in young children with medulloblastoma.