Thymus-dependent regeneration of CD4+ T lymphocytes occurs primarily in children, whereas even young adults have deficiencies in this pathway. Our results suggest that rapid T-cell regeneration requires residual thymic function in patients receiving high-dose chemotherapy.

Chemotherapy appears to be an effective primary postoperative treatment for many malignant brain tumors in young children. Disease control for one or two years in a large minority of patients permitted a delay in the delivery of radiation and, on the basis of preliminary results, a reduction in neurotoxicity. For patients who had undergone total surgical resection or who had a complete response to chemotherapy, the results are sufficiently encouraging to suggest that radiation therapy may not be needed in this subgroup of children after at least one year of chemotherapy.

The overall risk of second malignancies after Ewing's sarcomas is similar to that associated with treatment for other childhood cancers. The radiation dose-dependency of secondary sarcomas justifies modification in therapy to reduce radiation doses.

One hundred seventy-seven children and young adults with various malignant neoplasms were prospectively tested for hearing loss after they had received cisplatin (n = 146), cranial irradiation (n = 18), or both (n = 13). Adequate renal function, no history of treatment with ototoxic drugs other than cisplatin, and availability for repeated audiometric testing were requirements for enrollment. Substantial hearing loss, defined as a hearing threshold of 50 dB or greater, was noted in only 11% of the cohort on tests conducted at the common speech frequencies (500 to 3,000 Hz). About half the patients had substantial deficits at higher frequencies (4,000 to 8,000 Hz). The probability of substantial hearing loss was directly related to the cumulative dose of cisplatin. In nonirradiated patients tested at the speech frequencies, there was a negligible risk of substantial deficits over the dose range of 90 to 360 mg/m2. As the dose increased to 720 mg/m2, the risk increased to 22%. In irradiated patients who later received cisplatin, cumulative drug doses as low as 270 mg/m2 were associated with a high probability of substantial hearing loss, suggesting potentiation of ototoxicity when these therapies are used together. Hearing acuity was either not affected or only minimally decreased in the irradiation-only group. Younger age, prior irradiation, and the presence of a CNS tumor each contributed significantly to the severity of hearing deficits at given cisplatin dose levels. We conclude that early increases in hearing threshold at a stimulus frequency of 4,000 Hz indicate probable subsequent deficits at lower frequencies, especially in young children with CNS tumors who have received cranial irradiation. The probability charts derived from this analysis should provide a useful tool for predicting hearing loss in the speech frequencies.

ICRF-187 reduces the risk of developing short-term subclinical cardiotoxicity in pediatric sarcoma patients who receive up to 410 mg/m2 of doxorubicin. Response rates to chemotherapy, event-free and overall survival, and noncardiac toxicities appear to be unaffected by the use of ICRF-187. Additional clinical trials with larger numbers of patients are needed to determine if the short-term cardioprotection afforded by ICRF-187 will reduce the incidence of late cardiac complications in long-term survivors of childhood cancer.