Early neuro-otologic effects of three-dimensional irradiation in children with primary brain tumors.
OBJECTIVE
Central nervous system (CNS) irradiation can cause sensorineural hearing loss. The relationship between the dose to the cochlea and the development of hearing loss is unknown. Conformal radiation therapy (CRT) techniques facilitate accurate cochlear dosimetry. We modeled hearing threshold levels (HTL) after CRT in children with localized primary brain tumors (ependymoma, low- or high-grade astrocytoma, craniopharyngioma, or CNS germinoma) by using cochlear dose and clinical variables.


METHODS
We evaluated 72 children (median age, 9.5 years) with audiograms before and every 6 months after CRT (median follow-up, 16.6 months; range, 4.3-42.6 months). We used a mixed-effects model to predict change in hearing for each ear as a function of time, cochlear dose, and clinical variables.


RESULTS
Hearing was affected the greatest in patients with CSF shunts and pre-CRT ototoxic chemotherapy, enhanced by cochlear dose, and was more prominent on the right side. Hearing impairment after CRT alone occurred at low and intermediate frequencies in patients with shunts and supratentorial tumors when the cochlear dose exceeded 32 Gy. Patients with shunts and central supratentorial tumors developed intermediate-frequency hearing loss after CRT alone regardless of dose.


CONCLUSIONS
Hearing loss during the first 4 years after CRT alone is uncommon, although patients with shunts and supratentorial tumors appear to be at increased risk for low- and intermediate-frequency effects. CSF shunting and increased cochlear dose enhance the effect of ototoxic chemotherapy. If possible, the average cochlear dose should be <32 Gy over a 6-week course of treatment until more specific dose data become available.
Department ofRadiation Oncology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA. thomas.merchant@stjude.org
Thomas E
TE
Merchant
Ciara J
CJ
Gould
Xiaoping
X
Xiong
Nicole
N
Robbins
Junhong
J
Zhu
David L
DL
Pritchard
Raja
R
Khan
Richard L
RL
Heideman
Matthew J
MJ
Krasin
Larry E
LE
Kun
D000293:Adolescent; D000328:Adult; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000009:adverse effects; D001299:Audiometry; D001932:Brain Neoplasms / Q000188:drug therapy / Q000532:radiotherapy*; D002648:Child; D002675:Child, Preschool; D003051:Cochlea / Q000528:radiation effects*; D016371:Cranial Irradiation / Q000009:adverse effects*; D005260:Female; D005500:Follow-Up Studies; D034381:Hearing Loss / Q000209:etiology* / Q000473:pathology; D006319:Hearing Loss, Sensorineural / Q000209:etiology; D006801:Humans; D008297:Male; D011879:Radiotherapy Dosage; D020266:Radiotherapy, Conformal / Q000009:adverse effects*