Thyroid dysfunction as a late effect in childhood medulloblastoma: a comparison of hyperfractionated versus conventionally fractionated craniospinal radiotherapy.
OBJECTIVE
Primary hypothyroidism is a common sequela of craniospinal radiotherapy in the treatment of childhood medulloblastoma. Due to the strong radiobiologic rationale, hyperfractionation can reduce the delayed effects of radiation injury.


METHODS
The authors compared the incidence of thyroid dysfunction after conventionally fractionated radiotherapy (Group A, n = 20 patients) vs. hyperfractionated radiotherapy (Group B, n = 12 patients) in a group of pediatric patients with posterior fossa primitive neuroectodermal tumor (PNET).


RESULTS
The mean age at the time of tumor diagnosis was 7.4 years in Group A and 8.4 years in Group B. Thyroid function was evaluated yearly, with ultrasonographic examination every 2 years. The patients were followed after diagnosis for a mean of 10.8 years for Group A and 6.0 years for Group B. Approximately 80% of the Group A (16/20) and 33.3% of the Group B (4/12) patients developed primary hypothyroidism within a similar period after irradiation (4.2 vs. 3.5 years, respectively). Analysis by cumulative incidence function demonstrated a significant difference in the risk of developing thyroid dysfunction between these two groups of patients (p < 0.05). Ultrasonography showed reduced thyroid volume in 7 Group A patients and structural changes in 21 patients (17 Group A, 4 Group B cases); a thyroid benign nodule was detected in 2 Group A patients.


CONCLUSIONS
The current study findings suggest that the use of hyperfractionated craniospinal radiotherapy in the treatment of childhood medulloblastoma is associated with a lower risk of these patients' developing late thyroid dysfunction.
Ricardi
U
U
Department of Radiation Oncology, Regina Margherita Children's Hospital, Turin, Italy. umberto.ricardi@esanet.it
Corrias
A
A
Einaudi
S
S
Genitori
L
L
Sandri
A
A
di Montezemolo
L C
LC
Besenzon
L
L
Madon
E
E
Urgesi
A
A
D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use; D017024:Chemotherapy, Adjuvant; D002648:Child; D002675:Child, Preschool; D003131:Combined Modality Therapy; D003388:Cranial Fossa, Posterior; D016371:Cranial Irradiation / Q000009:adverse effects*; D019583:Dose Fractionation, Radiation; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007037:Hypothyroidism / Q000000981:diagnostic imaging / Q000453:epidemiology / Q000209:etiology*; D015994:Incidence; D015192:Infratentorial Neoplasms / Q000188:drug therapy / Q000532:radiotherapy* / Q000601:surgery; D007558:Italy / Q000453:epidemiology; D015993:Life Tables; D008130:Lomustine / Q000008:administration & dosage; D008297:Male; D008527:Medulloblastoma / Q000188:drug therapy / Q000532:radiotherapy* / Q000601:surgery; D011832:Radiation Injuries / Q000000981:diagnostic imaging / Q000453:epidemiology / Q000209:etiology*; D018714:Radiotherapy, Adjuvant; D011882:Radiotherapy, High-Energy / Q000009:adverse effects*; D012074:Remission Induction; D012189:Retrospective Studies; D012306:Risk; D013961:Thyroid Gland / Q000000981:diagnostic imaging / Q000528:radiation effects*; D016606:Thyroid Nodule / Q000000981:diagnostic imaging / Q000453:epidemiology / Q000209:etiology; D013997:Time Factors; D016896:Treatment Outcome; D014463:Ultrasonography; D014750:Vincristine / Q000008:administration & dosage
D014750:Vincristine; D008130:Lomustine