Second brain tumors following central nervous system radiotherapy in childhood

OBJECTIVE

The second tumour (ST) occurrence is a relatively uncommon late complication of radiotherapy but represents one of the most significant issues, especially in childhood oncology. We describe our experience with patients who developed second brain neoplasm following cranial irradiation in childhood.

METHODS

We identified nine patients who received radiotherapy owing to central nervous system tumour in childhood and subsequently developed the second brain tumour. The full clinical and radiological documentation and histopathological reports were reviewed. Risk factors such as age at irradiation, latency period to ST diagnosis, radiotherapy doses and volumes and other therapy methods were evaluated. We correlated the ST location with the three levels of irradiation dose (high, >40 Gy; medium, 25-40 Gy; and low <25 Gy).

RESULTS

Five meningiomas and four gliomas occurred as the ST after the mean time of 11.7 years after radiotherapy. The average age of children during irradiation was 4.6 years. The shorter latency time to the ST induction was found in children treated with chemotherapy (9 years vs 17.2 years). Seven STs developed in the area of high and moderate dose (>25 Gy), only two low-grade gliomas appeared in the low-dose region.

CONCLUSION

Our data suggest that the STs usually develop in the brain tissues that received doses >25 Gy in patients irradiated at a young age.

ADVANCES IN KNOWLEDGE

The low-dose volume seems not to be so significant for second brain neoplasm induction. Therefore, the modern intensity-modulated radiotherapy technique could be safely applied in paediatric patients.

Risk factors of recurrence in 157 MB/PNET patients treated in one institution

To evaluate the risk factors for recurrence of MB/PNET we analyzed the medical records of 157 patients treated at the Children's Memorial Health Institute between February 1981 and February 1997. The following factors were evaluated: age at diagnosis, gender, tumor size, tumor cells in the CSF, postoperative status, extent of resection and methods of treatment. We evaluated chemotherapy (CHT) doses, interval between courses, interval between surgery (S) and first course of CHT, interval between S and radiotherapy (RTX), and breaks during RTX. We divided patients into six groups: S alone, S+CHT, S+RTX, S+CHT+ RTX, S+RTX+CHT, S+CHT+RTX+ CHT. Age at diagnosis, gender, tumor size, extent of resection, postoperative status, intervals between courses of CHT, between S and the first course of CHT, and between S and RTX, and breaks during RTX had no statistical influence on relapse occurrence. Tumor cells in CSF were routinely checked for from January 1992 onward. In this group of 75 patients, 40 had tumor cells positive at surgery (28 relapsed), while in the group of 35 patients with negative tumor cells 14 relapsed (P=0.004). Out of 26 patients treated with S+RTX alone, 13 relapsed. Among 14 patients treated with S+RTX and prolonged CHT 6 relapsed. Out of 14 patients treated with S+CHT 13 relapsed; among 49 who received S+CHT+RTX 35 relapsed; and out of 51 patients treated with S+CHT+RTX+CHT 30 relapsed. In the multivariate analysis of treatment methods chemotherapy implemented after radiotherapy had a positive, though not statistically significant, influence on outcome (P=0.06). Among those receiving CHT the mean percentage of the ideal dose administered had a statistically significant influence on relapse: in the group of relapsed patients the mean dose was 76.1%, while in the group in continuous remission it was 83.7% (P=0.0013). On the basis of our data, we conclude that the presence of tumor cells in the CSF had a significant influence on the occurrence of relapse. Administration of appropriate doses of chemotherapy is extremely important for the occurrence of relapse and the final outcome of treatment. Prolonged adjuvant chemotherapy after radiotherapy seems to lower the risk of recurrence.