Radiation treatment for medulloblastoma. A 21-year review.

One hundred and twenty-two patients with medulloblastoma received postoperative irradiation at the Princess Margaret Hospital, Toronto, from 1958 to 1978, inclusive. The surgical procedure in these patients was total resection (44 patients), subtotal resection (66 patients), or biopsy alone (12 patients). Twenty-five patients received adjuvant chemotherapy. Overall 5- and 10-year survival rates were 56% and 43%, respectively. Improved survival rates were associated with an increased degree of resection and with posterior fossa radiation doses of 5200 rads or more. The posterior fossa was the common site of first relapse (in 56 patients, 46%). Systemic metastases at first relapse occurred in 18 of 52 patients (35%), and were associated with the use of ventriculosystemic shunts. Millipore filters did not prevent systemic relapse in shunted patients. A subset of 15 patients who received a posterior fossa dose of 5200 rads or more after a total resection had a 5-year survival rate of 77%, which remained constant to 10 years. This result is considered to be the upper limit that can be achieved by current treatment methods.