Improvements in the radiotherapy of medulloblastoma, 1946-1975.

The prognosis in medulloblastoma has often been reported to be gloomy, and five-year survival rates of approximately 25% are often reported. In recent years, however, some centers have published results that indicate a possible cure rate of 60% or even more. During the years 1946-1975, 50 children received radiotherapy for medulloblastoma at the University Hospital, Lund, Sweden. During this period the target volume had been defined in three different ways, whereas the target-absorbed dose had not differed. When only the demonstrated tumor was treated, the ten-year survival rate was 5%. If the spinal subdural space also was included, it rose to 25%, and when the whole subdural space was treated in addition to the demonstrated tumor, the projected ten-year survival rate was 53%. It is apparent that the target volume in the radiotherapy of medulloblastoma should include not only the demonstrated tumor but also the whole subdural space from the tip of the frontal lobes down to and including the second sacral segment. The size of the target-absorbed dose to be aimed at is not settled, but should consider not only the cure rate but also the performance status of the survivors. It seems from the present series that an absorbed dose of 45 Gy in not more than 30 fractions over six weeks to the demonstrated tumor and 30 Gy in 20 fractions over four weeks to the subdural space resulted in a fair frequency of tumor healing and minimal side effects. The delivery of this complicated treatment demands a high degree of precision in the technique. In this material the performance status of the children was not affected by the radiation treatment.