The adult presentation of medulloblastoma is an infrequent disease entity that shows both similarities and discrepancies with its pediatric counterpart. Adult medulloblastoma differs mainly in the incidence of more laterally located tumors and more desmoplastic histologic findings compared with pediatric tumors. In the current study, a lateral location was observed in 53% and desmoplastic histologic features in 40% of the patients. In previous adult medulloblastoma series, the incidence of a lateral location was reported to be 29–71% and that of desmoplastic histologic features 25–50%. Park reported an incidence of 7% lateral tumors and 18% desmoplastic variant in 144 children with medulloblastoma.

The 5-year survival rate in this study compares favorably with both pediatric and adult medulloblastoma series. In well-documented retrospective adult medulloblastoma series reporting results of 13–147 patients, the 5-year overall survival rate ranged between 40% and 84% and the disease-free survival rate between 32% and 63%. In the current study, the disease-free survival rate was 63% at 5 years, but had decreased to 50% by 8 years. One-half of the recurrences were after 2 years, contrary to pediatric patients whose tumors recur mostly in the first 2 years.

Spinal seeding at presentation, although not very common, is one of the most important prognostic factors for recurrence. In the current study, only 3 patients had evidence of spinal metastases at diagnosis, and all had recurrence despite adequate postoperative treatment. This result is consistent with other adult medulloblastoma series.

The RT dose to the posterior fossa appeared to be a significant prognostic factor for posterior fossa control in the current study, similar to other studies in both pediatric and adult populations. A radiation dose of 54 Gy is suggested as the threshold dose for postoperative effectiveness. Higher radiation doses ≤72 Gy, fractionated, twice daily have not revealed superior control.

Usually, the aim is to keep the interval between surgery and RT as short as possible, taking into account operative scar tissue healing in all postoperative oncologic situations. The studies investigating this factor have not been able to show a detrimental effect of a delay in treatment results for medulloblastoma. In a study from the University of Florida, prolongation of the overall RT treatment time adversely affected the treatment results, but the interval between surgery and the start of RT had no effect on the treatment results for the pediatric medulloblastoma patients. In the study by Jenkin from Saudi Arabia in which 16% of 173 patients were >14 years old, no significant differences in outcome were found when the variables of the time from the first resection to the first day of RT (<25 vs. ≥25 days) and the duration of any interruption of RT in excess of 7 days were evaluated. In our study, patients with a shorter interval between surgery and RT (≤3 weeks) were found to have a worse prognosis compared with patients with medium and longer intervals (3–6 and ≥6 weeks). It is difficult to draw a definitive conclusion with these results, because no biologic explanation was found and the patient numbers were small. It may be only a coincidence, but needs further investigation.

One-third of our patients received adjuvant chemotherapy. Although no definite scheme or criteria were present for this group, we were not able to show any benefit by adding chemotherapy. Additionally, it is difficult to draw any conclusions from previous reports to show any advantage. The most prominent useful effect of adjuvant chemotherapy was shown in the study from the Royal Marsden Hospital. Patients treated with megavoltage RT and chemotherapy had a 5-year survival rate of 76% compared with 37% after RT alone. However, as they stated, other factors were present that could have contributed to the better survival such as a higher posterior fossa dose, earlier spinal RT, and more total or subtotal resection in the patients who received chemotherapy.

Surgery and postoperative craniospinal RT are the mainstay treatments for adult medulloblastoma patients. Long-term follow-up is necessary, because late recurrences are not rare. Spinal seeding at presentation is a poor prognostic factor for recurrence. The posterior fossa radiation dose must be kept at a minimum of 54 Gy for adequate control. The interval between surgery and the start of RT is an interesting issue that requires further study. The role of adjuvant chemotherapy needs further investigation in prospective multi-institutional studies.