MEDULLOBLASTOMA - THE DUKE-UNIVERSITY MEDICAL-CENTER EXPERIENCE

We have reviewed the clinical experience in the treatment of medulloblastoma with radiotherapy at Duke University Medical Center. One hundred and twenty-seven patients treated between January 1, 1940 and December 31, 1983 were evaluated. The irradiation technique was reviewed and all irradiation doses were recalculated at minimum tumor doses in Gray (Gy). The mean follow-up was 24.4 years and the median followup was 26.5 years. The energy of the treatment machine was known in 102 cases. Sixty patients were treated with orthovoltage equipment and 42 patients were treated with megavoltage equipment. As a gross assessment of the impact of the details of radiotherapy treatment upon outcome, patients were grouped into excellent, good, fair, and poor treatment groups. Patients undergoing cranio-spinal axis (CSA) irradiation and receiving .gtoreq. 52 Gy to the posterior fossa and .gtoreq. 30 Gy to the clinically uninvolved remainder of the CSA were classified as having "excellent" technique. Patients undergoing CSA irradiation and receiving 40 to 52 Gy to the posterior fossa and .gtoreq. 20 Gy to the remainder of the CSA were classified as "good". Patients receiving 20 to 40 Gy to the posterior fossa and .gtoreq. 10 Gy to the spinal axis with or without prophylactic cranial irradiation were designated "fair". Any patient not fulfilling the above minimum criteria was categorized as "poor". The actuarial 5-year survival for the entire population was 33%. The 10-year survival was 21%. In 93 patients for whom records were detailed enough to allow categorization of treatment technique, 5-year actuarial survivals were: Excellent 37% (n = 17), Good 55% (n = 13), Fair 35% (n = 23), Poor 20% (n = 40). A complete surgical resection was not correlated with improved disease-free survival (DFS) in the excellent and good groups, but was correlated with an improved DFS in the fair and poor groups. The posterior fossa accounted for 62% of the failures in the 55 patients completing irradiation where the initial site of failure was known. An examination of patterns of failures in the spinal canal failed to demonstrate a dose response relationship above 10 Gy for spinal canal prophylactic irradiation. No patient developed recurrence beyond their period of risk as defined by "Collins'' Law". In multivariable analysis, three factors were found to be independently associated with freedom from relapse: Radiation technique (p = 0.02, good/excellent > fair > poor), extent of resection (p = 0.04, total > subtotal or biopsy), and Chang T stage (p = 0.03, Stage IV > Stage III > Stage II). The last finding ran counter to expectation and indicates the inadequacy of staging patients retrospectively. The decade of treatment and the treatment machine energy were highly correlated with the treatment technique quality and were eliminated as independent factors in the multivariable analysis. We conclude: (a) Survival appears to be partially correlated with improved radiotherapy technique. (b) Spinal cord prophylaxis with irradiation in standard risk patients will need to be examined by prospective randomized trials to assess whether this dose can be lowered and thus decrease morbidity. (c) The period of risk for recurrence as defined by "Collins'' Law" was valid in our population.