1216 Radiation Oncology 0 Biology 0 Physics

25 CEREBELLAR MEDULLOBLASTOMA

fkptember 1981, Volume 7, Number 9

Craig Silverman, M.D., Joseph R. Simpson, M.D.

Washington University School of Medicine Ciallinckrodt Institute of Radioloqy

Division of Radiation Oncology St. Louis, Missouri 63108

The records of 46 patients with cerebellar medulloblastoma treated at our institution between 1954 and 1977 were analyzed for prognostic features, tumor control, patterns of failure and NED survival followina suraical resection and radiation therapy. Three-year and five-year NED s&viva1 was 48% and 42%. Tumor was controlled in the posterior fossa in 52% of all patients. Eighty-five percent of local failures occurred within three years of treatment. All spinal axis failures were associated with concomitant posterior fossa failure whereas all extra-nervous system metastases, i.e., to bones and lymph nodes occurred in patients whose primary tumor was controlled. There were seven (7) patients with cerebral failures of which five (5) failed solely in the brain, three of five in periventricular locations, two of five in the frontal lobes. These were usually late failures.

Those patients receiving at least 4500 rad to the posterior fossa had a local control rate of 63% while those receiving less than 4500 rad had a con- 'trol rate of 37%. Five-year local control for those receiving greater than 5000 rad to the posterior fossa was 82% (14/17). T staging, as proposed by Harisiadis and Chang, was not found to be of any prognostic significance.

Analysis with regard to technique demonstrated that when the posterior fossa was adequately covered with lateral fields that extended below the level of foramen magnum, the five-year survival was 52% versus 26% when the fields were considered inadequate, and local control was 63% versus 45%.

MEDULLOBLASTOMA:

Identification and Implications of Prognostic Subgroups

Gene Kopelson'MD, Rita M. LinggoodlMD, George M. Kleinman2MD

'Department of Radiation Medicine and 2Neuropathology Laboratory of the Department of Pathology, Massachusetts General Hospital,

Boston, MA 02114

Forty-three medulloblastoma patients seen from 1962-1979 were evaluated for prognostic factors and post-irradiation local control rates as a function of a new histopathologic subclassification scheme (TS=Tumor Score, a function of necrosis, desmoplasia, mitoses, and cytoplasmic processes), TM operative staging, as well as classical clinical parameters.

An overall actuarial 5-and lo-year survival rate of 55% was achieved. Factors from the literature which previously have had prognostic

importance (age. sex) did not affect prognosis in this series. -The most siqnificant parameters wern staqe and TS. Five-year survival rates were better for: low T-stage (82% Tl,2_vs 46% T3,4, P <5.02), low M-stage (63% MO.1 vs. 0% M2,3, P < 0.03), and favorable histopathologic subtype (81% TS < 5 vs 41% TS > 6, P ~0.05). Posterior fossa local control rates post- irrzdiation were a function of T-stage (90% T1.2 vs 38% T3,4), and histology (83% TS < 5 vs 38% TS > 6). Combining T-stage and TS resulted in 3 major prognostic and local-cZntro1 groups:

Small (Tl,2) tumors of favorable histology (TS < 5) had a 5-and lo-year survival of 92% with 100% (8/8) local control, No change from present management is suggested.

An intermediate prognosis (survival rates of 67% and 70%, respectively) was found for small tumors (Tl,2) of unfavorable histology (TS > 6) and for large tumors (T3,4) of favorable histology (TS < 5). These patTents showed evidence of an irradiation dose-response; local-control was achieved in O/3 receiving < 5000 rad vs 3/3 receiving > 5000 rad. In this group, by only increasing the posterior fossa dose; Improved survival may-result..

The poor proanosis arouo (T3.4-TS > 6) had a 5-vear survival of onlv 42% and increasing-the poiterior fossa doze to > 5000 rad did not increase- local control. It is suggested that patients for future adjuvant chemotherapy or radiosensitizer trials be selected from this poor risk group of patients with large and/or necrotic tumors.