SQL> SELECT 'DROP TABLE ' || T.OWNER || '.' || '"' || T.TABLE_NAME || '" PURGE;' 
AS DROP_ORPHANED_MDRTS_COMMAND
  FROM DBA_TABLES T
 WHERE     T.TABLE_NAME LIKE 'MDRT%'
       AND T.TABLE_NAME NOT IN (SELECT SM.SDO_INDEX_TABLE
                                  FROM ALL_SDO_INDEX_METADATA SM);