After the report execution when user press 'Back' button the selection-screen is displayed with the values entered in first place. If you want the selection-screen to be all clear then add following lines of code at the end of END-OF-SELECTION event.
FIELD-SYMBOLS : <fs> .ASSIGN ('(RSDBRUNT)MEMKEY-INT_MODE') TO <fs> .
IF sy-subrc = 0 .
<FS> = '01' .