Grade @ or @ neutropenia was significantly more frequent with high-dose melphalan than with MPR ( @ % vs. @ % ) , as were gastrointestinal adverse events ( @ % vs. @ % ) and infections ( @ % vs. @ % ) ; neutropenia and dermatologic toxic effects were more frequent with lenalidomide maintenance than with no maintenance ( @ % vs. @ % and @ % vs. @ % , respectively ) .