major surgery recovered effects starting weeks prior study patient fully intra thoracic surgery abdominal injury pelvic major starting procedure effects starting weeks received effects therapy drug study recovered prior nitrosourea surgery radiation therapy weeks treatment major chemotherapy prior study recovered major traumatic injury surgery significant study effects recovered days weeks effects surgery recovered major undergone starting weeks drug prior study complications recovered adequately toxicity intervention major surgery starting prior therapy major surgery weeks planned study prior elective course starting treatment effects recovered surgery radiotherapy prior recent antineoplastic patients therapy chemotherapy