GSTM1 and neoplasm: (2) Regression analysis showed that independent risk factors for perioperative transfusion included the following: BMI, tumor T3–T4 stage, ASA III, IV grade, and free flap/pediculated flap/bone flap in patients with different Hb levels; T3–T4 stage, ASA grade III–IV in mildly anemic patients; and ASA grade III–IV in moderately anemic patients.