Medical charts for each of the eligible patients were reviewed to obtain clinical staging, treatment, and comorbidity information. Staging was classified according to TNM criteria. Medical comorbidities were classified according to a modification of the Kaplan Feinstein comorbidity index (the 27-item Adult Comorbidity Evaluation comorbidity index [ACE-27]), which reflects the presence of related comorbidities as “none” to “mild,” “moderate,” or “severe.”17 This comorbidity index has been demonstrated to be an independent prognostic factor for patients with head and neck cancer.17,18 In addition, smoking history and alcohol exposure were assessed using epidemiologic questionnaires completed by all patients on enrollment to the parent molecular epidemiologic study. Patients who had smoked more than 100 cigarettes in their lifetimes were classified as smokers, and those who had quit smoking more than 1 year prior to enrollment in the study were classified as former smokers. Patients who used alcohol at least once a week for more than 1 year were classified as drinkers, and those who had quit such alcohol use more than 1 year prior to enrollment were classified as former drinkers. Treatment information, including site and extent of resection and type of flap used, was also recorded. All cases were reviewed for the development of surgical complications at both the donor and recipient sites, including wound infection, wound dehiscence, hematoma, seroma, fistula formation, flap failure, partial flap loss, and flap thrombosis. The development of medical complications was also recorded for each patient, including pneumonia, myocardial infarction, cardiac arrhythmias, and renal failure. Patients who received prior radiotherapy to the head and neck were excluded from this study.