Predictors of Free Flap Volume Loss in Nonosseous Reconstruction of Head and Neck Oncologic Defects

Objectives: Free tissue reconstruction of the head and neck must be initially overcorrected due to expected postoperative free flap volume loss, which can be accelerated by adjuvant radiation therapy. In this study, we aim to identify patient and treatment-specific factors that may significantly contribute to this phenomenon and translate these characteristics into a predictive model for expected percent free flap volume loss in a given patient. Methods: Patients with a history of oral cavity and/or oropharyngeal cancer who underwent nonosseous free flap reconstruction were reviewed between January 2009 and November 2018 at a tertiary care center. Demographics/characteristics, total radiation dose, radiation fractionation (RF), and pre/postradiation free flap volume as evaluated by computed tomography imaging were collected. Free flap volume was measured by a fellowship-trained neuroradiologist in all cases. Only patients receiving adjuvant radiotherapy with available pre/postradiation imaging were included. Multivariable linear regression modeling for prediction of free flap volume loss was performed with optimization via stepwise elimination. Results: Thirty patients were included for analysis. Mean flap volume loss was 42.7% +/- 17.4%. The model predicted flap volume loss in a significant fashion (P = .004, R-2 = 0.49) with a mean magnitude of error of 9.8% +/- 7.5%. Age (beta = 0.01, P = .003) and RF (beta = -0.01, P = .009) were individual predictors of flap volume loss. Conclusions: Our model predicts percent free flap volume loss in a significant fashion. Age and RF are individual predictors of free flap volume loss, the latter being a novel finding that is also modifiable through hyperfractionation radiotherapy schedules.