title: Functional Data Analysis Applied to Modeling of Severe Acute Mucositis and Dysphagia Resulting From Head and Neck Radiation Therapy.
abstract: Current normal tissue complication probability modeling using logistic regression suffers from bias and high uncertainty in the presence of highly correlated radiation therapy (RT) dose data. This hinders robust estimates of dose-response associations and, hence, optimal normal tissue-sparing strategies from being elucidated. Using functional data analysis (FDA) to reduce the dimensionality of the dose data could overcome this limitation.
  
  
  
  FDA was applied to modeling of severe acute mucositis and dysphagia resulting from head and neck RT. Functional partial least squares regression (FPLS) and functional principal component analysis were used for dimensionality reduction of the dose-volume histogram data. The reduced dose data were input into functional logistic regression models (functional partial least squares-logistic regression [FPLS-LR] and functional principal component-logistic regression [FPC-LR]) along with clinical data. This approach was compared with penalized logistic regression (PLR) in terms of predictive performance and the significance of treatment covariate-response associations, assessed using bootstrapping.
  
  
  
  The area under the receiver operating characteristic curve for the PLR, FPC-LR, and FPLS-LR models was 0.65, 0.69, and 0.67, respectively, for mucositis (internal validation) and 0.81, 0.83, and 0.83, respectively, for dysphagia (external validation). The calibration slopes/intercepts for the PLR, FPC-LR, and FPLS-LR models were 1.6/-0.67, 0.45/0.47, and 0.40/0.49, respectively, for mucositis (internal validation) and 2.5/-0.96, 0.79/-0.04, and 0.79/0.00, respectively, for dysphagia (external validation). The bootstrapped odds ratios indicated significant associations between RT dose and severe toxicity in the mucositis and dysphagia FDA models. Cisplatin was significantly associated with severe dysphagia in the FDA models. None of the covariates was significantly associated with severe toxicity in the PLR models. Dose levels greater than approximately 1.0 Gy/fraction were most strongly associated with severe acute mucositis and dysphagia in the FDA models.
  
  
  
  FPLS and functional principal component analysis marginally improved predictive performance compared with PLR and provided robust dose-response associations. FDA is recommended for use in normal tissue complication probability modeling.
authors: Joint Department of Physics, The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, London, UK. Electronic address: jamie.dean@icr.ac.uk.
authors: Jamie A
authors: JA
authors: Dean
authors: Head and Neck Unit, The Royal Marsden NHS Foundation Trust, London, UK.
authors: Kee H
authors: KH
authors: Wong
authors: Department of Radiation Oncology, School of Medicine, Washington University in St Louis, St Louis, Missouri.
authors: Hiram
authors: H
authors: Gay
authors: Head and Neck Unit, The Royal Marsden NHS Foundation Trust, London, UK.
authors: Liam C
authors: LC
authors: Welsh
authors: Head and Neck Unit, The Royal Marsden NHS Foundation Trust, London, UK.
authors: Ann-Britt
authors: AB
authors: Jones
authors: Head and Neck Unit, The Royal Marsden NHS Foundation Trust, London, UK.
authors: Ulrike
authors: U
authors: Schick
authors: Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, New York.
authors: Jung Hun
authors: JH
authors: Oh
authors: Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, New York.
authors: Aditya
authors: A
authors: Apte
authors: Head and Neck Unit, The Royal Marsden NHS Foundation Trust, London, UK; Division of Radiotherapy and Imaging, The Institute of Cancer Research, London, UK.
authors: Kate L
authors: KL
authors: Newbold
authors: Head and Neck Unit, The Royal Marsden NHS Foundation Trust, London, UK; Division of Radiotherapy and Imaging, The Institute of Cancer Research, London, UK.
authors: Shreerang A
authors: SA
authors: Bhide
authors: Head and Neck Unit, The Royal Marsden NHS Foundation Trust, London, UK; Division of Radiotherapy and Imaging, The Institute of Cancer Research, London, UK.
authors: Kevin J
authors: KJ
authors: Harrington
authors: Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, New York.
authors: Joseph O
authors: JO
authors: Deasy
authors: Head and Neck Unit, The Royal Marsden NHS Foundation Trust, London, UK; Division of Radiotherapy and Imaging, The Institute of Cancer Research, London, UK.
authors: Christopher M
authors: CM
authors: Nutting
authors: Joint Department of Physics, The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, London, UK.
authors: Sarah L
authors: SL
authors: Gulliford
mesh_terms: D000208:Acute Disease; D019540:Area Under Curve; D016190:Carboplatin / Q000009:adverse effects; D002945:Cisplatin / Q000009:adverse effects; D003680:Deglutition Disorders / Q000209:etiology*; D004307:Dose-Response Relationship, Radiation; D006258:Head and Neck Neoplasms / Q000532:radiotherapy*; D006801:Humans; D015233:Models, Statistical; D052016:Mucositis / Q000209:etiology*; D058958:Organs at Risk / Q000528:radiation effects*; D025341:Principal Component Analysis; D012372:ROC Curve; D011832:Radiation Injuries / Q000150:complications*; D011838:Radiation-Sensitizing Agents / Q000009:adverse effects; D011879:Radiotherapy Dosage; D012044:Regression Analysis
chemical_list: D011838:Radiation-Sensitizing Agents; D016190:Carboplatin; D002945:Cisplatin