title: Using multivariate regression model with least absolute shrinkage and selection operator (LASSO) to predict the incidence of Xerostomia after intensity-modulated radiotherapy for head and neck cancer.
abstract: OBJECTIVE
  The aim of this study was to develop a multivariate logistic regression model with least absolute shrinkage and selection operator (LASSO) to make valid predictions about the incidence of moderate-to-severe patient-rated xerostomia among head and neck cancer (HNC) patients treated with IMRT.
  
  
  METHODS
  Quality of life questionnaire datasets from 206 patients with HNC were analyzed. The European Organization for Research and Treatment of Cancer QLQ-H&N35 and QLQ-C30 questionnaires were used as the endpoint evaluation. The primary endpoint (grade 3(+) xerostomia) was defined as moderate-to-severe xerostomia at 3 (XER3m) and 12 months (XER12m) after the completion of IMRT. Normal tissue complication probability (NTCP) models were developed. The optimal and suboptimal numbers of prognostic factors for a multivariate logistic regression model were determined using the LASSO with bootstrapping technique. Statistical analysis was performed using the scaled Brier score, Nagelkerke R(2), chi-squared test, Omnibus, Hosmer-Lemeshow test, and the AUC.
  
  
  RESULTS
  Eight prognostic factors were selected by LASSO for the 3-month time point: Dmean-c, Dmean-i, age, financial status, T stage, AJCC stage, smoking, and education. Nine prognostic factors were selected for the 12-month time point: Dmean-i, education, Dmean-c, smoking, T stage, baseline xerostomia, alcohol abuse, family history, and node classification. In the selection of the suboptimal number of prognostic factors by LASSO, three suboptimal prognostic factors were fine-tuned by Hosmer-Lemeshow test and AUC, i.e., Dmean-c, Dmean-i, and age for the 3-month time point. Five suboptimal prognostic factors were also selected for the 12-month time point, i.e., Dmean-i, education, Dmean-c, smoking, and T stage. The overall performance for both time points of the NTCP model in terms of scaled Brier score, Omnibus, and Nagelkerke R(2) was satisfactory and corresponded well with the expected values.
  
  
  CONCLUSIONS
  Multivariate NTCP models with LASSO can be used to predict patient-rated xerostomia after IMRT.
authors.affiliation: Medical Physics and Informatics Laboratory of Electronics Engineering, National Kaohsiung University of Applied Sciences, Kaohsiung, Taiwan, ROC.
authors.forename: Tsair-Fwu
authors.initials: TF
authors.lastname: Lee
authors.affiliation: Department of Radiation Oncology, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung, Taiwan, ROC.
authors.forename: Pei-Ju
authors.initials: PJ
authors.lastname: Chao
authors.affiliation: Department of Radiation Oncology, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung, Taiwan, ROC ; Department of Electrical Engineering, National Kaohsiung University of Applied Sciences, Kaohsiung, Taiwan, ROC.
authors.forename: Hui-Min
authors.initials: HM
authors.lastname: Ting
authors.affiliation: Department of Medical Imaging and Radiological Sciences, I-Shou University, Kaohsiung, Taiwan, ROC.
authors.forename: Liyun
authors.initials: L
authors.lastname: Chang
authors.affiliation: Department of Radiation Oncology, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung, Taiwan, ROC.
authors.forename: Yu-Jie
authors.initials: YJ
authors.lastname: Huang
authors.affiliation: Department of Radiation Oncology, E-Da Hospital, Kaohsiung, Taiwan, ROC.
authors.forename: Jia-Ming
authors.initials: JM
authors.lastname: Wu
authors.affiliation: Department of Electronics Engineering, National Kaohsiung University of Applied Sciences, Kaohsiung, Taiwan, ROC.
authors.forename: Hung-Yu
authors.initials: HY
authors.lastname: Wang
authors.affiliation: Department of Electronics Engineering, National Kaohsiung University of Applied Sciences, Kaohsiung, Taiwan, ROC.
authors.forename: Mong-Fong
authors.initials: MF
authors.lastname: Horng
authors.affiliation: Medical Physics and Informatics Laboratory of Electronics Engineering, National Kaohsiung University of Applied Sciences, Kaohsiung, Taiwan, ROC.
authors.forename: Chun-Ming
authors.initials: CM
authors.lastname: Chang
authors.affiliation: Department of Radiation Oncology, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung, Taiwan, ROC ; Department of Electrical Engineering, National Kaohsiung University of Applied Sciences, Kaohsiung, Taiwan, ROC.
authors.forename: Jen-Hong
authors.initials: JH
authors.lastname: Lan
authors.affiliation: Department of Radiation Oncology, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung, Taiwan, ROC.
authors.forename: Ya-Yu
authors.initials: YY
authors.lastname: Huang
authors.affiliation: Department of Radiation Oncology, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung, Taiwan, ROC.
authors.forename: Fu-Min
authors.initials: FM
authors.lastname: Fang
authors.affiliation: Department of Radiation Oncology, Kaohsiung Yuan's General Hospital, Kaohsiung, Taiwan, ROC.
authors.forename: Stephen Wan
authors.initials: SW
authors.lastname: Leung
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006258:Head and Neck Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011788:Quality of Life; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D011795:Surveys and Questionnaires; D014987:Xerostomia / Q000473:pathology / Q000532:radiotherapy*