title: Change in the growth rate of localized pancreatic adenocarcinoma in response to gemcitabine, bevacizumab, and radiation therapy on MDCT.
abstract: OBJECTIVE
  To depict treatment response to chemoradiotherapy by comparing tumor growth rate between treated and untreated patients and to compare depicted response with objective response according to the Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 guideline.
  
  
  METHODS
  This Health Insurance Portability and Accountability Act-compliant, retrospective study was approved by the institutional review board. Volume doubling time (DT) of histologically confirmed locally advanced pancreatic adenocarcinoma was calculated in 16 patients treated with chemoradiotherapy and 10 untreated patients by incorporating interscan interval (Δt) and tumor volume at baseline (V0) and follow-up (V1) obtained by semiautomated segmentation into the following equation: DT = Δt · log 2/log (V1/V0). Reciprocal of doubling time (RDT), which is the linear representation of tumor growth rate, was calculated by use of the following equation: RDT = 365/DT. The lowest RDT value of 2.42 in untreated patients was considered as the cutoff value for depiction of treatment response. Depicted response rate was defined as the proportion of patients with an RDT value of less than 2.42. Depicted response was compared with objective response according to the RECIST 1.1 guideline. The significance level was set at p < 0.05.
  
  
  RESULTS
  There was a significant difference in mean RDT between treated (range, -7.12 to 3.27; mean, -1.27; median, -1.30) and untreated (range, 2.42 to 10.74; mean, 5.33; median, 4.26) patients (p < 0.05). Reciprocal of doubling time was less than 2.42 in 14 treated patients, which corresponded to a depicted response rate of 87.50% as opposed to the objective response rate of 18.75% according to the RECIST 1.1 guideline (p < 0.05) and carbohydrate antigen 19-9 response rate of 62.50% (p > 0.05). Carbohydrate antigen 19-9 response was concordant with RDT and RECIST response in 12 patients (75.00%) (κ, 0.38) and 9 patients (56.25%) (κ, 0.24), respectively.
  
  
  CONCLUSIONS
  There was a significant difference between depicted response according to RDT and objective response according to RECIST. Reciprocal of doubling time might serve as a valuable biomarker for evaluation of treatment response when depiction of small changes in tumor size is concerned.
authors.affiliation: Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA.
authors.forename: Pedram
authors.initials: P
authors.lastname: Rezai
authors.forename: Vahid
authors.initials: V
authors.lastname: Yaghmai
authors.forename: Sandra M
authors.initials: SM
authors.lastname: Tochetto
authors.forename: Mauricio S
authors.initials: MS
authors.lastname: Galizia
authors.forename: Frank H
authors.initials: FH
authors.lastname: Miller
authors.forename: Mary F
authors.initials: MF
authors.lastname: Mulcahy
authors.forename: William
authors.initials: W
authors.lastname: Small
mesh_terms: D000368:Aged; D000911:Antibodies, Monoclonal / Q000008:administration & dosage; D061067:Antibodies, Monoclonal, Humanized; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D000068258:Bevacizumab; D018395:CA-19-9 Antigen / Q000097:blood; D021441:Carcinoma, Pancreatic Ductal / Q000188:drug therapy* / Q000473:pathology / Q000532:radiotherapy*; D003841:Deoxycytidine / Q000008:administration & dosage / Q000031:analogs & derivatives; D004334:Drug Administration Schedule; D005260:Female; D019983:Guideline Adherence; D006801:Humans; D008297:Male; D008875:Middle Aged; D010190:Pancreatic Neoplasms / Q000188:drug therapy* / Q000473:pathology / Q000532:radiotherapy*; D012189:Retrospective Studies; D013997:Time Factors; D016896:Treatment Outcome; D047368:Tumor Burden / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D000093542:Gemcitabine
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D018395:CA-19-9 Antigen; D003841:Deoxycytidine; D000068258:Bevacizumab; D000093542:Gemcitabine